Disinfezione (2020 - 2017)
[ultimo aggiornamento 25/11/2020]
Martin RL, Harrison K,
Proctor CR, Martin A, Williams K, Pruden A, Edwards MA.
Department of Civil and
Environmental Engineering, Virginia Tech, Blacksburg, VA, USA. edwardsm@vt.edu
Microorganisms 2020 Sep
22;8(9):1452.
Abstract: Premise
plumbing conditions can contribute to low chlorine or chloramine disinfectant
residuals and reactions that encourage opportunistic pathogen growth and create
risk of Legionnaires' Disease outbreaks. This bench-scale study investigated the
growth of Legionella spp. and Acanthamoeba in
direct contact with premise plumbing materials-glass-only control, cross-linked
polyethylene (PEX) pipe, magnesium anode rods, iron pipe, iron oxide, pH 10, or
a combination of factors. Simulated glass water heaters (SGWHs) were colonized
by Legionella pneumophila and exposed to a sequence of 0, 0.1,
0.25, and 0.5 mg/L chlorine or chloramine, at two levels of total organic carbon
(TOC), over 8 weeks. Legionella pneumophila thrived in the
presence of the magnesium anode by itself and or combination with other factors.
In most cases, 0.5 mg/L Cl2 caused a significant rapid reduction
of L. pneumophila, Legionella spp., or total
bacteria (16S rRNA) gene copy numbers, but at higher TOC (>1.0 mg C/L), a
chlorine residual of 0.5 mg/L Cl2 was not effective. Notably, Acanthamoeba was
not significantly reduced by the 0.5 mg/L chlorine dose.
Interactive Effects of
Copper Pipe, Stagnation, Corrosion Control, and Disinfectant Residual Influenced
Reduction of Legionella pneumophila during Simulations of the
Flint Water Crisis
Martin RL, Strom OR,
Pruden A, Edwards MA.
Department of Civil and
Environmental Engineering, Virginia Tech, Blacksburg, VA, USA. edwardsm@vt.edu
Pathogens 2020 Sep
4;9(9):730.
Abstract: Flint,
MI experienced two outbreaks of Legionnaires' Disease (LD) during the summers of
2014 and 2015, coinciding with use of Flint River as a drinking water source
without corrosion control. Using simulated distribution systems (SDSs) followed
by stagnant simulated premise (i.e., building) plumbing reactors (SPPRs)
containing cross-linked polyethylene (PEX) or copper pipe, we reproduced trends
in water chemistry and Legionella proliferation observed in the
field when Flint River versus Detroit water were used before, during, and after
the outbreak. Specifically, due to high chlorine demand in the SDSs, SPPRs with
treated Flint River water were chlorine deficient and had elevated L.
pneumophila numbers in the PEX condition. SPPRs with Detroit water,
which had lower chlorine demand and higher residual chlorine, lost all
culturable L. pneumophila within two months. L.
pneumophila also diminished more rapidly with time in Flint River SPPRs
with copper pipe, presumably due to the bacteriostatic properties of elevated
copper concentrations caused by lack of corrosion control and stagnation. This
study confirms hypothesized mechanisms by which the switch in water chemistry,
pipe materials, and different flow patterns in Flint premise plumbing may have
contributed to observed LD outbreak patterns.
Safety and Effectiveness
of Monochloramine Treatment for Disinfecting Hospital Water Networks
Marchesi I, Paduano S, Frezza G, Sircana L, Vecchi E,
Zuccarello P, Oliveri Conti G, Ferrante M, Borella P, Bargellini A.
Department
of Biomedical, Metabolic and Neural Sciences, Section of Public Health,
University of Modena and Reggio Emilia, Modena, Italy. Isabella.marchesi@unimore.it
Int J Environ Res Public
Health 2020 Aug 22;17(17):6116.
Abstract: The
formation of potentially carcinogenic N-nitrosamines, associated with
monochloramine, requires further research due to the growing interest in using
this biocide for the secondary disinfection of water in public and private
buildings. The aim of our study was to evaluate the possible formation of
N-nitrosamines and other toxic disinfection by-products (DBPs) in hospital hot
water networks treated with monochloramine. The effectiveness of this biocide in
controlling Legionella spp. contamination was also verified.
For this purpose, four different monochloramine-treated networks, in terms of
the duration of treatment and method of biocide injection, were investigated.
Untreated hot water, municipal cold water and, limited to N-nitrosamines
analysis, hot water treated with chlorine dioxide were analyzed for comparison. Legionella spp.
contamination was successfully controlled without any formation of
N-nitrosamines. No nitrification or formation of the regulated DBPs, such as
chlorites and trihalomethanes, occurred in monochloramine-treated water networks.
However, a stable formulation of hypochlorite, its frequent replacement with a
fresh product, and the routine monitoring of free ammonia are recommended to
ensure a proper disinfection. Our study confirms that monochloramine may be
proposed as an effective and safe strategy for the continuous disinfection of
building plumbing systems, preventing vulnerable individuals from being exposed
to legionellae and dangerous DBPs.
