Disinfezione (aprile 2003 - aprile 2012)

Control of Legionella contamination in a hospital water distribution system by monochloramine

Marchesi I, Cencetti S, Marchegiano P, Frezza G, Borella P, Bargellini A.

Department of Public Health Sciences, University of Modena and Reggio Emilia, Modena, Italy. annalisa.bargellini@unimore.it

Am J Infect Control. 2012 Apr;40(3):279-81.

ABSTRACT: BACKGROUND: We report the results of 1-year application of monochloramine to control Legionella pneumophila contamination in a hospital hot water distribution system. METHODS: In the main building of the hospital, a device continuously distributing monochloramine was installed. Legionella pneumophila and Pseudomonas spp contamination was followed in comparison with 2 other water networks in the same building using chlorine dioxide. RESULTS: Monochloramine significantly reduced the number of contaminated sites compared with baseline (from 97.0% to 13.3%, respectively), chlorine dioxide device I (from 100% to 56.7%, respectively), and device II (from 100% to 60.8%, respectively). No positive sample exceeded 10(4) colony-forming units/L versus 59.4% at baseline. CONCLUSION: Monochloramine could represent a good alternative to chlorine dioxide in controlling legionellae contamination in public and private buildings.


Legionella pneumophila transcriptional response to chlorine treatment

Bodet C, Sahr T, Dupuy M, Buchrieser C, Héchard Y.

Laboratoire de Chimie et Microbiologie de l'Eau, UMR 6008, Université de Poitiers, 40 avenue du Recteur Pineau, 86022 Poitiers Cedex, France. charles.bodet@univ-poitiers.fr

Water Res. 2012 Mar 1;46(3):808-16.

ABSTRACT: Legionella pneumophila is a ubiquitous environmental microorganism found in freshwater that can cause an acute form of pneumonia known as Legionnaires' disease. Despite widespread use of chlorine to ensure drinking water quality and awareness that L. pneumophila may escape these treatments, little is known about its effects on L. pneumophila. The aim of this study was to investigate the L. pneumophila transcriptional response induced by chlorine treatment. Transcriptome analysis, using DNA arrays, showed that a sublethal dose of chlorine induces a differential expression of 391 genes involved in stress response, virulence, general metabolism, information pathways and transport. Many of the stress response genes were significantly upregulated, whereas a significant number of virulence genes were repressed. In particular, exposure of L. pneumophila to chlorine induced the expression of cellular antioxidant proteins, stress proteins and transcriptional regulators. In addition, glutathione S-transferase specific activity was enhanced following chlorine treatment. Our results clearly indicate that chlorine induces expression of proteins involved in cellular defence mechanisms against oxidative stress that might be involved in adaptation or resistance to chlorine treatment.


Chemical disinfection of Legionella in hot water systems biofilm: a pilot-scale 1 study

Farhat M, Trouilhé MC, Forêt C, Hater W, Moletta-Denat M, Robine E, Frère J.

Centre Scientifique et Technique du Bâtiment, 84 avenue Jean Jaurès, Champs-sur-Marne, 77447 Marne-la-Vallée cedex 02, France. jacques.frere@univ-poitiers.fr

Water Sci Technol. 2011;64(3):708-14.

ABSTRACT: Legionella bacteria encounter optimum growing conditions in hot water systems and cooling towers. A pilot-scale 1 unit was built in order to study the biofilm disinfection. It consisted of two identical loops, one used as a control and the other as a 'Test Loop'. A combination of a bio-detergent and a biocide (hydrogen peroxide + peracetic acid) was applied in the Test Loop three times under the same conditions at 100 and 1,000 mg/L with a contact time of 24 and 3-6 hours, respectively. Each treatment test was preceded by a three week period of biofilm re-colonization. Initial concentrations of culturable Legionella into biofilm were close to 10(3) CFU/cm2. Results showed that culturable Legionella spp. in biofilm were no longer detectable three days following each treatment. evertheless, initial Legionella spp. concentrations were recovered 7 days after the treatments (in two cases). Before the tests, Legionella spp. and L. pneumophila PCR counts were both about 10(4) GU/cm2 in biofilm and they both decreased by 1 to 2 log units 72 hours after each treatment. The three tests had a good but transient efficiency on Legionella disinfection in biofilm.


Prevention of Legionnaires' disease in hospitals

Sarjomaa M, Urdahl P, Ramsli E, Borchgrevink-Lund CF, Ask E.

Medical Clinic, Telemark Central Hospital, Skien, Norway. marjut.anneli.sarjomaa@sthf.no

Tidsskr Nor Laegeforen. 2011 Aug 23;131(16):1554-7.

ABSTRACT: BACKGROUND: The first instance of Legionella infection in a Norwegian hospital was confirmed in 2005. We describe the best-known methods of eradicating Legionella in hospitals.

MATERIALS AND METHOD: The article is based on the authors' experience of measures to prevent Legionnaires' disease in hospitals and on a non-systematic search in PubMed. RESULTS: There are several methods of combating Legionella in hospitals. These include chlorination, heat treatment, and the use of filters. However, recontamination easily re-occurs after eradication. The silver and copper ionisation treatment of water is a well-documented method for the systematic and long-term eradication of Legionella in water. The disadvantages of this method are that it is expensive, that there is a risk of discolouring the water, and that there is a possibility of developing resistance in environmental bacteria. This resistance mechanism can theoretically be transferred to bacteria that cause illness. INTERPRETATION: We recommend the silver and copper ionisation treatment of water as a method of preventing nosocomial Legionnaires' disease when standard methods fail and there is a high prevalence of Legionella in the water. The discolouration of operation instruments that occurs as a result of high silver concentrations can be avoided by using a separate water supply for operation units.


Effectiveness of different methods to control legionella in the water supply: ten-year experience in an Italian university hospital

Marchesi I, Marchegiano P, Bargellini A, Cencetti S, Frezza G, Miselli M, Borella P.

Department of Public Health Sciences, University of Modena and Reggio Emilia, Italy.

J Hosp Infect. 2011 Jan;77(1):47-51. paola.borella@unimore.it

ABSTRACT: We report our ten-year experience of hyperchlorination, thermal shock, chlorine dioxide, monochloramine, boilers and point-of-use filters for controlling legionella contamination in a hospital hot water distribution system. Shock disinfections were associated with a return to pre-treatment contamination levels within one or two months. We found that chlorine dioxide successfully maintained levels at <100cfu/L, whilst preliminary experiments gave satisfactory results with monochloramine. No contamination was observed applying point-of-use filters and electric boilers at temperatures of >58°C and no cases of nosocomial legionellosis were detected in the ten-year observation period. Our performance ranking in reducing legionella contamination was filter, boiler, chlorine dioxide, hyperchlorination and thermal shock. Chlorine dioxide was the least expensive procedure followed by thermal shock, hyperchlorination, boiler and filter. We suggest adopting chlorine dioxide and electric boilers in parallel.


Efficiency of water disinfectants against Legionella pneumophila and Acanthamoeba

Dupuy M, Mazoua S, Berne F, Bodet C, Garrec N, Herbelin P, Ménard-Szczebara F, Oberti S, Rodier MH, Soreau S, Wallet F, Héchard Y.

Université de Poitiers, Laboratoire de Chimie et Microbiologie de l'Eau, CNRS UMR 6008, 40 avenue du recteur Pineau, 86022 Poitiers Cedex, France. yann.hechard@univ-poitiers.fr

Water Res. 2011 Jan;45(3):1087-94.

ABSTRACT: Free-living amoebae might be pathogenic by themselves and be a reservoir for bacterial pathogens, such as Legionella pneumophila. Not only could amoebae protect intra-cellular Legionella but Legionella grown within amoebae could undergo physiological modifications and become more resistant and more virulent. Therefore, it is important to study the efficiency of treatments on amoebae and Legionella grown within these amoebae to improve their application and to limit their impact on the environment. With this aim, we compared various water disinfectants against trophozoites of three Acanthamoeba strains and L. pneumophila alone or in co-culture. Three oxidizing disinfectants (chlorine, monochloramine, and chlorine dioxide) were assessed. All the samples were treated with disinfectants for 1 h and the disinfectant concentration was followed to calculate disinfectant exposure (Ct). We noticed that there were significant differences of susceptibility among the Acanthamoeba strains. However no difference was observed between infected and non-infected amoebae. Also, the comparison between the three disinfectants indicates that monochloramine was efficient at the same level towards free or co-cultured L. pneumophila while chlorine and chlorine dioxide were less efficient on co-cultured L. pneumophila. It suggests that these disinfectants should have different modes of action. Finally, our results provide for the first time disinfectant exposure values for Acanthamoeba treatments that might be used as references for disinfection of water systems. 


Effects of chemically and electrochemically dosed chlorine on Escherichia coli and Legionella beliardensis assessed by flow cytometry

Wang Y, Claeys L, van der Ha D, Verstraete W, Boon N.

Laboratory of Microbial Ecology and Technology (LabMET), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium. Nico.Boon@UGent.be

Appl Microbiol Biotechnol. 2010 Jun;87(1):331-41.

ABSTRACT: The present study reports the disinfection effects of chemically and electrochemically dosed chlorine on two models for typical water-borne bacteria (Escherichia coli and Legionella beliardensis) by plating and flow cytometry (FCM) in combination with different fluorescence dyes. The residual effect on various cell functions, including cultivability, esterase activity, membrane polarization, and integrity, was tested at different free chlorine concentrations. In comparison, chemical disinfection yielded on average 60% more E. coli cells entering the viable but nonculturable (VBNC) state than electrochemical disinfection. Here, VBNC is defined as those cells with intact cell membrane but which cannot be cultured on solid nutrient agar plates. L. beliardensis was about five times more resistant to chlorine disinfection than E. coli. The results also suggested the two methods result in different disinfection mechanisms on L. beliardensis, i.e., chemically dosed chlorine targeted cell membrane integrity before enzyme activity, while electrochemically dosed chlorine acted the other way round. In addition, both bacteria lost the integrity of their cell membranes at three times lower chlorine concentration over a longer contact time (i.e., 40 vs. 10 min) by the chemical method. Our results showed that FCM is an appropriate tool to evaluate the effects of water disinfection and the percentage of cells in VBNC in a matter of hours. Electrochemical disinfection is suggested to be a favorable alternative for chemical disinfection.


Photocatalytic treatment of bioaerosols: impact of the reactor design

Josset S, Taranto J, Keller N, Keller V, Lett MC.

Laboratoire des Matériaux, Surfaces et Procédés pour la Catalyse (LMSPC), CNRS, Strasbourg University, 25 rue Becquerel, Strasbourg, France. nkeller@chimie.u-strasbg.fr

Environ Sci Technol. 2010 Apr 1;44(7):2605-11.

ABSTRACT: Comparing the UV-A photocatalytic treatment of bioaerosols contaminated with different airborne microorganisms such as L. pneumophila bacteria, T2 bacteriophage viruses and B. atrophaeus bacterial spores, pointed out a decontamination sensitivity following the bacteria > virus > bacterial spore ranking order, differing from that obtained for liquid-phase or surface UV-A photocatalytic disinfection. First-principles CFD investigation applied to a model annular photoreactor evidenced that larger the microorganism size, higher the hit probability with the photocatalytic surfaces. Applied to a commercial photocatalytic purifier case-study, the CFD calculations showed that the performances of the studied purifier could strongly benefit from rational reactor design engineering. The results obtained highlighted the required necessity to specifically investigate the removal of airborne microorganisms in terms of reactor design, and not to simply transpose the results obtained from studies performed toward chemical pollutants, especially for a successful commercial implementation of air decontamination photoreactors. This illustrated the importance of the aerodynamics in air decontamination, directly resulting from the microorganism morphology.


Detergent-like activity and alpha-helical structure of warnericin RK, an anti-legionella peptide

Verdon J, Falge M, Maier E, Bruhn H, Steinert M, Faber C, Benz R, Héchard Y.

Laboratoire de Chimie et Microbiologie de l'Eau, Unite Mixte de Recherche, Centre National de la Recherche Scientifique 6008, Université de Poitiers, Poitiers, France. yann.hechard@univ-poitiers.fr

Biophys J. 2009 Oct;97(7):1933-40.

ABSTRACT: Warnericin RK is the first antimicrobial peptide known to be active against Legionella pneumophila, a pathogen bacterium that is responsible for severe pneumonia. Strikingly, this peptide displays a very narrow range of antimicrobial activity, almost limited to the Legionella genus, and a hemolytic activity. A similar activity has been described for delta-lysin, a well-known hemolytic peptide of Staphylococci that has not been described as antimicrobial. In this study we aimed to understand the mode of action of warnericin RK and to explain its particular target specificity. We found that warnericin RK permeabilizes artificial membranes in a voltage-independent manner. Osmotic protection experiments on erythrocytes showed that warnericin RK does not form well-defined pores, suggesting a detergent-like mode of action, as previously described for delta-lysin at high concentrations. Warnericin RK also permeabilized Legionella cells, and these cells displayed a high sensitivity to detergents. Depending on the detergent used, Legionella was from 10- to 1000-fold more sensitive than the other bacteria tested. Finally, the structure of warnericin RK was investigated by means of circular dichroism and NMR spectroscopy. The peptide adopted an amphiphilic alpha-helical structure, consistent with the proposed mode of action. We conclude that the specificity of warnericin RK toward Legionella results from both the detergent-like mode of action of the peptide and the high sensitivity of these bacteria to detergents.