Legionella pneumophila and Protozoan Hosts:
Implications for the Control of Hospital and Potable Water Systems
Nisar MA, Ross KE, Brown MH,
Bentham R, Whiley H.
College of Science and Engineering, Flinders
University, Adelaide, Australia. Harriet.Whiley@flinders.edu.au
Pathogens
2020 Apr 15;9(4):286.
Abstract: Legionella
pneumophila is an opportunistic waterborne pathogen of public health
concern. It is the causative agent of Legionnaires' disease (LD) and Pontiac
fever and is ubiquitous in manufactured water systems, where protozoan hosts and
complex microbial communities provide protection from disinfection procedures.
This review collates the literature describing interactions between L.
pneumophila and protozoan hosts in hospital and municipal potable water
distribution systems. The effectiveness of currently available water
disinfection protocols to control L. pneumophila and its
protozoan hosts is explored. The studies identified in this systematic
literature review demonstrated the failure of common disinfection procedures to
achieve long term elimination of L. pneumophila and protozoan
hosts from potable water. It has been demonstrated that protozoan hosts
facilitate the intracellular replication and packaging of viable L.
pneumophila in infectious vesicles; whereas, cyst-forming protozoans
provide protection from prolonged environmental stress. Disinfection procedures
and protozoan hosts also facilitate biogenesis of viable but non-culturable (VBNC) L.
pneumophila which have been shown to be highly resistant to many water
disinfection protocols. In conclusion, a better understanding of L.
pneumophila-protozoan interactions and the structure of complex microbial
biofilms is required for the improved management of L. pneumophila and
the prevention of LD.
Persistent Legionella
contamination of water faucets in a tertiary hospital in Japan
Nakamura I,
Amemura-Maekawa J, Kura F, Kobayashi T, Sato A, Watanabe H, Matsumoto T.
Department of Infection Prevention and Control, Tokyo Medical
University Hospital, Tokyo, Japan. task300@tokyo-med.ac.jp
Int J Infect Dis 2020
Apr;93:300-304.
Abstract: Objective: The feasibility of the
decontamination procedure for Legionella
pneumophila of water systems in healthcare facilities varies by water
purification and disinfection methods in each country. We evaluated the efficacy
of feasible decontamination strategies in Japan. Methods: This
study was conducted at Tokyo Medical University Hospital (1015 beds) between
2015 and 2018. Samples from the water system and cooling tower were cultured
periodically. Hyper-chlorination of cool tap water (>0.2 ppm), increases in
the temperature of hot water (>55 °C), and flushing were used as
decontamination strategies. The case of healthcare-associated legionellosis was
surveyed. Environmental and clinical isolates were genotyped. Results: 1439 environmental samples were collected; 19 (1.3%)
samples tested positive for L. pneumophila
from water faucets of patient rooms, toilets, waste rooms, and water sourced
from wells. Genotyping of 12 isolates confirmed that the same strains were
present in eight environmental isolates and two isolates from patients over
three years. Although the environmental contamination of the water system was
persistent, the number of positive locations of hospital environments gradually
decreased; eight in 2015, four in 2016, three in 2017, and four in 2018,
respectively. Conclusions: Monitoring
contamination, hyper-chlorination, controlling temperature, and flushing were
effective as a Legionella decontamination strategy.
Effect of disinfectant
residuals on infection risks from Legionella
pneumophila released by biofilms grown under simulated premise plumbing
conditions
Huang C, Shen Y, Smith
RL, Dong S, Nguyen TH.
Department of Civil and
Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana,
IL, USA. thn@illinois.edu
Environ Int 2020 Apr;137:105561.
Abstract: The
ubiquitous presence of biofilms in premise plumbing and stagnation, which
commonly occurs in premise plumbing, can exacerbate the decay of chlorine
residual in drinking water. Using biofilms grown in a simulated premise plumbing
setup fed directly with freshly treated water at two full-scale water treatment
plants, we previously determined the mass transfer coefficients for chlorine
decay in premise plumbing. These coefficients coupled with inactivation kinetics
of L. pneumophila released from
biofilms reported previously were integrated into a Monte Carlo framework to
estimate the infection risk of biofilm-derived L.
pneumophila from 1 to 48 h of stagnation. The annual infection risk was
significantly higher when water stayed stagnant for up to 48 h in pipes covered
internally with biofilms, compared to clean pipes without biofilms. The decay of
residual chlorine due to biofilms during 48-hour stagnation led to up to 6 times
increase in the annual infection risk compared to the case where biofilms was
absent. Global sensitivity analysis revealed that the rate of L.
pneumophila detachment from biofilms and the decay of chlorine residual
during stagnation are the two most important factors influencing the infection
risks. Stagnation caused by water use patterns and water-saving devices in the
premise plumbing can lead to increased infection risk by biofilm-derived L.
pneumophila. Overall, this study's findings suggested that biofilms could
induce chlorine decay and consequently increase L. pneumophila infection risk. Thus, reducing stagnation,
maintaining residual chlorine, and suppressing biofilm growth could contribute
to better management of L. pneumophila
infection risk.
Photocatalytic biocidal
effect of copper doped TiO2 nanotube coated surfaces under laminar flow,
illuminated with UVA light on Legionella
pneumophila
Oder M, Koklič T,
Umek P, Podlipec R, Štrancar J, Dobeic M.
Institute of Food Safety
Feed and Environment, University of Ljubljana, Veterinary Faculty, Ljubljana,
Slovenia. martin.dobeic@vf.uni-lj.si
PLoS One 2020 Jan
15;15(1):e0227574.
Abstract: Legionella
pneumophila can cause a potentially fatal form
of humane pneumonia (Legionnaires' disease), which is most problematic in
immunocompromised and in elderly people. Legionella
species is present at low concentrations in soil, natural and artificial aquatic
systems and is therefore constantly entering man-made water systems. The
environment temperature for it's ideal growth range is between 32 and 42°C,
thus hot water pipes represent ideal environment for spread of Legionella. The bacteria are dormant below 20°C and do not survive
above 60°C. The primary method used to control the risk from Legionella
is therefore water temperature control. There are several other effective
treatments to prevent growth of Legionella in water systems, however current
disinfection methods can be applied only intermittently thus allowing Legionella
to grow in between treatments. Here we present an alternative disinfection
method based on antibacterial coatings with Cu-TiO2 nanotubes deposited on
preformed surfaces. In the experiment the microbiocidal efficiency of submicron
coatings on polystyrene to the bacterium of the genus Legionella
pneumophila with a potential use in a water supply system was tested. The
treatment thus constantly prevents growth of Legionella pneumophila in presence of water at room temperature.
Here we show that 24-hour illumination with low power UVA light source (15 W/m2
UVA illumination) of copper doped TiO2 nanotube coated surfaces is effective in
preventing growth of Legionella
pneumophila. Microbiocidal effects of Cu-TiO2 nanotube coatings were
dependent on the flow of the medium and the intensity of UV-A light. It was
determined that tested submicron coatings have microbiocidal effects specially
in a non-flow or low-flow conditions, as in higher flow rates, probably to a
greater possibility of Legionella
pneumophila sedimentation on the coated polystyrene surfaces, meanwhile no
significant differences among bacteria reduction was noted regarding to non or
low flow of medium.
Photocatalytic biocidal effect of copper doped TiO2 nanotube
coated surfaces under laminar flow, illuminated with UVA light on Legionella pneumophila
Oder M, Koklič T, Umek P,
Podlipec R, Štrancar J, Dobeic M.
Institute of Food Safety Feed and
Environment, University of Ljubljana, Veterinary Faculty, Ljubljana, Slovenia. martin.dobeic@vf.uni-lj.si
PLoS
One 2020 Jan;15(1):e0227574.
Abstract: Legionella pneumophila can cause a potentially fatal form of
humane pneumonia (Legionnaires' disease), which is most problematic in
immunocompromised and in elderly people. Legionella species is
present at low concentrations in soil, natural and artificial aquatic systems
and is therefore constantly entering man-made water systems. The environment
temperature for its ideal growth range is between 32 and 42°C, thus hot water
pipes represent ideal environment for spread of Legionella. The
bacteria are dormant below 20°C and do not survive above 60°C. The primary
method used to control the risk from Legionella is therefore
water temperature control. There are several other effective treatments to
prevent growth of Legionella in water systems, however current
disinfection methods can be applied only intermittently thus allowing Legionella to
grow in between treatments. Here we present an alternative disinfection method
based on antibacterial coatings with Cu-TiO2 nanotubes deposited on
preformed surfaces. In the experiment the microbiocidal efficiency of submicron
coatings on polystyrene to the bacterium of the genus Legionella pneumophila
with a potential use in a water supply system was tested. The treatment thus
constantly prevents growth of Legionella pneumophila in
presence of water at room temperature. Here we show that 24-hour illumination
with low power UVA light source (15 W/m2 UVA illumination) of copper
doped TiO2 nanotube coated surfaces is effective in preventing growth
of Legionella pneumophila. Microbiocidal effects of Cu-TiO2
nanotube coatings were dependent on the flow of the medium and the intensity of
UV-A light. It was determined that tested submicron coatings have microbiocidal
effects specially in a non-flow or low-flow conditions, as in higher flow rates,
probably to a greater possibility of Legionella pneumophila
sedimentation on the coated polystyrene surfaces, meanwhile no significant
differences among bacteria reduction was noted regarding to non or low flow of
medium.
Donohue MJ, Vesper S, Mistry J, Donohue JM.
U.S.
Environmental Protection Agency, Cincinnati, Ohio, USA. Donohue.maura@epa.gov
Appl Environ Microbiol 2019 Nov;85(24):e01942-19.