The antibacterial activity of fragrance ingredients against Legionella pneumophila

Shimizu I, Isshiki Y, Nomura H, Sakuda K, Sakuma K, Kondo S.

Department of Microbiology, School of Pharmaceutical Sciences, Josai University, Saitama, Japan. kondo@josai.ac.jp

Biol Pharm Bull. 2009 Jun;32(6):1114-7.

ABSTRACT: In the current study we investigated the antibacterial activity of fragrance ingredients against Legionella pneumophila, a causative agent of severe pneumonia. Among the 41 different fragrance ingredients tested, we found that the natural fragrance ingredients oakmoss (OM) and birch tar oil (BT), which contain many components, exhibit potent antibacterial activity. The minimum inhibitory concentration (MIC, % (v/v)) of OM and BT were 0.0020 and 0.0024, respectively and were lower than that of cinnamic aldehyde (0.0078), which has been previously shown to possess high antimicrobial activity. In a time-kill assay of OM and BT at MIC and two times MIC, the colony forming units (CFU) of the microbe were reduced to between 10(-3) to 10(-4) of the original CFU after 1 h co-incubation. After this time, the CFU gradually decreased in number, but remained above detection levels even after a 48-h co-incubation, except for BT at two times MIC. In contrast, at a concentration of 0.1% OM and BT (approximately 50 times MIC), CFU were not detected after co-incubation for 1 h. Another 18 fragrance ingredients including ketone, aldehyde, lactone, acid, phenol derivative, aliphatic alcohol and quinoline also exhibited a lesser degree of antibacterial activity against L. pneumophila at a MIC of less than 0.10.


Biofilm problems in dental unit water systems and its practical control

Coleman DC, O'Donnell MJ, Shore AC, Russell RJ.

Microbiology Research Unit, Division of Oral Biosciences, Dublin Dental School & Hospital, University of Dublin, Trinity College Dublin, Lincoln Place, Dublin 2, Ireland. david.coleman@dental.tcd.ie

J Appl Microbiol. 2009 May;106(5):1424-37.

ABSTRACT: Dental chair units (DCUs) contain integrated systems that provide the instruments and services for a wide range of dental procedures. DCUs use water to cool and irrigate DCU-supplied instruments and tooth surfaces during dental treatment. Water is supplied to these instruments by a network of interconnected narrow-bore (2-3 mm) plastic tubes called dental unit waterlines (DUWLs). Many studies over the last 40 years demonstrated that DUWL output water is often contaminated with high densities of micro-organisms, predominantly Gram-negative aerobic heterotropic environmental bacteria, including Legionella and Pseudomonas species. Untreated DUWLs host biofilms that permit micro-organisms to multiply and disperse through the water network and which are aerosolized by DCU instrument use, thus exposing patients and staff to these micro-organisms, to fragments of biofilm and bacterial endotoxins. This review concentrates on how practical developments and innovations in specific areas can contribute to effective DUWL biofilm control. These include the use of effective DUWL treatment agents, improvements to DCU supply water quality, DCU design changes, development of automated DUWL treatment procedures that are effective at controlling biofilm in the long-term and require minimal human intervention, are safe for patients and staff, and which do not cause deterioration of DCU components following prolonged use.


Determination of Legionella pneumophila susceptibility to Melaleuca alternifolia Cheel (tea tree) oil by an improved broth micro-dilution method under vapour controlled conditions

Mondello F, Girolamo A, Scaturro M, Ricci ML.

Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena, 299-00161 Roma, Italy. francesca.mondello@iss.it

J Microbiol Methods. 2009 May;77(2):243-8.

ABSTRACT: The aim of this study was to determine the in vitro activity of Melaleuca alternifolia Cheel (tea tree) oil (TTO) against 22 strains of Legionella pneumophila of different serogroup and source of isolation. Both a standard broth micro-dilution method, with slight modifications, and a micro-atmosphere diffusion method were used. Furthermore, we have established a simple sealing procedure in the micro-dilution method to determine the antibacterial activity of TTO against Legionella in aqueous phase. The results showed that L. pneumophila, quite irrespective of serogroup and source of isolation, is exquisitely sensitive to TTO, with minimal inhibitory concentration (MIC) ranging from 0.125 to 0.5% v/v, and a bactericidal activity at 0.5% v/v. In addition, we show here that TTO vapours exert critical activity, that must be controlled for reproducible MIC determinations. Overall, our data suggest that TTO could be active as anti-Legionella disinfectant, for control of water system contamination, especially in spas, in small waterlines or in particular respiratory medical devices.


The efficacy of biocides and other chemical additives in cooling water systems in the control of amoebae

Critchley M, Bentham R.

CSIRO Materials Science and Engineering, Clayton, VIC 3168, Australia. richard.bentham@flinders.edu.au

J Appl Microbiol. 2009 Mar;106(3):784-9.

ABSTRACT: AIMS: In vitro experiments were undertaken to evaluate biocide formulations commonly used in cooling water systems against protozoa previously isolated from cooling towers. The investigations evaluated the efficacy of these formulations against amoebic cysts and trophozoites. METHODS AND RESULTS: Laboratory challenges against protozoa isolated from cooling towers using chlorine, bromine and isothiazolinone biocides showed that all were effective after 4 h. The presence of molybdate and organic phosphates resulted in longer kill times for bromine and isothiazolinones. All treatments resulted in no detectable viable protozoa after 4 h of exposure. CONCLUSIONS: The chemical disinfection of planktonic protozoa in cooling water systems is strongly influenced by the residence time of the formulation and less so by its active constituent. Bromine and isothiazolinone formulations may require higher dosage of concentrations than currently practiced if used in conjunction with molybdate- and phosphate-based scale/corrosion inhibitors. SIGNIFICANCE AND IMPACT OF THE STUDY: Cooling water systems are complex microbial ecosystems in which predator-prey relationships play a key role in the dissemination of Legionella. This study demonstrated that at recommended dosing concentrations, biocides had species-specific effects on environmental isolates of amoebae that may act as reservoirs for Legionella multiplication in cooling water systems.


Influence of pH on bioactivity of cinnamon oil against Legionella pneumophila and its disinfection efficacy in hot springs

Chang CW, Chang WL, Chang ST.

Institute of Environmental Health, College of Public Health, National Taiwan University, Room 740, 7F, No. 17, Xuzhou Road, Taipei 100, Taiwan, Republic of China. chingwenchang@ntu.edu.tw

Water Res. 2008 Dec;42(20):5022-30.

ABSTRACT: Cinnamon oil extracted from leaves of Cinnamomum osmophloeum has recently been proved as a promising antibacterial agent against Legionella pneumophila, an etiological agent of human pneumonia known as Legionnaires' disease. However, the pH effects on the efficacy of cinnamon oil against L. pneumophila and its applicability to recreational spring water remain unknown. We therefore determined the bactericidal activity of cinnamon oil at pH 3-10 in phosphate-buffered saline (PBS) and in four kinds of springs with various conductivity (259-5595 micros cm(-1)) and pH (2.1-7.7) levels. Results show L. pneumophila cells were more susceptible to cinnamon oil at pH 8-10 than at pH 4-6 in PBS, which became more evident as increasing contact time from 10 to 60 min. An increase in concentration of cinnamon oil and contact time significantly increased the anti-L. pneumophila activity (P< or =0.001), indicating a consistent biocidal effect regardless of pH. Interestingly, this dose-response biocidal effect was also observed in spring waters. Moreover, L. pneumophila of 4 log CFU ml(-1) in spring waters was completely inactivated within 60 min by cinnamon oil at 300-750 microg ml(-1), with the highest inactivation in alkaline hydrogen carbonate spring. The great bioactivity of cinnamon oil demonstrates its potential to be used to control Legionella growth in recreational spring water and possibly other niches generally at basic pH, e.g., cooling towers.


Long-term survival of Legionella pneumophila in the viable but nonculturable state after monochloramine treatment

Alleron L, Merlet N, Lacombe C, Frère J.

Laboratoire de Chimie et de Microbiologie de l'Eau, University of Poitiers, 86022, Poitiers Cedex, France.


Curr Microbiol. 2008 Nov;57(5):497-502.

ABSTRACT: Legionella pneumophila, a facultative intracellular human pathogen, can persist for long periods in natural and artificial aquatic environments. Eradication of this bacterium from plumbing systems is often difficult. We tested L. pneumophila survival after monochloramine treatment. Survival was monitored using the BacLight Bacterial Viability Kit (Molecular Probes), ChemChrome V6 Kit (Chemunex), quantitative polymerase chain reaction and culturability on buffered charcoal-yeast extract agar. In nonculturable samples, regain of culturability was obtained after addition of the amoeba Acanthamoeba castellanii, and esterase activity and membrane integrity were observed after >4 months after treatment. These results demonstrate for the first time that L. pneumophila could persist for long periods in biofilms into the viable but nonculturable (VBNC) state. Monitoring L. pneumophila in water networks is generally done by enumeration on standard solid medium. This method does not take into account VBNC bacteria. VBNC L. pneumophila could persist for long periods and should be resuscitated by amoeba. These cells constitute potential sources of contamination and should be taken into account in monitoring water networks.


Impact of a silver layer on the membrane of tap water filters on the microbiological quality of filtered water

Vonberg RP, Sohr D, Bruderek J, Gastmeier P.

Institute for Medical Microbiology and Hospital Epidemiology, Medical School Hannover, Germany. Vonberg.Ralf@MH-Hannover.de

BMC Infect Dis. 2008 Oct 8;8:133.

ABSTRACT: BACKGROUND: Bacteria in the hospital's drinking water system represent a risk for the acquisition of a nosocomial infection in the severely immunocompromised host. Terminal tap water filters may be used to prevent nosocomial Legionnaires' disease. We present data from water samples using an improved kind of tap water filters. METHODS: In a blinded study on an intermediate care unit of the thoracic surgery department, a modified type of the Germlyser water filter (Aqua-Free Membrane Technology) with a newly-introduced silver layer on the filtration membrane was compared to its preceding type without such a layer on 15 water outlets. We determined growth of Legionella, other pathogenic bacteria, and the total heterotrophic plate count in unfiltered water and filtered water samples after filter usage intervals of 1 through 4 weeks. RESULTS: A total of 299 water samples were tested. Twenty-nine of the 60 unfiltered water samples contained Legionella of various serogroups (baseline value). In contrast, all samples filtered by the original water filter and all but one of the water samples filtered by the modified filter type remained Legionella-free. No other pathogenic bacteria were detected in any filtered sample. The total plate count in water samples increased during use of both kinds of filters over time. However, for the first 7 days of use, there were significantly fewer water samples containing >100 CFU per mL when using the new filter device compared with the older filters or taps with no filter. No advantage was seen thereafter. CONCLUSION: The use of this type of terminal water filter is an appropriate method to protect immunocompromised patients from water-borne pathogens such as Legionella.


Long-term persistence of a single Legionella pneumophila strain possessing the mip gene in a municipal shower despite repeated cycles of chlorination

Cooper IR, White J, Mahenthiralingam E, Hanlon GW.

School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, UK. i.cooper@bton.ac.uk

J Hosp Infect. 2008 Oct;70(2):154-9.

ABSTRACT: The ability of Legionella pneumophila to colonise domestic water systems is a primary cause of outbreaks of Legionnaire's disease in humans. World Health Organization guidelines recommend that drinking water is chlorinated to between 0.2 and 1mg/L [Chlorine in drinking-water. Guidelines for drinking-water quality, 2nd edn. Geneva: World Health Organization; 1996], but L. pneumophila is repeatedly isolated from chlorinated water systems, indicating that this treatment is not effective at preventing colonisation. Current UK guidelines recommend a one-off treatment of 20-50mg/L of free chlorine to remove the bacteria. In this study we report on the persistence of L. pneumophila serogroup 1 in a domestic shower system despite repeated cycles of chlorination at 50mg/L for 1h exposure time, over the course of two and a half years. Persisting isolates were subjected to in-vitro phenotypic analyses and polymerase chain reaction analysis for the toxin-encoding mip gene. Random amplified polymorphic DNA typing was also performed to determine whether the isolates recovered on different occasions were the same strain. We found that seven isolates of L. pneumophila recovered over a two-and-a-half year period are the same genetically defined strain, indicating that the bacteria can persist despite repeated cycles of chlorination after each successive isolation.


Persistence of chlorine-sensitive Legionella pneumophila in hyperchlorinated installations

García MT, Baladrón B, Gil V, Tarancon ML, Vilasau A, Ibañez A, Elola C, Pelaz C.

Laboratorio de Legionella, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain. cpelaz@isciii.es

J Appl Microbiol. 2008 Sep;105(3):837-47.