Abstract:
Potable water can be a source of transmission for legionellosis and
nontuberculous mycobacterium (NTM) infections and diseases. Legionellosis is
caused largely by Legionella pneumophila, specifically serogroup 1
(Sg1). Mycobacterium avium, Mycobacterium intracellulare,
and Mycobacterium abscessus are three leading species
associated with pulmonary NTM disease. The estimated rates of these diseases are
increasing in the United States, and the cost of treatment is high. Therefore, a
national assessment of water disinfection efficacy for these pathogens was
needed. The disinfectant type and total chlorine residual (TClR) were
investigated to understand their influence on the detection and concentrations
of the five pathogens in potable water. Samples (n=358) were collected
from point-of-use taps (cold or hot) from locations across the United States
served by public water utilities that disinfected with chlorine or chloramine.
The bacteria were detected and quantified using specific primer and probe
quantitative-PCR (qPCR) methods. The total chlorine residual was measured
spectrophotometrically. Chlorine was the more potent disinfectant for
controlling the three mycobacterial species. Chloramine was effective at
controlling L. pneumophila and Sg1. Plotting the TClR
associated with positive microbial detection showed that an upward TClR
adjustment could reduce the bacterial count in chlorinated water but was not as
effective for chloramine. Each species of bacteria responded differently to the
disinfection type, concentration, and temperature. There was no unifying
condition among the water characteristics studied that achieved microbial
control for all. This information will help guide disinfectant decisions aimed
at reducing occurrences of these pathogens at consumer taps and as related to
the disinfectant type and TClR. IMPORTANCE: The primary purpose of tap
water disinfection is to control the presence of microbes. This study evaluated
the role of disinfectant choice on the presence at the tap of L.
pneumophila, its Sg1 serogroup, and three species of mycobacteria in tap
water samples collected at points of human exposure at locations across the
United States. The study demonstrates that microbial survival varies based on
the microbial species, disinfectant, and TClR.
Girolamini L, Dormi A, Pellati T,
Somaroli P, Montanari D, Costa A, Savelli F, Martelli A, Grottola A, Fregni
Serpini G, Cristino S.
Department of Biological, Geological, and
Environmental Sciences, BiGeA, University of Bologna, Bologna, Italy. sandra.cristino@unibo.it
Pathogens 2019 Oct;8(4):209.
Abstract:
Legionella surveillance is an important issue in public health,
linked to the severity of disease and the difficulty associated with eradicating
this bacterium from the water environment. Different treatments are suggested to
reduce Legionella risk, however long-term studies of their
efficiency are lacking. This study focused on the activity of a new formulation
of hydrogen peroxide and silver salts, WTP828, in the hospital hot water network
(HWN) to contain Legionella contamination during two years of
treatment. The effectiveness of WTP828 was tested measuring physical-chemical
and microbiological parameters such as Legionella, Pseudomonas
aeruginosa (P. aeruginosa), and a heterotopic plate count (HPC)
at 36 °C. Legionella isolates were identified by serotyping
and genotyping. WTP 828 induced a reduction in Legionella-positive
sites (60% to 36%) and contamination levels (2.12 to 1.7 log10 CFU/L),
with isolates belonging to L. pneumophila SG1 (ST1 and ST104), L.
anisa and L. rubrilucens widely distributed in HWN. No
relevant contamination was found for other parameters tested. The long-term
effect of WTP828 on Legionella containment suggest the easy and
safe application of this disinfectant, that combined with knowledge of building
characteristics, an adequate environmental monitoring and risk assessment plan,
become the key elements in preventing Legionella contamination
and exposure.
Antimicrobial Effect of Visible
Light-Photoinactivation of Legionella rubrilucens by
Irradiation at 450, 470, and 620 nm
Schmid J, Hoenes
K, Vatter P, Hessling M.
Ulm University of Applied Sciences, Department of
Medical Engineering and Mechatronics, Ulm, Germany. martin.hessling@thu.de
Antibiotics (Basel) 2019 Oct;8(4):187.
Abstract: Despite the high
number of Legionella infections, there are currently no convincing
preventive measures. Photoinactivation with visible light is a promising new
approach and the photoinactivation sensitivity properties of planktonic Legionella
rubrilucens to 450, 470, and 620 nm irradiation were thus investigated
and compared to existing 405 nm inactivation data for obtaining information on
responsible endogenous photosensitizers. Legionella were streaked on agar
plates and irradiated with different doses by light emitting diodes (LEDs) of
different visible wavelengths. When irradiating bacterial samples with blue
light of 450 nm, a 5-log reduction could be achieved by applying a dose of 300 J
cm-2, whereas at 470 nm, a comparable reduction required about 500 J
cm-2. For red irradiation at 620 nm, no inactivation could be
observed, even at 500 J cm-2. The declining photoinactivation
sensitivity with an increasing wavelength is consistent with the assumption of
porphyrins and flavins being among the relevant photosensitizers. These results
were obtained for L. rubrilucens, but there is reason to believe
that its inactivation behavior is similar to that of pathogenic legionella
species. Therefore, this photoinactivation might lead to new future concepts for
legionella reduction and prevention in technical applications or even on or
inside the human body.
Buse HY, J Morris B,
Struewing IT, Szabo JG.
U.S. Environmental Protection Agency,
Office of Research and Development, National Homeland Security Research Center,
Cincinnati, Ohio, USA. buse.helen@epa.gov
Appl Environ Microbiol 2019;85(7):e02956-18.
Abstract:
Building water systems promote the regrowth and survival of opportunistic
pathogens, such as Legionella pneumophila, especially within
biofilms, where most drinking water microbes reside. However, compared to their
planktonic form, disinfection efficacy for the biofilm-associated forms of
water-based pathogens is unclear. The aim of this study was to determine the
effectiveness of free chlorine and monochloramine in the inactivation of
biofilm-associated L. pneumophila strain Philadelphia-1
serogroup 1 (LpP1s1). Mature (1.5- to 2-year-old) drinking water biofilms were
developed on copper (Cu) and polyvinyl chloride (PVC) slides within biofilm
annular reactors, then colonized with LpP1s1 at approximately 4 log10 CFU
cm-2 and exposed to 2 mg liter-1 of free
chlorine or monochloramine. Ct (disinfectant concentration ×
time, expressed as mg min liter-1) inactivation values for 2-, 3-,
and 4-log10 reductions of planktonic and biofilm LpP1s1 were
determined. For planktonic LpP1s1, free chlorine was more effective at
inactivation than was monochloramine treatment, and for biofilm associated
LpP1s1, monochloramine was more effective on Cu biofilms while free chlorine was
more effective on PVC biofilms. In contrast to monochloramine, free chlorine
treatment of Cu and PVC biofilms, negatively impacted LpP1s1 16S rRNA gene
transcript levels and may act synergistically with Cu surfaces to further reduce
transcript levels. Moreover, LpP1s1 cells shed from biofilms into the bulk water
were more resistant to disinfection than were prepared planktonic LpP1s1 cells.
Results from this study indicate that biofilm association, disinfectant type,
and substratum play an important role in the survival of Legionella
pneumophila in building water systems. IMPORTANCE: Microbial
regrowth within building water systems are promoted by water stagnation, low
disinfectant residual, high surface-to-volume ratio, amenable growth
temperatures, and colonization of drinking water biofilms. Moreover, biofilms
provide protection from environmental stresses, access to higher levels of
nutrients, and opportunities for symbiotic interactions with other microbes.
Disinfectant efficacy information is historically based on inactivation of
pathogens in their planktonic, free-floating forms. However, due to the
ecological importance of drinking water biofilms for pathogen survival, this
study evaluated the efficacy of two common disinfectants, free chlorine and
monochloramine, on Legionella pneumophila colonizing mature,
drinking water biofilms established on copper and PVC surfaces. Results showed
that inactivation was dependent on the disinfectant type and biofilm substratum.
Overall, this, and other related research, will provide a better understanding
of Legionella ecological stability and survival and aid policy
makers in the management of exposure risks to water-based pathogens within
building water systems.
Cloutman-Green E, Barbosa VL, Jimenez D, Wong D, Dunn H, Needham B, Ciric L, Hartley JC.
Department
of Microbiology, Virology, and Infection Prevention Control, Great Ormond Street
Hospital NHS Foundation Trust, London, United Kingdom. elaine.cloutman-green@gosh.nhs.uk
Am J Infect Control 2019 Jul;47(7):761-766.
Abstract:
Background: Hospital-acquired
Legionnaires' disease is associated with the presence of Legionella
pneumophila in hospital water systems. In the United Kingdom, the Department
of Health recommends maintaining hot water temperatures >55°C and cold water
temperatures <20°C at the point of delivery to prevent proliferation of L.
pneumophila in water systems. In this study, we evaluated the efficacy of
copper and silver ionization to control L. pneumophila at deliberately
reduced hot water temperatures (43°C) within a newly installed water system in
a new building linked to a large health care facility in the United Kingdom. Methods: One
thousand, five hundred ninety-eight water samples were collected between
September 2011 and June 2017. Samples were tested using accredited methods for L.
pneumophila, copper and silver ion levels, and total viable counts. Energy
consumption and water usage data were also collected to permit carbon emission
calculations. Results: The
results of 1,598 routine samples from September 2011 to June 2017, and the
recordings of temperatures at outlets in this facility, demonstrated effective
(100%) L. pneumophila control throughout the study period with an average
hot water temperature of 42°C. The energy savings and reduction of carbon
emissions were calculated to amount to 33% and 24%, respectively, compared to an
equivalent temperature-controlled system. Water system management interventions
were required to achieve consistently adequate levels of copper and silver
across outlets. Conclusions: This
study demonstrated that it is possible to control L pneumophila
independent of temperature when copper and silver ionization is introduced into
a new building in conjunction with an appropriately managed water system.