ABSTRACT: AIMS: To study the persistence of Legionella over time in different disinfected facilities and analysing whether failures in bacterial eradication could be the result of a decrease in the susceptibility of the persistent strains to subsequent treatments. METHODS AND RESULTS: A long-term environmental surveillance was carried out in three different facilities associated with cases of Legionnaires' disease (a hospital, a fishing boat and a hotel). Despite several hyperchlorination episodes, amplified fragment length polymorphism, pulsed field gel electrophoresis-SfiI and arbitrarily primed polymerase chain reaction methods demonstrated that a specific clone of L. pneumophila serogroup 1 was able to survive for 17, 5 and 10 years in the hospital, fishing boat and the hotel, respectively. Isolates from different years from the same facility showed similar minimal inhibitory concentration and minimal bactericidal concentration values against eight different disinfectants. CONCLUSIONS: Hyperchlorination over long periods of time did not prevent the persistence of L. pneumophila. The lack of effectiveness did not appear to be the result of a decreased susceptibility of Legionella to chlorine. Hyperchlorination did not modify in vitro susceptibility of Legionella to other disinfectants to which the bacteria had not previously been exposed. SIGNIFICANCE AND IMPACT OF THE STUDY: Persistent Legionella in treated installations remain sensitive to disinfectants; hence, new strategies of treatment, different from hyperchlorination, should be developed to achieve bacterial eradication.


Molecular epidemiology of Legionella pneumophila serogroup 1 isolates following long-term chlorine dioxide treatment in a university hospital water system

Casini B, Valentini P, Baggiani A, Torracca F, Frateschi S, Nelli LC, Privitera G.

Unit of Hospital Hygiene and Epidemiology, Azienda Ospedaliera - Universitaria Pisana, Pisa, Italy. b.casini@med.unipi.it

J Hosp Infect. 2008 Jun;69(2):141-7.

ABSTRACT: This paper describes the results of a five-year monitoring programme applied to the water distribution system of the University Hospital of Pisa (Italy). The purpose of the programme was to evaluate the efficacy of an integrated water safety plan in controlling Legionella spp. colonisation of the potable water system. The impact of the safety plan on the ecology of legionella in the water network was evaluated by studying the genetic variability and the chlorine susceptibility of the strains isolated prior to, and throughout, the application of continuous chlorine dioxide treatment. After 45 months of water hyperchlorination, Legionella spp. were still present but the positive supply points were reduced by 79.4%. The samples exceeding 10(3)cfu/L were reduced by 83.8% and the mean counts showed a decrease of 94.6%. The majority of the isolates belonged to Legionella pneumophila serogroup 1 (overall positivity rate: 161/423; 38%). Molecular typing was performed on 61 isolates (37.9% of the positive samples) selected on spatial and temporal criteria. This revealed the circulation and the persistence in the hospital environment of three prevalent types of L. pneumophila Wadsworth, demonstrating allelic and electrophoretic characteristic profiles and different chlorine susceptibility. Two of these, one predominant and pre-dating the sanitation regimen, and one other isolated after three years of water treatment, were chlorine tolerant. Despite the ineffectiveness of chlorine dioxide in eradicating L. pneumophila, the risk management plan adopted appeared to discourage further cases of nosocomial legionellosis.


The use of copper and silver in carbon point-of-use filters for the suppression of Legionella throughput in domestic water systems

Molloy SL, Ives R, Hoyt A, Taylor R, Rose JB.

Department of Biology, University of Hawaii at Hilo, Hilo, HI, USA. rosejo@msu.edu

J Appl Microbiol. 2008 Apr;104(4):998-1007.

ABSTRACT: AIMS: To evaluate throughput of seeded Legionella pneumophila bacteria in domestic point-of-use filters. METHODS AND RESULTS: The filters were challenged with tap water seeded with Leg. pneumophila. After multiple challenge events (4.25 x 10(11) CFU per filter), the levels of Legionella were lower in the effluent from the filter containing both copper and silver (mean 4.48 x 10(3) CFU ml(-1)) than in the effluent from the filter containing copper only (1.26 x 10(4) CFU ml(-1); P < 0.001). After a single challenge event of approx. 5 x 10(9) CFU L. pneumophila per filter, there was no significant difference between the levels of Legionella in the effluents from a carbon filter containing copper and a carbon filter with no metals (mean 6.87 x 10(2) and 6.89 x 10(2) CFU ml(-1), respectively; P = 0.985). CONCLUSIONS: Legionella was detected in filter effluent up to 6 weeks after being challenged, indicating that while filters may reduce the levels during an initial contamination event, the exposure is extended as the accumulated bacteria slough off over time. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has provided an understanding of the response of Legionella to the use of silver and copper in domestic point-of-use carbon filters.


Evaluation of the in-vitro cidal activity and toxicity of a novel peroxygen biocide: 2-butanone peroxide

García-de-Lomas J, Lerma M, Cebrián L, Esteban E, Giménez MJ, Aguilar L, Domínguez V, Randez JJ.

Microbiology Department, School of Medicine, University of Valencia, Valencia, Spain. jglomas@retemail.es

J Hosp Infect. 2008 Mar;68(3):248-54.

ABSTRACT: The monomer of 2-butanone peroxide is a novel peroxygen derivative with potential use as biocide in the hospital environment. The aim of this study was to test the biocidal activity of different concentrations of the compound against American Tissue Culture Collection strains from 11 different micro-organisms, including bacteria, mycobacteria, spores, fungi and virus, following the European Standard guidelines. Toxicity tests were also carried out following United States Environmental Protection Agency Standards. 2-Butanone peroxide exhibited biocidal activity at 0.12% against Legionella pneumophila, at 0.5% against Escherichia coli, Pseudomonas aeruginosa and Enterococcus hirae, and at 1% against Staphylococcus aureus after 5min contact at room temperature. Mycobactericidal activity was obtained at 0.5% after 60min contact at 20 degrees C, and sporicidal activity was obtained at 4% after 60min at 40 degrees C. Good fungicidal (against yeasts and moulds) and virucidal (adenovirus and poliovirus) activities were obtained at 0.5% after 60min contact. Toxicity assessment showed negative results in the acute dermal irritation test, acute eye irritation test and acute oral toxicity test. The skin sensitisation test was negative. The safety profile in the toxicity tests and the basic cidal activity against the strains tested suggest that 2-butanone peroxide in the control of hospital infections.


Effect of pipe corrosion scales on chlorine dioxide consumption in drinking water distribution systems

Zhang Z, Stout JE, Yu VL, Vidic R.

Department of Civil and Environmental Engineering, School of Engineering, University of Pittsburgh, 943 Benedum Hall, Pittsburgh, PA 15261, USA. Vidic@engr.pitt.edu

Water Res. 2008 Jan;42(1-2):129-36.

ABSTRACT: Previous studies showed that temperature and total organic carbon in drinking water would cause chlorine dioxide (ClO(2)) loss in a water distribution system and affect the efficiency of ClO(2) for Legionella control. However, among the various causes of ClO(2) loss in a drinking water distribution system, the loss of disinfectant due to the reaction with corrosion scales has not been studied in detail. In this study, the corrosion scales from a galvanized iron pipe and a copper pipe that have been in service for more than 10 years were characterized by energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The impact of these corrosion scale materials on ClO(2) decay was investigated in de-ionized water at 25 and 45 degrees C in a batch reactor with floating glass cover. ClO(2) decay was also investigated in a specially designed reactor made from the iron and copper pipes to obtain more realistic reaction rate data. Goethite (alpha-FeOOH) and magnetite (Fe(3)O(4)) were identified as the main components of iron corrosion scale. Cuprite (Cu(2)O) was identified as the major component of copper corrosion scale. The reaction rate of ClO(2) with both iron and copper oxides followed a first-order kinetics. First-order decay rate constants for ClO(2) reactions with iron corrosion scales obtained from the used service pipe and in the iron pipe reactor itself ranged from 0.025 to 0.083min (-1). The decay rate constant for ClO(2) with Cu(2)O powder and in the copper pipe reactor was much smaller and it ranged from 0.0052 to 0.0062min(-1). Based on these results, it can be concluded that the corrosion scale will cause much more significant ClO(2) loss in corroded iron pipes of the distribution system than the total organic carbon that may be present in finished water.


Antibacterial activities of plant essential oils against Legionella pneumophila

Chang CW, Chang WL, Chang ST, Cheng SS.

Institute of Environmental Health, College of Public Health, National Taiwan University, Taipei 100, Taiwan, Republic of China. chingwenchang@ntu.edu.tw

Water Res. 2008 Jan;42(1-2):278-86.

ABSTRACT: The objective of this study was to determine the antimicrobial activity of essential oils (EOs) extracted from Cinnamomum osmophloeum leaves and different tissues of Cryptomeria japonica against pathogenic Legionella pneumophila at 42 degrees C. Ten kinds of EOs were extracted by water distillation and their chemical constituents were quantified by gas chromatography-mass spectroscopy (GC-MS). The results showed that cinnamon leaf EO possessed stronger anti-L. pneumophila activity than C. japonica EO. In particular, the highest bactericidal effect was noted in contact with C. osmophloeum leaf EO of cinnamaldehyde type (characterized by its major constituent of cinnamaldehyde accounting for 91.3% of EO), regardless of contacted cell concentration (2 and 4logCFUml(-1)) or exposure time (10 and 60min). Cinnamaldehyde is responsible for anti-L. pneumophila activity based on the results of antimicrobial testing and statistical analysis. Stepwise regression analyses show that EO concentration is the most significant factor affecting the bioactivity of EO. It is concluded that C. osmophloeum leaf oil of cinnamaldehyde type and its major constituent, cinnamaldehyde, possess strong anti-L. pneumophila activities, and have the great potential to be used as an antibacterial agent to control legionellosis associated with hot tubs and spa facilities widely used in homes and resorts.


Thermal disinfection of hotels, hospitals, and athletic venues hot water distribution systems contaminated by Legionella species

Mouchtouri V, Velonakis E, Hadjichristodoulou C.

Department of Hygiene and Epidemiology, Faculty of Medicine, University of Thessaly, Larissa, Greece.

Am J Infect Control. 2007 Nov;35(9):623-7.

ABSTRACT: Legionella spp. (>/=500 cfu liter(-1)) were detected in 92 of 497 water distribution systems (WDS) examined. Thermal disinfection was applied at 33 WDS. After the first and second application of the disinfection procedure, 15 (45.4%) and 3 (9%) positive for remedial actions WDS were found, respectively. Legionella pneumophila was more resistant to thermal disinfection than Legionella non-pneumophila spp. (relative risk [RR] = 5.4, 95% confidence intervals [CI] = 1-35). WDS of hotels with oil heater were more easily disinfected than those with electrical or solar heater (RR = 0.4 95% CI = 0.2-0.8). Thermal disinfection seems not to be efficient enough to eliminate legionellae, unless repeatedly applied and in combination with extended heat flushing, and faucets chlorine disinfection.


Is copper-silver ionisation safe and effective in controlling legionella?

Cachafeiro SP, Naveira IM, García IG.

Galician Agency for Health Technology Assessment, Spain.

J Hosp Infect. 2007 Nov;67(3):209-16.

ABSTRACT: Copper-silver ionisation is gaining popularity worldwide as a water disinfection method. We review the literature that supports the effectiveness and safety of the copper-silver ionisation pertaining to legionella control in water distribution systems. A search between January 1997 and January 2007 was conducted in relevant health databases: Medline, Embase, NHS CRD, Cochrane Library Plus, Web of Knowledge, IME (Spanish Medical Index) and IBECS (Health Sciences Bibliographic Index). Ten published studies were selected according to inclusion and exclusion criteria previously established; most of these were experimental. Legionella levels decrease with the application of any of the procedures used in these studies and the procedures can be combined to obtain better outcomes. No studies containing an economic evaluation were found. We conclude that copper-silver ionisation is an effective method to control legionella, bearing in mind that eradication cannot be achieved by any method in isolation. Maintaining high temperatures in the water system can maximise effectiveness of the method. Copper-silver appears to be safe, as long as ion levels are monitored and kept within international recommended levels. More studies with concurrent control group, long follow-up and economic evaluation are required to properly assess this procedure.


Inactivation of Legionella pneumophila and Pseudomonas aeruginosa: evaluation of the bactericidal ability of silver cations

Hwang MG, Katayama H, Ohgaki S.

Department of Urban Engineering, The University of Tokyo, 7-3-1 Hongo Bunkyo, Tokyo 113-8656, Japan.

Water Res. 2007 Oct;41(18):4097-104.