Vincenti S,
de Waure C, Raponi M, Teleman AA, Boninti F, Bruno S, Boccia S, Damiani
G, Laurenti P.
Fondazione Policlinico Universitario A. Gemelli IRCCS, Roma,
Italy. matteo.raponi@guest.policlinicogemelli.it
Sci Total Environ 2019 Mar;657:248-253.
Abstract:
The prevention of Legionella colonization of water systems is one of the
goals of hospital management. Among chemical disinfection methods, chlorine
dioxide (ClO2) has been largely used to control Legionella spp.
in water systems. We performed a retrospective study to analyse data deriving
from the surveillance plan of the water system in a large academic hospital in
Rome (Italy) during the period August 2011 and August 2018. We collected the
data deriving from the routine water samples used to monitor Legionella
spp. colonization. Data from the water samples collected from 163 selected
sampling points (hot water tanks, the return loop and distal outlets) was
analysed using a life table analysis in order to investigate the duration of the
effectiveness of the ClO2 method in eradicating Legionella
spp. The colonization of the water sample by Legionella spp. was
considered as the outcome. Our results show that in 81,59% of the sampling
points Legionella spp. were never detected at four years of follow up.
Chemical and physical characteristics of the water were also compared between
the samples which were positive for Legionella spp. and those which were
not. No association was found between these factors. The knowledge of the
duration over time of the effectiveness of the ClO2 disinfection
method could support decision-making processes in the framework of Risk
Management activities in hospitals. Future studies could also be conducted in
hospitals to compare the long-term cost-effectiveness of different Legionella
spp. colonization prevention methods.
Gavaldà L, Garcia-Nuñez M, Quero S, Gutierrez-Milla C,
Sabrià M.
Department
of Preventive Medicine-Hospital Hygiene, Hospital Universitari de
Bellvitge-IDIBELL, Barcelona, Spain. lgavalda@bellvitgehospital.cat
Water Res 2019 Feb;149:460-466.
Abstract:
Although measures to minimize Legionella colonization in sanitary hot
water installations are well established, there is little evidence of their
long-term effectiveness in hospital buildings. During an 8-year period, hot
water in a large hospital building was sampled monthly in areas with suitable
dimensioning and recirculation and in areas with dead legs and low-use taps. In
the former areas, the percentage of Legionella-negative samples was 83.2%
when the temperature was ≥55°C, 64.9% when between 50.1°C and 54.0°C,
and 51.6% when ≤50°C (p for trend <0.001). In the highest temperature
group, no samples with ≥103 cfu/L were observed. In poorly
designed areas, only 44.7% of samples were negative, and 28.9% presented
≥103 cfu/L although reaching 55°C. In these areas,
multivariate analysis showed that if hot water supplies were not used daily, the
risk of Legionella colonization was greater than two-fold (odds ratio:
2.84; 95% confidence interval: 1.26-6.41), and the risk of finding Legionella
concentrations ≥103 cfu/L was more than three-fold (odds
ratio: 3.18; 95% confidence interval: 1.36-7.46), regardless the temperature.
These findings indicate that the effectiveness of maintaining sanitary hot water
at a minimum temperature of 55°C is significantly better than that at 50°C for
the environmental control of Legionella but only in installations with
suitable dimensioning and recirculation. In installations that do not meet these
conditions, high temperatures alone result in insufficient control.
Oh
Y, Noga R, Shanov V, Ryu H, Chandra H, Yadav B,
Yadav J, Chae S.
Department
of Chemical and Environmental Engineering, University of Cincinnati, Cincinnati,
OH 45221, U.S.A. chaesg@ucmail.uc.edu
Chem Eng J 2019;366:21-26.
Abstract:
Despite municipal chlorination and secondary disinfection, opportunistic
waterborne pathogens (e.g., Legionella spp.) persist in public
and private water distribution systems. As a potential source of
healthcare-acquired infections, this warrants development of novel pathogen
removal and inactivation systems. In this study, electrically heatable carbon
nanotube (CNT) point-of-use (POU) filters have been designed to remove and
inactivate Legionella pneumophila in water.
The CNT/polymer composite membranes
effectively removed Legionella (>99.99%) (i.e., below
detection limit) and were able to inactive them on the membrane surface at 100%
efficiency within 60 s using ohmic heating at 20 V. The novel POU filters could
be used as a final barrier to provide efficient rejection of pathogens and
thereby simultaneously eliminate microorganisms in public and private water
supplies.
Bonetta S, Pignata C, Bonetta S, Meucci L, Giacosa D, Marino E,
Gorrasi I, Gilli G, Carraro E.
Department of Public Health and
Pediatrics, University of Torino, Torino, Italy. sara.bonetta@unito.it
Chemosphere
2018 Nov;210:550-556.
Abstract: Disinfection
of hot water systems is critical for reducing Legionnaires' disease in high-risk
buildings. The use of neutral electrolysed oxidising water (NEOW) is a promising
method for the control of microorganisms in hot water systems. However,
full-scale evaluations of the efficacy of NEOW devices to control Legionella
pneumophila are currently lacking. The aim of this study was to assess the
effectiveness of a NEOW device in reducing L. pneumophila in a hotel
water network. Water samples (n=67) were collected from different sites of a
hotel distribution system before and after the installation of the NEOW device
at the 1st, 4th, 8th and 12th week. Detection of L. pneumophila was
performed comparing culture, qPCR and PMA-qPCR methods. Total bacterial counts
(22°C and 37°C), Pseudomonas spp. and physico-chemical parameters were
also monitored. The NEOW treatment resulted in a reduction of the amount of L.
pneumophila positive samples (-32%) and of the number of heavily
contaminated points (>104 CFU/L and >103 CFU/L)
(-100% and -96%, respectively). Treatment maintained L. pneumophila at
low levels (<102 CFU/L), which do not require specific
intervention measures. The effectiveness of the disinfection system was also
confirmed by PMA-qPCR (p<0.001). The use of PMA resulted in a signal decrease
in almost all samples upon the disinfection treatment. The NEOW disinfection
device appears to be a promising approach to reduce the colonisation of hot
water systems by L. pneumophila; however, further investigations are
needed to ascertain its efficiency over longer time periods.
De Battisti A, Formaglio P, Ferro S, Al Aukidy M, Verlicchi P.
Department
of Engineering, University of Ferrara, Ferrara, Italy. paola.verlicchi@unife.it
Chemosphere 2018 Sep;207:101-109.
Abstract:
Lab-scale experiments using real groundwater were carried out using the CabECO® reactor
system in order to evaluate its suitability for producing safe water, acceptable
for civil purposes. Trials were carried out in discontinuous and in continuous
mode, analyzing the influence of electrical and hydraulic process parameters on
the quality of treated water. The use of highly boron-doped diamond electrodes
in the reactor allowed the electrosynthesis of considerable amounts of ozone.
Because of the relatively high amount of chloride in the groundwater samples, a
mixture of HOCl/ClO- was also synthesized. Somewhat unexpectedly,
the increase in the current density in the explored range 100-1000 A m-2 was
accompanied by an increase in the faradaic yield of the electrosynthesis of
oxidants, which was more pronounced for ozone than for free chlorine. As
reported in literature, the main radical intermediate in the relevant reactions
is OH, which can lead to different oxidation products, namely ozone and HOCl/ClO-.
The electrolytic treatment also caused a decrease in the concentration of minor
components, including NH4+ and Br-. Other
byproducts were ClO3- and ClO4-,
although their concentration levels were low. Moreover, due to alkali formation
at the cathode surface, the precipitation of calcium and magnesium carbonates
was also observed. In addition, the experimental investigation showed that even Pseudomonas
aeruginosa and Legionella could be completely removed in the treated
stream, due to the unique capacity of the reactor to synthesize biocidal agents
like ozone, HOCl/ClO-, and chloramines. These effects were
particularly evident during batch experiments.
Coniglio MA, Ferrante M, Yassin MH.
Legionella Reference Laboratory,
Department of Medical, Surgical Sciences and Advanced Technologies "G.F.
Ingrassia", University of Catania, Catania, Italy. ma.coniglio@unict.it
Int J Environ Res Public Health 2018 Jul;15(8):1594.
Abstract:
The purpose of this study is to report the experience of the implementation and
application of a 3-year Water Safety Plan (WSP) together with the secondary
disinfection of water by monochloramine to control and prevent
healthcare-associated legionellosis in an Italian hospital strongly colonized by Legionella.
Risk assessment was carried out by the WSP team. The main critical control
points focused on in developing the WSP for the control of Legionella was
the water distribution system. A sampling plan for the detection of Legionella was
implemented. A widespread contamination of the hot water distribution system by L.
pneumophila sg5 was found. Results after 3 years of the continuous
disinfection of hot water with monochloramine indicate the eradication of Legionella.
The implementation and application of a WSP in a hospital, together with the
disinfection of the water distribution system with monochloramine, can be
effective in controlling the growth of Legionella and in
preventing nosocomial legionellosis.
Waak MB,
LaPara TM, Hallé C, Hozalski RM.
Department
of Civil, Environmental, and Geo-Engineering, University of Minnesota,
Minneapolis, Minnesota, USA. hozalski@umn.edu
Environ Sci Technol 2018 Jul;52(14):7630-7639.
Abstract:
The maintenance of a chlorine or chloramine residual to suppress waterborne
pathogens in drinking water distribution systems is common practice in the
United States but less common in Europe. In this study, we investigated the
occurrence of Bacteria and Legionella spp. in water-main biofilms and tap
water from a chloraminated distribution system in the United States and a system
in Norway with no residual using real-time quantitative polymerase chain
reaction (qPCR). Despite generally higher temperatures and assimilable organic
carbon levels in the chloraminated system, total Bacteria and Legionella
spp. were significantly lower in water-main biofilms and tap water of that
system (p<0.05). Legionella spp. were not detected in the biofilms of
the chloraminated system (0 of 35 samples) but were frequently detected in
biofilms from the no-residual system (10 of 23 samples; maximum concentration =
7.8×104 gene copies cm-2). This investigation
suggests water-main biofilms may serve as a source of Legionella for tap
water and premise plumbing systems, and residual chloramine may aid in reducing
their abundance.