ABSTRACT: In this study, silver cations dissolved as silver nitrate at various concentrations were exposed to Legionella pneumophila, Pseudomonas aeruginosa, and Escherichia coli to quantitatively estimate the bactericidal ability of silver. Observed data were analyzed using a newly developed model (Cs x T) that introduced a specific amount of chemisorbed silver onto a bacterial cell (Cs), which represented the chemisorption properties of silver on the bacterial cell body. Silver cations were rapidly chemisorbed onto bacterial cells after injection into samples, and Cs values (initial concentration of silver was 0.1 mg Ag/l) were calculated as 1.810 x 10(-6) (L. pneumophila), 1.102 x 10(-6) (P. aeruginosa), and 1.638 x 10(-6) microg Ag/cell(i) (E. coli) after incubation for 8 h. During that time, the three tested bacteria were completely inactivated under the detection limit (>7.2 log reduction). Based on the calculated Cs values, bacterial tolerance against silver was estimated by using the equation (Cs x T) multiplying the Cs values with exposure time (T). The Cs x T values well represented the bactericidal abilities of silver against the tested bacteria. The demanded Cs x T values to accomplish a 1 log inactivation (90% reduction) of L. pneumophila, P. aeruginosa, and E. coli (the initial numbers of bacteria were 1.5 x 10(7) CFU/ml, approximately) were estimated as 2.44 x 10(-6), 0.63 x 10(-6), and 0.46 x 10(-6) microgh/cell(i) of silver. The values were significantly reduced to 1.54 x 10(-6), 0.31 x 10(-6), and 0.25 x 10(-6) microgh/cell(i), respectively, with simultaneous injection of silver and copper. This study shows the successful quantitative estimation of the bactericidal ability of silver by applying the newly developed model (Cs x T). Among the tested bacteria, L. pneumophila showed the strongest tolerance to exposure of the same concentration of silver.


Safety and efficacy of chlorine dioxide for Legionella control in a hospital water system

Zhang Z, McCann C, Stout JE, Piesczynski S, Hawks R, Vidic R, Yu VL.

Department of Civil and Environmental Engineering, School of Engineering, University of Pittsburgh, Pittsburgh, PA, USA. jes20@pitt.edu

Infect Control Hosp Epidemiol. 2007 Aug;28(8):1009-12.

ABSTRACT: In a 30-month prospective study, we evaluated the efficacy of chlorine dioxide to control Legionella organisms in a water distribution system of a hospital with 364 patient beds and 74 skilled nursing beds. The number of hot water specimens positive for Legionella organisms decreased from 12 (60%) of 20 to 2 (10%) of 20. An extended time (18 months) was needed to achieve a significant reduction in the rate of Legionella positivity among hot water specimens. At the time of writing, no cases of hospital-acquired Legionnaires disease have been detected at the hospital since the chlorine dioxide system was installed in January 2003. Use of chlorine dioxide was safe, based on Environmental Protection Agency limits regarding maximum concentrations of chlorine dioxide and chlorite.


Disconnecting central hot water and using electric showers to avoid colonization of the water system by Legionella pneumophila: an 11-year study

Oliveira MS, Maximino FR, Lobo RD, Gobara S, Sinto SI, Ianhez LE, Warschauer CL, Levin AS.

Department of Infection Control, Hospital das Clínicas, Faculdade de Medicina, University of São Paulo, São Paulo, Brazil.  gcih@hcnet.usp.br

J Hosp Infect. 2007 Aug;66(4):327-31.

ABSTRACT: Legionella spp. can be difficult to control in hospitals. The objective of this study was to describe an 11-year experience with the use of electric showers in the control of Legionella pneumophila. From June 1989 to March 1990 there was an outbreak of pneumonia caused by L. pneumophila in a 20-bed renal transplant unit in a university-associated tertiary-care hospital. Control measures included hyperchlorination, heating and flushing of the water system with limited results. In November 1993 the central hot water was disconnected and water for bathing was heated using electric showers. From January 1992 to June 1995 water was collected from showers and water faucets and cultured for L. pneumophila every two weeks. Surveillance cultures were then collected every month until May 1999. During this seven-year surveillance period, 1115 samples of water were cultured. Water cultures were positive on 24 of 429 occasions (without cases of legionellosis) during the pre-shower period (22 months). In the post-shower period (67 months) only one of 686 cultures was positive. Subsequently there have been no new cases of nosocomial pneumonia by L. pneumophila although surveillance continues. In conclusion, disconnecting the central hot water was effective in avoiding colonization of the water system by L. pneumophila. Heating was possible by using electric showers, which are effective, easy to maintain and cheap.



Effects of chlorination and heat disinfection on long-term starved Legionella pneumophila in warm water

Chang CW, Hwang YH, Cheng WY, Chang CP.

Institute of Environmental Health, College of Public Health, National Taiwan University, Taipei, Taiwan. cchang@ha.mc.ntu.edu.tw

J Appl Microbiol. 2007 Jun;102(6):1636-44. 

ABSTRACT: AIMS: To characterize the efficacy of widely accepted heat and chlorination on culturable and non-culturable Legionella pneumophila in starved and warm water. METHODS AND RESULTS: For L. pneumophila starved for 1 day (S1), heating at 60 degrees C or more for 30 min or chlorination at 0.5-20 mg l(-1) for 60 min, a loss of 6-8 log culturability was observed, whereas only 17-47% of cells had membrane damage. Non-culturability was also observed after heating or chlorinating the cells starved for 14 days (S14). The effect of heating on membrane deterioration was reduced for S14 cells while the chlorination effect remained. Legionella pneumophila entered a non-culturable phase after being starved for 33-40 days. The disinfection effects of both heating and chlorination on non-culturable N4 and N35 cells (which were collected on the fourth and the 35th days of the non-culturability phase respectively) decreased, indicating the development of disinfection resistance among non-culturable cells that had been subjected to starvation for 1-2 months. CONCLUSIONS: Heating and chlorination significantly reduce the culturability of starved L. pneumophila, and damage cell membrane to a much less extent. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows the ability of long-term starved L. pneumophila to resist against disinfection treatments, which has implications in terms of public health.


Hygienic safety of reusable tap water filters (Germlyser) with an operating time of 4 or 8 weeks in a haematological oncology transplantation unit

Daeschlein G, Krüger WH, Selepko C, Rochow M, Dölken G, Kramer A.

Institute for Hygiene and Environmental Medicine, Germany. daeschlein@uni-greifswald.de

BMC Infect Dis. 2007 May 23;7:45.

BACKGROUND: Microbial safe tap water is crucial for the safety of immunosuppressed patients. METHODS: To evaluate the suitability of new, reusable point-of-use filters (Germlyser, Aquafree GmbH, Hamburg, Germany), three variations of a reusable filter with the same filter principle but with different outlets (with and without silver) and inner surface coating of the filter encasements (with and without nano-crystalline silver) were tested. The filter efficacy was monitored over 1, 4 and 8 weeks operating time in a haematological oncology transplantation unit equipped with 18 water outlets (12 taps, 6 showers). RESULTS: The filtered water fulfilled the requirements of absence of pathogens over time. From 348 samples, 8 samples (2.3%) exceeded 100 cfu/ml (no sample > or = 500 cfu/ml). As no reprocessed filter exhibited 100% filter efficacy in the final quality control after each reprocessing, these contaminations could be explained by retrograde contamination during use. CONCLUSION: As a consequence of the study, the manufacturer recommends changing filters after 4 weeks in high risk areas and after 8 weeks in moderate infectious risk areas, together with routine weekly alcohol-based surface disinfection and additionally in case of visible contamination. The filter efficacy of the 3 filters types did not differ significantly regarding total bacterial counts. Manual reprocessing proved to be insufficient. Using a validated reprocessing in a washer/disinfector with alkaline, acid treatment and thermic disinfection, the filters were effectively reprocessable and now provide tap water meeting the German drinking water regulations as well as the WHO guidelines, including absence of pathogens.


Studies on the efficacy of Chloramine T trihydrate (N-chloro-p-toluene sulfonamide) against planktonic and sessile populations of different Legionella pneumophila strains

Ozlem Sanli-Yurudu N, Kimiran-Erdem A, Cotuk A.

Department of Biology, Faculty of Science, Istanbul University, 34418 Istanbul, Turkey. ozlem_sanli@yahoo.com

Int J Hyg Environ Health. 2007 Mar;210(2):147-53.

ABSTRACT: Effectiveness of Chloramine T trihydrate (N-chloro-p-toluene sulfonamide) on both planktonic and sessile populations of different Legionella pneumophila strains was assessed. Although Chloramine T is a recommended commercial formulation for disinfecting cooling towers, there is a lack of published data about the efficacy of this compound against both planktonic and sessile populations of L. pneumophila. Planktonic L. pneumophila strains were suspended in tap water and sessile L. pneumophila strains were grown on stainless steel which is used in the construction of cooling towers, followed by exposure to the biocide. The sensitivity of both planktonic and sessile populations of L. pneumophila strains was different. The biocide was found effective below recommended dosages (0.1-0.3%) against planktonic populations of L. pneumophila, whereas it was determined that higher dosages than those recommended were required for sessile populations of L. pneumophila. The results indicated that studying only the planktonic populations of L. pneumophila for biocide tests might not be sufficient to provide information about the optimum dosage and contact time. Therefore, efficacy has to be tested on both planktonic and sessile bacteria.


Prospective monitoring study: isolating Legionella pneumophila in a hospital water system located in the obstetrics and gynecology ward after eradication of Legionella anisa and reconstruction of shower units

Koide M, Owan T, Nakasone C, Yamamoto N, Haranaga S, Higa F, Tateyama M, Yamane N, Fujita J.

Department of Medicine and Therapeutics, Control and Prevention of Infectious Diseases, Faculty of Medicine, Univeristy of the Ryukyus, Okinawa 903-0215, Japan. koide-mi@med.u-ryukyu.ac.jp

Jpn J Infect Dis. 2007 Feb;60(1):5-9. 

ABSTRACT: We previously reported on the sporadic contamination by Legionella anisa of shower units and sink taps at Ryukyu University Hospital. Starting in July 2003, the neonatal area underwent an 8-month reconstruction, and in March 2005, the boiler system was replaced. We therefore examined shower water and tap water for the presence of Legionella just after replacement of the boiler system. In 3 of the 8 water samples collected from the remodeled area, we isolated Legionella pneumophila serogroup 1 and L. anisa. Moreover, L. pneumophila serogroup 1 was isolated in 4 of the 5 water samples gathered from the unreconstructed area of the same floor. Random amplified polymorphic DNA analysis suggested that a single clone of L. pneumophila might exist throughout the floors of the water distribution system. We replaced the shower units at the Legionella-positive site, and began flushing the sink-faucets with water heated to 55N for at least 1 h every morning. As a result, Legionella was not subsequently isolated in water samples. In this prospective study, we identified a central contamination by L. pneumophila serogroup 1 and showed that flushing with hot tap water was effective to counter this situation.


Disinfection of Legionella pneumophila by photocatalytic oxidation

Cheng YW, Chan RC, Wong PK.

Department of Biology, The Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR, China. pkwong@cuhk.edu.hk

Water Res. 2007 Feb;41(4):842-52.

ABSTRACT: Photocatalytic oxidation (PCO) was proven to be efficacious in the inactivation of Legionella pneumophila serogroup 1 Strains 977, 1009, 1014 and ATCC 33153. The local (Strains 997, 1009 and 1014) and ATCC (Strain 33153) strains showed sensitivity differences towards PCO. The inactivation mechanisms of PCO were investigated by transmission and scanning electron microscopy by which PCO was found to disintegrate the cells eventually. Before the disintegration, there was lipid peroxidation of outer and cytoplasmic membrane causing holes formation and leading to the entry of OH into the cells to oxidize the intracellular components. Fatty acid profile analysis found that the amount of saturated, 16-carbon branched-chain fatty acid, which is predominant in Legionella, decreased in the surviving populations from PCO. A relationship between the amount of this fatty acid and the PCO sensitivity of the tested strains was also observed. Mineralization of cells by PCO was proven by total organic carbon analysis.


Hospital-acquired legionnaires disease in a university hospital: impact of the copper-silver ionization system

Mòdol J, Sabrià M, Reynaga E, Pedro-Botet ML, Sopena N, Tudela P, Casas I, Rey-Joly C.

Section of Infectious Diseases, Department of Medicine, Hospital Universitari Germans Trias i Pujol, Universitat Autonoma de Barcelona, Barcelona, 08916, Spain. jmmodol.germanstrias@gencat.net

Clin Infect Dis. 2007 Jan 15;44(2):263-5.

ABSTRACT: We evaluated the impact of the copper-silver ionization system in a hospital where hyperendemic nosocomial legionellosis and was present and all previous disinfection measures had failed. After implementation of the copper-silver ionization system, environmental colonization with Legionella species decreased significantly, and the incidence of nosocomial legionellosis decreased dramatically, from 2.45 to 0.18 cases per 1000 patient discharges.


Effect of intracellular resuscitation of Legionella pneumophila in Acanthamoeba polyphage cells on the antimicrobial properties of silver and copper

Hwang MG, Katayama H, Ohgaki S.

Department of Urban Engineering, The University of Tokyo, 3-1-7 Hongo Bunkyo, Tokyo 133-8656, Japan. mghwang@env.t.u-tokyo.ac.jp

Environ Sci Technol. 2006 Dec 1;40(23):7434-9.

ABSTRACT: The property of Legionella pneumophila entering into a viable but noncultivable (VBNC) state under drinking water conditions (50 mL, pH 7.0, and 25 degrees C) and the intracellular resuscitation in Acanthamoeba polyphage cells were investigated. Then, the survival profiles of L. pneumophila residing in the planktonic phase and the endosymbiosis phase against antimicrobial silver and copper reagents were differentially compared with the case of Pseudomonas aeruginosa. The number of L. pneumophila in a cultivable state was rapidly reduced to below the detection limit (5.0 log reduction) within 30 days of incubation in synthetic drinking water, while the number of L. pneumophila in a viable state varied in only 0.1 log reduction during the same period, and the levels were sustained constantly for 190 days; in contrast, P. aeruginosa multiplied even in drinking water and continuously maintained its cultivability and viabilityfor 190 days. Distinctively, the numbers of E. coli in both cultivable and viable states were simultaneously diminished as 3.0 log and 1.6 log reduction. The cultivability of L. pneumophila in the VBNC state was recovered and started to multiply after coincubation with A. polyphage in the same environment (initial population of inoculated amoeba was adjusted as 1.0 x 10(5) amoeba/ mL), and P. aeruginosa also multiplied in amoeba cells. Finally, the populations of L. pneumophila in the planktonic phase after 10 days coincubation were detected at 1.7 x 10(7) CFU/mL, and this population was considered to have originated from the release of bacteria residing inside amoeba caused by the destruction of amoeba cells. Bacteria in the planktonic phase that were exposed to silver and copper were completely inactivated (more than 7 log reduction) within 30 min, while bacteria in the endosymbiosis phase showed much higher resistance against the exposure to the same concentrations of silver and copper. L. pneumophila and P. aeruginosa in A. polyphage cells survived to levels of 5.6 x 10(1) and 1.1 x 10(1) CFU/mL at the silver exposure (0.1 mgAg/L) and 7.3 x 10(3) and 6.1 x 10(4) CFU/ mL at the copper exposure (1.0 mgCu/L), respectively, after 7 days.


Antibacterial effects of chitosan solution against Legionella pneumophila, Escherichia coli, and Staphylococcus aureus

Fujimoto T, Tsuchiya Y, Terao M, Nakamura K, Yamamoto M.

Department of Community Preventive Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata 951-8510, Japan.


Int J Food Microbiol. 2006 Nov 1;112(2):96-101.

ABSTRACT: Chitosan has been shown to have antibacterial activities on the growth of a wide variety of bacteria. Chitosan solution has been sold commercially for use as an antibacterial agent. Chitosan solution contains not only chitosan but also organic acids as solvents and desalted Japan Sea Proper Water (dJSPW). We aimed to clarify whether chitosan solution has antibacterial activity against bacteria invading bath water, and then to explore the causative factor among these ingredients. The antibacterial activity of full-strength chitosan solution and of 10(2)- and 10(4)-fold chitosan solution diluted with purified water was studied against Legionella pneumophila serogroups 1 (L. pneumophila SG1) and 6 (L. pneumophila SG6), Escherichia coli (E. coli), and Staphylococcus aureus (S. aureus) for 7 days at 37 degrees C. To clarify the causative factor in the antibacterial activity against E. coli, the antibacterial activities of the full-strength and diluted chitosan solutions for 24 h were examined. L. pneumophila SG1 and SG6, and E. coli could not survive in the chitosan solution or in the 10(2)-fold dilute solution for over a day at 37 degrees C. The cells of S. aureus were found to have decreased more than 2.46 log cfu/ml after 1 day of incubation, not only in the chitosan solutions, but also in phosphate buffer solution as a control. No inhibitory effect of dJSPW on the growth of the bacteria was observed. The antibacterial activity of the chitosan solution was lower compared with those of the organic acids solutions, and it increased with decreasing pH value. We observed the antibacterial activity of chitosan solution against L. pneumophila SG1 and SG6, and E. coli, suggesting it may be due to the decreased pH value derived from organic acids rather than from chitosan itself or dJSPW.


Control of Legionella pneumophila contamination in a respiratory hydrotherapy system with sulfurous spa water

Leoni E, Sacchetti R, Zanetti F, Legnani PP.

Department of Medicine and Public Health, Division of Hygiene, University of Bologna, Bologna, Italy.

Infect Control Hosp Epidemiol. 2006 Jul;27(7):716-21.

OBJECTIVE: To evaluate the effectiveness of different disinfection treatments in a spa water system contaminated by Legionella pneumophila and associated with a case of Legionella pneumonia. DESIGN: During an 18-month period, the spa water was analyzed by taking samples from the well, the recirculation line, and the final distribution devices (nebulizers and nasal irrigators). Various attempts were made to eradicate Legionella organisms by chemical and thermal shock. The final protocol consisted of heat shock treatment at 70 degrees C-75 degrees C for 3 hours, 2 nights per week, followed by a lowering of the water temperature to 30 deg C+/-1 deg C for use in the plant. In addition, 3 times a week superheated steam (at a pressure of 1 atmosphere) was introduced for 1 hour into the nebulization machines. SETTING: A spa at which sulfurous water was used for hydrotherapy by means of aerosol and nasal irrigation. PATIENT: A 74-year-old woman with legionnaires disease. RESULTS: After the case of infection occurred, L. pneumophila was isolated from the recirculation line at a concentration of 400,000 cfu/L and from the nebulizers and nasal irrigators at levels ranging from 3,300 to 1,800,000 cfu/L. The colonizing organisms consisted of a mixture of L. pneumophila serogroup 1 (12%) and serogroup 5 (88%). The shock treatment with chlorine dioxide and peracetic acid resulted in the eradication of Legionella organisms from the recirculation line but not from the water generated from the final distribution devices. After the restructuring of the plant and the application of thermal shock protocol, an evaluation after 12 months revealed no evidence of Legionella contamination. CONCLUSION: To prevent Legionella colonization, disinfection treatment is effective if associated with carefully selected materials, good circuit design, and good maintenance practices.



Clinical and environmental distribution of Legionella pneumophila in a university hospital in Italy: efficacy of ultraviolet disinfection

Triassi M, Di Popolo A, D'Alcala GR, Albanese Z, Cuccurullo S, Montegrosso S, Crispino M, Borella P, Zarrilli R.

Dipartimento di Scienze Mediche Preventive, Sezione di Igiene, Universita di Napoli 'Federico II', Napoli, Italy.

J Hosp Infect. 2006 Apr;62(4):494-501.

ABSTRACT: The molecular epidemiology of Legionella pneumophila in the 'V. Monaldi' University Hospital was studied. Seven cases of nosocomial Legionnaires' disease were diagnosed between 1999 and 2003. Two clinical legionella strains obtained from two patients in the adult cardiac surgery unit (CSU) and 30 environmental legionella strains from the paediatric and adult CSUs, neonatal intensive care unit (NICU) and the cardiorespiratory intensive care unit (CR-ICU) were serotyped and genotyped. L. pneumophila serogroup 1/Philadelphia with an identical pulsed-field gel electrophoresis (PFGE) profile A was isolated from two patients in the adult CSU, and from three and one water samples taken in the adult CSU and the paediatric CSU, respectively, from 2001 to 2002. Furthermore, L. pneumophila serogroup 3 with an identical PFGE profile B was identified in 20 environmental strains from all wards, L. pneumophila serogroup 3 with PFGE profile C was identified in a single environmental strain from the CR-ICU, and non-pneumophila Legionella with identical PFGE profile D was identified in five environmental strains from the adult CSU, paediatric CSU and NICU. Ultraviolet irradiation was effective in disinfection of the hospital water supplies in the adult and paediatric CSUs contaminated by L. pneumophila clone associated with nosocomial Legionnaires' disease. In conclusion, these data demonstrate that two cases of nosocomial legionellosis were caused by the persistence of a single clone of L. pneumophila serogroup 1/Philadelphia in the hospital environment, and that disinfection by ultraviolet irradiation may represent an effective measure to prevent nosocomial Legionnaires' disease.


Disinfection of Legionella pneumophila by ultrasonic treatment with TiO(2)

Farshbaf Dadjour M, Ogino C, Matsumura S, Nakamura S, Shimizu N.

Division of Biological Measurement and Applications, Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa, 920-1192, Japan.

Water Res. 2006 Mar;40(6):1137-42.

ABSTRACT: An ultrasonic treatment system, using a TiO(2) photocatalyst, was used to disinfect Legionella pneumophila. A kinetic study of the process indicates that TiO(2) significantly improves the disinfection process. The concentrations of viable cells were reduced to 6% of the initial concentrations in the presence of 0.2g/ml TiO(2) after a 30min of treatment period, while only an 18% reduction was observed in the absence of TiO(2). The potency of the disinfection could be enhanced, to some extent, by increasing the amount of TiO(2) used. Cell concentrations were decreased by an order of 3 within 30min of treatment in the presence of 1.0g/ml TiO(2). The disinfection power in the presence of TiO(2) versus Al(2)O(3) was also compared and the findings showed that TiO(2) induced a higher cell killing. No significant effect of initial cell concentration on the disinfection was found in the range of 10(2)-10(7)CFU/ml after a 30min of treatment period. The mechanism of cell killing was investigated by examining the effects of OH radical scavengers such as ascorbic acid, histidine and glutathione. The disinfection power was reduced in samples that contained these radical scavengers, thus indicating the importance of OH radicals.


Abbreviated duration of superheat-and-flush and disinfection of taps for Legionella disinfection: lessons learned from failure

Chen YS, Liu YC, Lee SS, Tsai HC, Wann SR, Kao CH, Chang CL, Huang WK, Huang TS, Chao HL, Li CH, Ke CM, Lin YS.

Section of Infectious Diseases of the Department of Internal Medicine, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan, Republic of China.

Am J Infect Control. 2005 Dec;33(10):606-10.

ABSTRACT: One medical center in southern Taiwan faced an outbreak of nosocomial Legionnaires' disease; a total of 81 suspected cases were detected during an 8-month period. Baseline environmental surveillance showed that 80% of the distal sites in intensive care units (ICUs) were positive for Legionella pneumophila. Superheat-and-flush was selected for hospital water supply disinfection because it required no special equipment, and it can be initiated expeditiously. We conducted 2 episodes of superheat-and-flush based on the published recommendations from the Department of Health, Taiwan; US Centers for Disease Control and Prevention; and American Society of Heating, Refrigerating, and Air-Conditioning Engineers. Both flushes failed to control colonization of Legionella in the hospital water supply. The rate of distal sites positive for Legionella in wards and ICUs was 14% and 66%, respectively, 10 days after the second flush. The effect of replacement of faucets and showerheads in ICUs appeared to be insignificant in colonization of Legionella. The application of superheat-and-flush for flush duration of 5 minutes was ineffective. Superheat-and-flush may not be economic for a large medical center because it could be costly and labor intensive.


Disinfection by-products and microbial contamination in the treatment of pool water with granular activated carbon

Uhl W, Hartmann C.

University of Duisburg-Essen, Institute for Energy and Environmental Process Engineering (EUT), Water Technology Department, Germany.

Water Sci Technol.2005;52(8):71-6.

ABSTRACT: For swimming pools, it is generally agreed that free chlorine levels have to be maintained to guarantee adequate disinfection. Recommended free chlorine levels can vary between 0.3 and 0.6 mg/L in Germany and up to 3 mg/L in other countries. Bathers introduce considerable amounts of organic matter, mainly in the form of such as urine and sweat, into the pool water. As a consequence, disinfection byproducts (DBPs) are formed. Regulations in Germany recommend levels of combined chlorine of less than 0.2 mg/L and levels of trihalomethanes (THMs) of less than 20 microg/L. Haloacetic acids (HAAs), haloacetonitriles (HANs), chloropicrin and chloral hydrate are also detected in considerable amounts. However, these compounds are not regulated yet. Swimming pool staff and swimmers, especially athletes, are primarily exposed to these byproducts by inhalation and/or dermal uptake. In Germany, new regulations for swimming pool water treatment generally require the use of activated carbon. In this project, three different types of granular activated carbon (GAC) (one standard GAC, two catalytic GACs) are compared for their long time behaviour in pool water treatment. In a pilot plant operated with real swimming pool water, production and removal of disinfection byproducts (THMs, HAAs, AOXs), of biodegradable substances (AOC), of bacteria (Pseudomonas aeruginosa, Legionella, coliforms, HPC) as well as the removal of chlorine and chloramines are monitored as function of GAC bed depth. Combined chlorine penetrates deeper in the filter bed than free chlorine does. However, both, free and combined chlorine removal efficiencies decrease over the time of filter operation. The decreases of removal efficiencies are also observed for parameters such as dissolved organic carbon, spectral absorption coefficient, adsorbable organic carbon and most of the disinfection byproducts. However, THMs, especially chloroform are produced in the filter bed. The GAC beds were contaminated microbially, especially with P. aeruginosa. The contamination was not removable by backwashing with chlorine concentrations up to 2 mg/l free chlorine.


Introduction of Monochloramine into a Municipal Water System: Impact on Colonization of Buildings by Legionella spp

Moore MR, Pryor M, Fields B, Lucas C, Phelan M, Besser RE.

Centers for Disease Control and Prevention, 1600 Clifton Road, MS C-23, Atlanta, GA 30333.

Appl Environ Microbiol. 2006 Jan;72(1):378-83.

ABSTRACT: Legionnaires' disease (LD) outbreaks are often traced to colonized potable water systems. We collected water samples from potable water systems of 96 buildings in Pinellas County, Florida, between January and April 2002, during a time when chlorine was the primary residual disinfectant, and from the same buildings between June and September 2002, immediately after monochloramine was introduced into the municipal water system. Samples were cultured for legionellae and amoebae using standard methods. We determined predictors of Legionella colonization of individual buildings and of individual sampling sites. During the chlorine phase, 19 (19.8%) buildings were colonized with legionellae in at least one sampling site. During the monochloramine phase, six (6.2%) buildings were colonized. In the chlorine phase, predictors of Legionella colonization included water source (source B compared to all others, adjusted odds ratio [aOR], 6.7; 95% confidence interval [CI], 2.0 to 23) and the presence of a system with continuously circulating hot water (aOR, 9.8; 95% CI, 1.9 to 51). In the monochloramine phase, there were no predictors of individual building colonization, although we observed a trend toward greater effectiveness of monochloramine in hotels and single-family homes than in county government buildings. The presence of amoebae predicted Legionella colonization at individual sampling sites in both phases (OR ranged from 15 to 46, depending on the phase and sampling site). The routine introduction of monochloramine into a municipal drinking water system appears to have reduced colonization by Legionella spp. in buildings served by the system. Monochloramine may hold promise as community-wide intervention for the prevention of LD.


Resistance of Legionella to disinfection in hot water distribution systems

Saby S, Vidal A, Suty H.

Veolia Environnement, Anjou Recherche, France.

Water Sci Technol. 2005;52(8):15-28.

ABSTRACT: The efficiency of various disinfection treatments against Legionella was tested on a hot water distribution system (HWDS) pilot unit. The results demonstrated clearly that most Legionella in the networks were fixed in the biofilm at the surface of the pipe (more than 98% for each loop). Chemical treatments (continuous chlorination, hyperchlorination, hydrogen peroxide and peracetic acid mixing) commonly used for the eradication of Legionella in hot water distribution networks appeared to be inadequate for eradicating the bacteria in the biofilm. Unfortunately, the biofilm contained most of the pathogens in an HWDS whereas legislation is only restricted to the Legionella concentration in the water phase. Thermal treatment appeared to be efficient to disinfect most of the biofilm but seemed to promote the biofilm re-growth as well. It was then concluded that the best solution to prevent Legionella contamination in hot water distribution systems would be to have perfect control of the temperature in the networks (temperature > 55 degrees C at all points). Nevertheless, in many cases it is difficult to have such control, so during the time necessary to modify networks, the best solution to control Legionella proliferation appears to be to apply a treatment shock (thermal or chlorination as a function of pipe characteristics). These treatments must be followed by a continuous chlorination that is totally controlled and equipped with alarm systems. This study demonstrates that biofilm sampling devices must be installed in hot water distribution systems to anticipate Legionella contamination and correctly determine the efficiency of the treatments.


Effectiveness of installing an antibacterial filter at water taps to prevent Legionella infections

Salvatorelli G, Medici S, Finzi G, De Lorenzi S, Quarti C.

Department of Biology, University of Ferrara, Italy.

J Hosp Infect. 2005 Nov;61(3):270-1.



Possible phosphate interference with copper-silver ionization for Legionella control

Lin YE, Vidic RD.

Graduate Institute of Environmental Education, National Kaohsiung Normal University, Kaohsiung Hsien, Taiwan, ROC.

J Hosp Infect. 2005 Oct 6; [Epub ahead of print]



Monitoring and control of opportunistic bacteria in a spa water used for aerosol hydrotherapy [Article in Italian]

Leoni E, Zanetti F, Cristino S, Legnani PP.

Dipartimento di Medicina e Sanità Pubblica, Sezione di Igiene, Università degli Studi di Bologna.

Ann Ig. 2005 Sep-Oct;17(5):377-84.

ABSTRACT: A bicarbonate-sulphate-calcic water of a therapeutic spa was monitored for the presence of Legionella, Pseudomonas and Mycobacteria. The water was analysed by taking samples from the well, the feed tank and from the final aerosol generating devices of two different water lines, the former at 21-23 degrees, the second at 36-38 degrees. The bacteria in question were always absent from the well. Legionellae were found in the water of aerosol equipment: Legionella micdadei was isolated from 75% of samples, L. bozemanii from 75% and 50% (respectively 36-38 degrees and 21-22 degrees water lines) and other species of environmental Legionellae from 25% of samples. The water of aerosol equipment presented high total bacterial counts (10(3)-10(4) cfu/ml) and exspecially high concentrations of Pseudomonadaceae (10(2)-10(3) cfu/100 ml). These bacteria, unlike the Legionellae, were also isolated from the feed tank at mean concentrations of about 10(2) cfu/100 ml. Mycobacteria were found in 75 and 50% of samples collected from final devices, respectively from the heated and not heated water lines. The isolates were M. gordonae (85% of isolates) and M. fortuitum (15%), but at concentrations very low. Both treatments with sodium hypochlorite (20 ppm of residual chlorine) and peracetic acid (20 ppm) resulted in the reduction of total bacterial counts and elimination of Pseudomonas from the water in the tank, but not in elimination of Pseudomonas and Legionellae from the nebulizers. The disinfectants were evidently not able to efficiently reach all the points where Pseudomonas and Legionella had settled and grown. In order to obtain total abatement it was necessary to carry out a radical restructuring of the plant, involving the replacement of the old nebulizer benches with new aerosol equipment that could be subjected to a new system of programmed thermal shock.


Point-of-care controls for nosocomial legionellosis combined with chlorine dioxide potable water decontamination: a two-year survey at a Welsh teaching hospital

Hosein IK, Hill DW, Tan TY, Butchart EG, Wilson K, Finlay G, Burge S, Ribeiro CD.

Infection Prevention and Control Department, Cardiff and Vale NHS Trust, University Hospital of Wales, Heath Park, Cardiff CF14 4XW, Wales, UK.

J Hosp Infect. 2005 Oct;61(2):100-6.

ABSTRACT: This study reports a two-year programme of attempted eradication of Legionella colonization in the potable water supply of a 1000-bed tertiary care teaching hospital in Wales. There was a simultaneous, point-of-care, sterile-water-only policy for all intensive care units (ICU) and bone marrow and renal transplant units in order to prevent acquisition of nosocomial Legionnaires' disease. The programme was initiated following a case of nosocomial pneumonia caused by Legionella pneumophila serogroup 1-Bellingham-like genotype A on the cardiac ICU. The case occurred 14 days after mitral and aortic valve replacement surgery. Clinical and epidemiological investigations implicated aspiration of hospital potable water as the mechanism of infection. Despite interventions with chlorine dioxide costing over 25000 UK pounds per annum, Legionella has remained persistently present in significant numbers (up to 20000 colony forming units/L) and with little reduction in the number of positive sites. Two further cases of nosocomial disease occurred over the following two-year period; in one case, aspiration of tap water was implicated again, and in the other case, instillation of contaminated water into the right main bronchus via a misplaced nasogastric tube was implicated. These cases arose because of inadvertent non-compliance with the sterile-water-only policy in high-risk locations. Enhanced clinical surveillance over the same two-year period detected no other cases of nosocomial disease. This study suggests that attempts at eradication of Legionella spp. from complex water systems may not be a cost-effective measure for prevention of nosocomial infections, and to the best of our knowledge is the first study from the UK to suggest that the introduction of a sterile-water-only policy for ICUs and other high-risk units may be a more cost-effective approach.


Evaluation of the effectiveness of the Pastormaster method for disinfection of legionella in a hospital water distribution system

Peiro Callizo EF, Sierra JD, Pombo JM, Baquedano CE, Huerta BP.

Department of Health Care, Osakidetza-Basque Health Service, Spain.

J Hosp Infect. 2005 Jun;60(2):150-8.

ABSTRACT: The Pastormaster method consists of heating the water of hospital distribution systems at a specific point to a sufficient temperature for a minimum amount of time to eradicate legionella. The object of this study was to evaluate the effectiveness of the Pastormaster method for legionella disinfection in a hospital environment. A two-phase procedure was performed: hydraulic optimization of the water supply circuit, and implementation of the Pastormaster method. Water samples were taken at 10 representative points in the hospital hot-water system and cultured microbiologically. Other physical and chemical measurements were also determined. Implementation of the Pastormaster method and correction of the deficiencies identified during a hydraulic system audit confirmed the absence of legionella in the hospital water distribution system. The combination of implementation of the Pastormaster method and conduction of a hydraulic audit designed to identify and remedy any possible problems in water circulation is effective in minimizing the risk of legionella contamination in hospital water distribution systems.


Peracetic acid in the disinfection of a hospital water system contaminated with Legionella species

Ditommaso S, Biasin C, Giacomuzzi M, Zotti CM, Cavanna A, Ruggenini Moiraghi A.

Dipartimento di Sanitta Pubblica e di Microbiologia, Universita degli Studi di Torino, Torino, Italy.

Infect Control Hosp Epidemiol. 2005 May;26(5):490-3.

ABSTRACT: OBJECTIVE: To assess the efficacy of an alternative disinfection method for hospital water distribution systems contaminated with Legionella. METHODS: Disinfection with peracetic acid was performed in a small hospital contaminated with L. pneumophila serotype 1. The disinfectant was used at concentrations of 50 ppm (first three surveillance phases) and 1,000 ppm (fourth surveillance phase) for 30 minutes. RESULTS: Environmental monitoring revealed that disinfection was maintained 1 week after treatment; however, levels of recontamination surpassing baseline values were detected after approximately 1 month. Comparison of water temperatures measured at the distal outlets showed a statistically significant association between temperature and bacterial load. The circulating water temperature was found to be lower in the two wards farthest away from the hot water production plant than in other wards. It was thought that the lower water temperature in the two wards promoted the bacterial growth even after disinfection. CONCLUSION: Peracetic acid may be useful in emergency situations, but does not provide definitive protection even if used monthly.


Water disinfection with ozone, copper and silver ions, and temperature increase to control Legionella: seven years of experience in a university teaching hospital

Blanc DS, Carrara P, Zanetti G, Francioli P.

Division of Hospital Preventive Medicine, University Hospital of Lausanne (CHUV), Lausanne, Switzerland.

J Hosp Infect. 2005 May;60(1):69-72.

ABSTRACT: The efficacy of ozonation, copper-silver ionization and increased temperature in controlling Legionella spp. in the hot water distribution networks of a university hospital was evaluated. Two separate water distribution networks were studied; network 1 which supplies the surgical intensive care units, and network 2 which supplies the medical intensive care units and the emergency room. Network 1 has been disinfected by ozonation since 1995, and network 2 has been disinfected by ionisation since 1999. The hot water temperature was increased from 50 to 65 degrees C in 1998 and 2000 in networks 1 and 2, respectively. Water samples and swabs of the water outlets were cultured for Legionella spp. between four and six times each year, providing data before and after implementation of the disinfection procedures. There was no significant difference in the proportion of samples positive for Legionella spp. after ozonation in network 1 or after ionization in network 2. In both networks, there was a significant reduction in legionella isolates after increasing the hot water temperature to 65 degrees C. Maintaining the hot water temperature above 50 degrees C throughout both networks proved to be the most effective control measure in our hospital.


Persistent Legionella pneumophila colonization of a hospital water supply: efficacy of control methods and a molecular epidemiological analysis

Perola O, Kauppinen J, Kusnetsov J, Karkkainen UM, Luck PC, Katila ML.

Department of Clinical Microbiology, Kuopio University Hospital, Kuopio, Finland.

APMIS. 2005 Jan;113(1):45-53.

ABSTRACT: After a nosocomial outbreak caused by Legionella pneumophila serogroup 5, the hospital water distribution system, which was found to be colonized by L. pneumophila serogroups 5 and 6, was decontaminated by the superheat and flush method and by installing an additional heat-shock unit in one of the hot water circuits. This unit exposed the recirculated water to a temperature of 80 degrees C. The efficacy of the decontamination measures was evaluated by monitoring the temperatures and legionella concentrations at different parts of the hot water distribution system. The genetic diversity of the colonizing legionella flora was examined using two genotyping methods: amplified fragment length polymorphism analysis (AFLP) and random amplified polymorphic DNA (RAPD) analysis. Selected serogroup 6 strains were also analyzed by sequence-based typing (SBT). The results indicated that long-term eradication of serogroup 5 strains was never achieved. Only one serogroup 6 strain was never isolated after the superheat and flush. In all, according to genetic fingerprints, the diversity of Legionella strains in a hospital water system remains stable over the years regardless of the use of recommended disinfection procedures.


Amoebae in domestic water systems: resistance to disinfection treatments and implication in Legionella persistence

Thomas V, Bouchez T, Nicolas V, Robert S, Loret JF, Levi Y.

Department of Public Health-Environment, School of Pharmacy , University of Paris , Chatenay-Malabry Cedex, France . vthomas@hospvd.ch

J Appl Microbiol. 2004;97(5):950-63

ABSTRACT: AIMS: Monitoring of microbial changes during and after application of various disinfection treatments in a model domestic water system. METHODS AND RESULTS: A pilot-scale domestic water system consisting of seven galvanized steel re-circulation loops and copper dead legs was constructed. Culture techniques, confocal laser scanning microscopy after fluorescent in situ hybridization and viability staining with the BacLight LIVE/DEAD kit were used for planktonic and biofilm flora monitoring. Before starting the treatments, the system was highly contaminated with Legionella pneumophila and biofilm populations mainly consisted of beta-proteobacteria. In the water and the biofilm of the loops, continuous application of chlorine dioxide (0.5 mg l(-1)), or chlorine (2.5 mg l(-1)) were very effective in reducing the microbial flora, including L. pneumophila. Heterotrophic bacteria, although strongly reduced, were still detectable after ozone application (0.5 mg l(-1)), whereas with monochloramine (0.5 mg l(-1)) and copper-silver ionization (0.8/0.02 mg l(-1)), the contamination remained significantly higher. Monochloramine and copper-silver did not remove the biofilm. During copper-silver application, Legionella re-growth was observed. Only chlorine dioxide led to detectable effects in the dead leg. Amoebae could not be eliminated, and after interrupting the treatments, L. pneumophila quickly recovered their initial levels, in all cases. CONCLUSIONS: Chlorine dioxide, applied as a continuous treatment, was identified in this study as the most efficient for controlling L. pneumophila in a domestic water system. Chlorine dioxide showed a longer residual activity, leading to improved performance in the dead leg. Amoebae resisted to all the treatments applied and probably acted as reservoirs for L. pneumophila, allowing a quick re-colonization of the system once the treatments were interrupted. SIGNIFICANCE AND IMPACT OF THE STUDY: Control of microbial contamination requires maintenance of a constant disinfectant residual throughout the water system. Treatment strategies targeting free-living amoebae should lead to improved control of L. pneumophila. Such treatment strategies still have to be investigated.



From legionnaire to guerrilla combatant: suppression of Legionella pneumophila in a hospital cold water supply

Wagenvoort JH, Sijstermans ML.

Department of Medical Microbiology, Atrium Medical Centre, P.O. Box 4446, 6401 CX, The Netherlands. medische.microbiologie@atriummc.nl

J Hosp Infect. 2004 Oct;58(2):162-3.



Investigation of opportunistic pathogens in municipal drinking water under different supply and treatment regimes

Pryor M, Springthorpe S, Riffard S, Brooks T, Huo Y, Davis G, Sattar SA.

Pinellas County Utilities Laboratory, Largo, FL, USA. ssattar@uottawa.ca

Water Sci Technol. 2004;50(1):83-90.

ABSTRACT: Changing regulations to lower disinfectant byproducts in drinking water is forcing utilities to switch disinfection from chlorine to monochloramine. It is generally unknown whether this will impact positively or negatively on the microbiological quality of drinking water. A utility in Florida, using water with relatively high organic carbon levels from deep wells in several wellfields, made the decision to change its disinfection regime from chlorine to chloramine in order to meet the new regulations. To assess the impacts of such a change on the microbiology of its water supplies, it undertook a number of studies before and after the change. In particular, the presence of the opportunistic pathogens Legionella and Mycobacterium, and also the composition of drinking-water biofilms, were examined. A preliminary synthesis and summary of these results are presented here. Legionella species were widely distributed in source waters and in the distribution system when chlorine was the disinfectant. In some samples they seemed to be among the dominant biofilm bacteria. Following the change to monochloramine, legionellae were not detected in the distribution system during several months of survey; however, they remained detectable at point of use, although with less species diversity. A variety of mycobacteria (21 types) were widely distributed in the distribution system when chlorine was the disinfectant, but these seemed to increase in dominance after chloramination was instituted. At point of use, only four species of mycobacteria were detected. Other changes occurring with chloramination included (a) an altered biofilm composition, (b) increased numbers of total coliforms and heterotrophs and (c) nitrification of water storage tanks. The results suggested that consideration should be given to the microbiological effects of changing disinfection regimes in drinking-water and distribution system biofilms.


Biofilms, thermophilic amoebae and Legionella pneumophila--a quantitative risk assessment for distributed water

Storey MV, Ashbolt J, Stenstrom TA.

Dept of Water and Environmental Microbiology, Swedish Institute for Infectious Disease Control, SE-171 82 Solna, Sweden. michael.storey@smi.ki.se

Water Sci Technol. 2004;50(1):77-82

ABSTRACT: A simplistic quantitative microbial risk assessment (QMRA) based on the maximum risk curve (r = 1) was developed for Legionella within a water distribution system. Both biofilms and a thermophilic isolate of acanthamoebae were shown to increase the resistance of Legionella to conventional thermal disinfection by between one and two logs respectively. The level of risk presented to consumers was shown to exceed the USEPA 10(-4) benchmark in many cases tested. This was caused, in part, by the sensitivity of the risk model but also through a lack of reliable dose-response data for Legionella. Not withstanding this, the current study provided comparative information on the efficacy of conventional disinfection against Legionella. Combined chlorine was shown to reduce the risk of infection by as much as 1-log when compared to free chlorine, although thermal disinfection provided the most effective means of risk reduction. Biofilm detachment and the interaction of Legionella with acanthamoebae were two important ecological factors that significantly increased the risk of legionellosis, and thus should be further considered in the refinement of QMRA models.


Water disinfection by electrochemical treatment

Feng C, Suzuki K, Zhao S, Sugiura N, Shimada S, Maekawa T.

Project for Water Environment Renovation of Lake Kasumigaura, The Science and Technology Promotion of Ibaraki, A34, Tsukuba Center Inco., 2-1-6 Sengen, Ibaraki, Tsukuba 305-0047, Japan. fchuanpg@i-step.org

Bioresour Technol. 2004 Aug;94(1):21-5.

ABSTRACT: The electrochemical disinfection of germinated brown rice (GBR) circulating water and cooling tower water containing Legionella bacteria was investigated. Results showed the total aerobic plate counts (APC) in the treated GBR circulating water decreased significantly and the turbidity was largely improved at a pulse voltage of 1.0 kV; Legionella bacteria were also disinfected effectively at 1.0 kV. The disinfection was attributed to the synergistic effects of the oxide anode, the electric field, and the radicals formed during the electrochemical treatment. This suggests that electrochemical treatment could be applicable to the disinfection of water from other sources.




Photoreactivation of Legionella pneumophila after inactivation by low- or medium-pressure ultraviolet lamp

Oguma K, Katayama H, Ohgaki S.

Department of Urban Engineering, Graduate school of Engineering, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan. oguma@env.t.u-tokyo.ac.jp

Water Res. 2004 Jun;38(11):2757-63.

ABSTRACT: Photoreactivation of Legionella pneumophila after the inactivation by low-pressure (LP) or medium-pressure (MP) UV lamp was investigated in comparison with that of Escherichia coli. An endonuclease sensitive site (ESS) assay was used to determine the number of UV-induced pyrimidine dimers in the genome DNA of L. pneumophila or E. coli, while the survival ratio of each bacterium was also investigated by cultivation methods. L. pneumophila performed photoreactivation with almost complete repair of pyrimidine dimers associated with the quick recovery of survival ratio. A 3log inactivation of L. pneumophila by LP or MP UV lamp was, respectively, resulted in 0.5log or 0.4log inactivation when photoreactivation was completed. Interestingly, L. pneumophila performed equivalent photoreactivation after LP and MP UV lamp exposures while photoreactivation of E. coli was significantly repressed after the inactivation by MP UV lamp. This study indicated that an attention would be required to design and operate a UV disinfection system targeting L. pneumophila. It was further implied that E. coli would not correctly indicate the fate of L. pneumophila in UV disinfection systems when photoreactivation takes place.



Evaluation of disinfective potential of reactivated free chlorine in pooled tap water by electrolysis

Nakajima N, Nakano T, Harada F, Taniguchi H, Yokoyama I, Hirose J, Daikoku E, Sano K.

Department of Microbiology, Osaka Medical College, 2-7 Daigaku-machi Takatsuki, Osaka 569-8686, Japan. tnakano@art.osaka-med.ac.jp

J Microbiol Methods. 2004 May;57(2):163-73.

ABSTRACT: Tap water is one of the causative factors of hospital infections. We examined the disinfective potential of electrolysis and mechanism of disinfection, and clarified the disinfective effect of electrolysis on tap water contaminated with bacteria, and discussed its clinical applications. Tap waters artificially contaminated with Pseudomonas aeruginosa, Escherichia coli, Legionella pneumophila, and Staphylococcus aureus could be sterilized by electrolysis at 20-30 mA for 5 min. A high-density suspension (10(6) CFU/ml) of a spore forming bacterium, Bacillus subtilis was not completely sterilized by electrolysis at 50 mA up to 30 min, but a low-density suspension (10(5) CFU/ml) was totally sterilized by electrolysis at 50 mA for 5 min. Electrolyzed P. aeruginosa changed morphologically, that is, there was bleb formation on the cell wall and irregular aggregation of cytoplasmic small granules. Moreover, cytoplasmic enzyme, nitrate reductase, was inactivated by the electrolysis. On the other hand, genomic DNA of the electrolyzed bacteria was not degenerated, therefore, their DNA polymerase activity was not completely inactivated. Consequently, the major agent in electrolysis for bactericidal action was considered to be free chlorine, and the possible bactericidal mechanism was by destruction of bacterial membranes, followed by the aggregation of peripheral cytoplasmic proteins. Electrolysis of tap water for both disinfecting contaminating bacteria and increasing the disinfectant capacity was considered effective with some limitations, particularly against high-density contamination by spore-forming bacteria. In clinical settings, electrolysis of tap water is considered effective to disinfect water for hand washing in operation theatres, and bathing water for immunocompromised hosts.  



Assessment of a novel approach to evaluate the outcome of endoscope reprocessing

Sciortino CV Jr, Xia EL, Mozee A.

Department of Pathology and Laboratory Medicine, Department of Veterans Affairs Medical Center, 800 Zorn Avenue, Louisville, KY 40206, USA.

Infect Control Hosp Epidemiol. 2004 Apr;25(4):284-90.

ABSTRACT: OBJECTIVE: To investigate and evaluate the use of a portable luminometer system for detecting contamination following the reprocessing and high-level disinfection of flexible endoscopes. DESIGN: Random sampling of endoscopes spaced at 1- to 2-week intervals following normal use in patients. METHODS: Portable luminometer system testing of 31 endoscopes undergoing reprocessing, 63 stored endoscopes, and 15 reprocessed endoscopes that underwent in-depth microbiological analysis. For testing with the portable luminometer system, samples were collected by swabbing a 100-cm2 shank surface area and the internal tip end orifice. Standardization of portable luminometer system results was performed in vitro by comparison of serial dilutions of known quantities of microorganisms and blood, tested before and after sterilization by autoclave. Microbiological analysis included Gram stain, culture for aerobic bacteria, and gene probes for Mycobacterium tuberculosis, herpes simplex viruses 1 and 2, and Cytomegalovirus. Trichrome and calcofluor white stains were used to detect parasites and fungi. Legionella was detected by stain with fluorescent-labeled monoclonal antibody. SETTING: The gastroendoscopy unit of a Veterans Affairs hospital. RESULTS: The portable luminometer system was capable of detecting microbial and cellular contamination of flexible endoscopes following high-level disinfection and reprocessing. The sensitivity of the assay was sufficient for detecting low-level contamination. CONCLUSIONS: The system provided a rapid microbiological outcome monitor for the cleaning and disinfection process. The system was easy to use and relatively accurate.



Formation of natural biofilms during chlorine dioxide and u.v. disinfection in a public drinking water distribution system

Schwartz T, Hoffmann S, Obst U.

Department of Environmental Microbiology, Water Technology and Geotechnology Division, Institute for Technical Chemistry, Forschungszentrum Karlsruhe GmbH, Karlsruhe, Germany. thomas.schwartz@itc-wgt.fzk.de

J Appl Microbiol. 2003 sep;95(3):591-601.

ABSTRACT: AIMS: The influence of two disinfection techniques on natural biofilm development during drinking water treatment and subsequent distribution is compared with regard to the supply of a high-quality drinking water. METHODS AND RESULTS: The growth of biofilms was studied using the biofilm device technique in a real public technical drinking water asset. Different pipe materials which are commonly used in drinking water facilities (hardened polyethylene, polyvinyl chloride, steel and copper) were used as substrates for biofilm formation. Apart from young biofilms, several months old biofilms were compared in terms of material dependence, biomass and physiological state. Vital staining of biofilms with 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) and the DNA-specific 4',6-diamidino-2-phenylindole (DAPI) staining resulted in a significant difference in physiological behaviour of biofilm populations depending on the disinfection technique. Compared with chlorine dioxide disinfection (0.12-0.16 mg l-1), the respiratory activities of the micro-organisms were increased on all materials during u.v. disinfection (u.v.254; 400 J m-2). The biofilm biocoenosis was analysed by in situ hybridization with labelled oligonucleotides specific for some subclasses of Proteobacteria. Using PCR and additional hybridization techniques, the biofilms were also tested for the presence of Legionella spp., atypical mycobacteria and enterococci. The results of the molecular-biological experiments in combination with cultivation tests showed that enterococci were able to pass the u.v. disinfection barrier and persist in biofilms of the distribution system, but not after chlorine dioxide disinfection. CONCLUSIONS: The results indicated that bacteria are able to regenerate and proliferate more effectively after u.v. irradiation at the waterworks, and chlorine dioxide disinfection appears to be more applicative to maintain a biological stable drinking water. SIGNIFICANCE AND IMPACT OF THE STUDY: As far as the application of u.v. disinfection is used for conditioning of critical water sources for drinking water, the efficiency of u.v. irradiation in natural systems should reach a high standard to avoid adverse impacts on human health.



Growth of Escherichia coli in model distribution system biofilms exposed to hypochlorous acid or monochloramine

Williams MM, Braun-Howland EB.
Wadsworth Center, New York State Department of Health, Albany, New York 12201, USA.


Appl Environ Microbiol. 2003 Sep;69(9):5463-71

ABSTRACT: Bacteria indigenous to water distribution systems were used to grow multispecies biofilms within continuous-flow slide chambers. Six flow chambers were also inoculated with an Escherichia coli isolate obtained from potable water. The effect of disinfectants on bacterial populations was determined after exposure of established biofilms to 1 ppm of hypochlorous acid (ClOH) for 67 min or 4 ppm of monochloramine (NH(2)Cl) for 155 min. To test the ability of bacterial populations to initiate biofilm formation in the presence of disinfectants, we assessed the biofilms after 2 weeks of exposure to residual concentrations of 0.2 ppm of ClOH or 4 ppm of NH(2)Cl. Lastly, to determine the effect of recommended residual concentrations on newly established biofilms, we treated systems with 0.2 ppm of ClOH after 5 days of growth in the absence of disinfectant. Whole-cell in situ hybridizations using fluorescently tagged, 16S rRNA-targeted oligonucleotide probes performed on cryosectioned biofilms permitted the direct observation of metabolically active bacterial populations, including certain phylogenetic groups and species. The results of these studies confirmed the resistance of established bacterial biofilms to treatment with recommended levels of disinfectants. Specifically, Legionella pneumophila, E. coli, and beta and delta proteobacteria were identified within biofilms both before and after treatment. Furthermore, although it was undetected using routine monitoring techniques, the observation of rRNA-containing E. coli within biofilms demonstrated not only survival but also metabolic activity of this organism within the model distribution systems. The persistence of diverse bacterial species within disinfectant-treated biofilms suggests that current testing practices underestimate the risk to immunocompromised individuals of contracting waterborne disease.



Experiences of the first 16 hospitals using copper-silver ionization for Legionella control: implications for the evaluation of other disinfection modalities
Stout JE, Yu VL.

Special Pathogens Laboratory, Veterans Affairs Medical Center, Pittsburg, Pennsylvania 15240, USA.


Infect Control Hosp Epidemiol. 2003 Aug;24(8):563-8.

ABSTRACT: BACKGROUND AND OBJECTIVES: Hospital-acquired legionnaires' disease can be prevented by disinfection of hospital water systems. This study assessed the long-term efficacy of copper-silver ionization as a disinfection method in controlling Legionella in hospital water systems and reducing the incidence of hospital-acquired legionnaires' disease. A standardized, evidence-based approach to assist hospitals with decision making concerning the possible purchase of a disinfection system is presented. DESIGN: The first 16 hospitals to install copper-silver ionization systems for Legionella disinfection were surveyed. Surveys conducted in 1995 and 2000 documented the experiences of the hospitals with maintenance of the system, contamination of water with Legionella, and occurrence of hospital-acquired legionnaires' disease. All were acute care hospitals with a mean of 435 beds. RESULTS: All 16 hospitals reported cases of hospital-acquired legionnaires' disease prior to installing the copper-silver ionization system. Seventy-five percent had previously attempted other disinfection methods including superheat and flush, ultraviolet light, and hyperchlorination. By 2000, the ionization systems had been operational from 5 to 11 years. Prior to installation, 47% of the hospitals reported that more than 30% of distal water sites yielded Legionella. In 1995, after installation, 50% of the hospitals reported 0% positivity, and 43% still reported 0% in 2000. Moreover, no cases of hospital-acquired legionnaires' disease have occurred in any hospital since 1995. CONCLUSIONS: This study represents the final step in a proposed 4-step evaluation process of disinfection systems that includes (1) demonstrated efficacy of Legionella eradication in vitro using laboratory assays, (2) anecdotal experiences in preventing legionnaires' disease in individual hospitals, (3) controlled studies in individual hospitals, and (4) validation in confirmatory reports from multiple hospitals during a prolonged time (5 to 11 years in this study). Copper-silver ionization is now the only disinfection modality to have fulfilled all four evaluation criteria.


A 17-month evaluation of a chlorine dioxide water treatment system to control Legionella species in a hospital water supply
Srinivasan A, Bova G, Ross T, Mackie K, Paquette N, Merz W, Perl TM.
Department of Medicine, Division of Infectious Diseases, Hospital Epidemiology and Infection Control, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA.
Address reprint requests to Trish Perl, MD, MSc, Johns Hopkins Hospital, 600 N. Wolfe St., Osler Building, Room 425, Baltimore, MD 21287.

Infect Control Hosp Epidemiol. 2003 Aug;24(8):575-9.

ABSTRACT: OBJECTIVE: To assess the safety and efficacy of a chlorine dioxide water treatment system in controlling Legionella in a hospital water supply. DESIGN: For 17 months following installation of the system, we performed regular water cultures throughout the building, assessed chlorine dioxide and chlorite levels, and monitored metal corrosion. RESULTS: Sites that grew Legionella species decreased from 41% at baseline to 4% (P = .001). L. anisa was the only species recovered and it was found in samples of both hot and cold water. Levels of chlorine dioxide and chlorite were below Environmental Protection Agency (EPA) limits for these chemicals in potable water. Further, enhanced carbon filtration effectively removed the chemicals, even at chlorine dioxide levels of more than twice what was used to treat the water. After 9 months, corrosion of copper test strips exposed to the chlorine dioxide was not higher than that of control strips. During the evaluation period, there were no cases of nosocomial Legionella in the building with the system, whereas there was one case in another building. CONCLUSIONS: Our results indicate that operation of a chlorine dioxide system effectively removed Legionella species from a hospital water supply. Furthermore, we found that the system was safe, as levels of chlorine dioxide and chlorite were below EPA limits. The system did not appear to cause increased corrosion of copper pipes. Our results indicate that chlorine dioxide may hold promise as a solution to the problem of Legionella contamination of hospital water supplies.



Risk of hospital-acquired legionnaires' disease in cities using monochloramine versus other water disinfectants

Heffelfinger JD, Kool JL, Fridkin S, Fraser VJ, Hageman J, Carpenter J, Whitney CG; Society for Healthcare Epidemiology of America. jkool@cdc.gov

Infect Control Hosp Epidemiol. 2003 Aug;24(8):569-74.

ABSTRACT: OBJECTIVE: To measure the association between the disinfection of municipal drinking water with monochloramine and the occurrence of hospital-acquired legionnaires' disease (LD). SETTING: One hundred sixty-six U.S. hospitals. DESIGN: Survey of 459 members of the Society for Healthcare Epidemiology of America (SHEA) for hospital features; endemic- and outbreak-related, hospital-acquired LD; the source of the hospital water supply; and the methods of disinfection used by the hospitals and municipal water treatment plants. RESULTS: SHEA members representing 166 (36%) of 459 hospitals responded; 33 (20%) reported one or more episodes of hospital-acquired LD during the period from 1994 to 1998 and 23 (14%) reported an outbreak of hospital-acquired LD during the period from 1989 to 1998. Hospitals with an occurrence of hospital-acquired LD had a higher census (median, 319 vs 221; P = .03), more acute care beds (median, 500 vs 376; P = .04), and more intensive care unit beds (median, 42 vs 24; P = .009) than did other hospitals. They were also more likely to have a transplant service (74% vs 42%; P = .001) and to perform surveillance for hospital-acquired disease (92% vs 61%; P = .001). After adjustment for the presence of a transplant program and surveillance for legionnaires' disease, hospitals supplied with drinking water disinfected with monochloramine by municipal plants were less likely to have sporadic cases or outbreaks of hospital-acquired LD (odds ratio, 0.20; 95% confidence interval, 0.07 to 0.56) than were other hospitals. CONCLUSION: Water disinfection with monochloramine by municipal water treatment plants significantly reduces the risk of hospital-acquired LD.




Ultraviolet light disinfection of hospital water for preventing nosocomial Legionella infection: a 13-year follow-up
Hall KK, Giannetta ET, Getchell-White SI, Durbin LJ, Farr BM.
University of Virginia Health System, Charlottesville, Virginia 22908-1337, USA.


Infect Control Hosp Epidemiol. 2003 Aug;24(8):580-3

ABSTRACT: BACKGROUND AND OBJECTIVE: CDC has estimated that 23% of Legionella infections are nosocomial. When a new hospital was being constructed and a substantial increase in transplantation was anticipated, an ultraviolet light apparatus was installed in the water main of the new building because 27% of water samples from taps in the old hospital contained Legionella. This study reports the rate of nosocomial Legionella infection and water contamination since opening the new hospital. METHODS: Charts of all patients with positive Legionella cultures, direct immunofluorescent antibody (DFA), or urine antigen between April 1989 and November 2001 were reviewed. Frequencies of DFAs and urine antigens were obtained from the laboratory. RESULTS: None of the 930 cultures of hospital water have been positive since moving into the new building. Fifty-three (0.02%) of 219,521 patients had a positive Legionella test; 41 had pneumonia (40 community acquired). One definite L. pneumophila pneumonia confirmed by culture and DFA in August 1994 was nosocomial (0.0005%) by dates. This patient was transferred after prolonged hospitalization in another country, was transplanted 11 days after admission, and developed symptoms 5 days after liver transplant. However, tap water from the patient's room did not grow Legionella. Seventeen (2.5%) of 670 urine antigens were positive for Legionella (none nosocomial). Thirty-three (1.2%) of 2,671 DFAs were positive, including 7 patients (21%) without evidence of pneumonia and 6 (18%) who had an alternative diagnosis. CONCLUSION: Ultraviolet light usage was associated with negative water cultures and lack of clearly documented nosocomial Legionella infection for 13 years at this hospital.


Colonization of hospital water systems by legionellae, mycobacteria and other heterotrophic bacteria potentially hazardous to risk group patients

Kusnetsov J, Torvinen E, Perola O, Nousiainen T, Katila ML.

Laboratory of Environmental Microbiology, National Public Health Institute, Kuopio, Finland. Jaana.Kusnetsov@ktl.fi

APMIS. 2003 May;111(5):546-56.

ABSTRACT: Occurrences of legionellae and nontuberculous mycobacteria were followed in water systems of a tertiary care hospital where nosocomial infections due to the two genera had been verified. The aim was to examine whether their occurrence in the circulating hot water can be controlled by addition of a heat-shock unit in the circulation system, and by intensified cleaning of the tap and shower heads. One hot water system examined had an inbuilt heat-shock system causing a temporary increase of temperature to 80 degrees C, the other was an ordinary system (60 degrees C). The heat-shock unit decreased legionella colony counts in the circulating hot water (mean 35 cfu/l) compared to the ordinary system (mean 3.6 x 10(3) cfu/l). Mycobacteria constantly present in the incoming cold water (mean 260 cfu/l) were never isolated from the circulating hot water. Water sampled at peripheral sites such as taps and showers contained higher concentrations of legionellae, mycobacteria, and mesophilic and Gram-negative heterotrophs than the circulating waters. The shower water samples contained the highest bacterial loads. The results indicate the need to develop more efficient prevention methods than the ones presently used. Prevention of mycobacteria should also be extended to incoming cold water.


Hygienic quality of the water of public swimming pools - comments on a current german ordinance draft

[Article in German]

Hentschel W, Heudorf U.

Gesundheitsamt der Stadt Frankfurt am Main. wolfgang.hentschel@stadt-frankfurt.de

Gesundheitswesen. 2003 Apr; 65(4): 255-62

ABSTRACT: In April 2002, a new draft regarding the quality of the water of public swimming pools in Germany was published. This draft was adapted to the new regulations for drinking water in respect of its structure and regulations. Microbiological tests for assessing the quality of bathing water are given priority. With regard to basic differences in facilities for drinking water and such for bath water and to legal aspects, many data (n = 14,425 data) on the practical experience of public health authorities are presented, obtained during the last few years. With regard to the data and in respect of the great delay between sampling and obtaining the results it is concluded that microbiological methods are inappropriate parameters for rapid assessment of the quality of bath water. Hence it is recommended to implement the evaluation of disinfection by chlorination including pH as an indicator for the quality of a bath water, parallel to the guidelines on technical standards. A high frequency of chlorination testing can markedly reduce the number of microbiological tests. Additionally, microbiological tests of the filtrate before disinfection by chlorination are recommended. This procedure has proved successful in legionella control.