Li J, LiX,
Li,
Tao T
School of
Environmental Science and Engineering, Zhejiang Gongshang University, Zhejiang,
Hangzhou, China. lijun681116@163.com
Environ
Sci Pollut Res Int 2018 Apr;25(10):9697-9707.
Abstract:
The results show that ozone concentration Apr determination using
ultraviolet spectrophotometry (UV-2450) at 258 nm is easier than using indigo
method at 600 nm. A strong linear relationship was found between purge time and
O3 concentration in deionized water. Ozone concentration can be
predicted in deionized water. A higher O3 flow rate or lower
temperature led to a higher O3 concentration. Ozone
concentration was stable in 60 min, so that ozone self-decomposition could be
ignored at ozone concentrations below 0.4 mg L-1. A higher
temperature led to a higher inactivation efficiency and rate, and that a lower
temperature led to a lower ozone decay rate and inactivation efficiency even if
ozone solubility increased when temperature decreased. The fastest inactivation
rate occurred before c0t = 165 μg
L-1 s, but the inactivation rate decreased after c0t
= 165 μg L-1 s with tail phenomena. The tail phenomena were
clearly observed and may be caused by oxidization of lipopolysaccharides (LPS),
cell membrane, etc. The activation energy Ea =55,404±0.3 J mol-1 were
obtained for Legionella inactivation with ozone in deionized water. Ozone
maximum decay rate was positively proportional to COD concentration. COD
impacted on ozone concentration seriously. Higher COD concentration resulted in
higher ozone decay rate. COD could result in ozone concentration decrement
rapidly to a steady value in 5 s. Higher initial ozone concentration resulted in
higher germ inactivation rate. Higher initial COD concentration resulted in
lower Legionella inactivation efficiency. COD was easier to react with ozone
than Legionella. The relationship among the initial COD concentrations
COD0, the initial O3 concentration c0, and
the O3 contact time t necessary for a 99.999% reduction of Legionella
in wastewater can be expressed in some equations. O3 disinfection
time t necessary for a 99.999% reduction of Legionella can be predicted
by Eqs. (10) and (11).
Stüken A,
Haverkamp THA, Dirven HAAM, Gilfillan GD, Leithaug M, Lund V.
Dept.
Zoonotic, Food and Waterborne Infections, Norwegian Institute of Public Health,
Oslo, Norway. anke.stuken@fhi.no
Environ Sci Technol 2018 Mar;52(6):3354-3364.
Abstract:
Copper-silver ionization (CSI) is an in-house water disinfection method
primarily installed to eradicate Legionella bacteria from drinking water
distribution systems (DWDS). Its effect on the abundance of culturable Legionella
and Legionella infections has been documented in several studies. However,
the effect of CSI on other bacteria in DWDS is largely unknown. To investigate
these effects, we characterized drinking water and biofilm communities in a
hospital using CSI, in a neighboring building without CSI, and in treated
drinking water at the local water treatment plant. We used 16S rDNA amplicon
sequencing and Legionella culturing. The sequencing results revealed
three distinct water groups: (1) cold-water samples (no CSI), (2) warm-water
samples at the research institute (no CSI), and (3) warm-water samples at the
hospital (after CSI; ANOSIM, p<0.001). Differences between the biofilm
communities exposed and not exposed to CSI were less clear (ANOSIM, p=0.022). No
Legionella were cultured, but limited numbers of Legionella
sequences were recovered from all 25 water samples (0.2-1.4% relative abundance).
The clustering pattern indicated local selection of Legionella types (Kruskal-Wallis,
p<0.001). Furthermore, one unclassified Betaproteobacteria OTU was highly
enriched in CSI-treated warm water samples at the hospital (Kruskal-Wallis,
p<0.001).
Rattanakul, Oguma
K.
Research Center for Advanced Science and
Technology, The University of Tokyo, Tokyo, Japan. oguma@env.t.u-tokyo.ac.jp
Water Res 2018
Mar;130:31-37.
Abstract:
To demonstrate the effectiveness of UV light-emitting diodes (UV-LEDs) to
disinfect water, UV-LEDs at peak emission wavelengths of 265, 280, and 300 nm
were adopted to inactivate pathogenic species, including Pseudomonas aeruginosa
and Legionella pneumophila, and surrogate species, including Escherichia coli,
Bacillus subtilis spores, and bacteriophage Qβ in water, compared to conventional low-pressure UV
lamp emitting at 254 nm. The inactivation profiles of each species showed either
a linear or sigmoidal survival curve, which both fit well with the Geeraerd's
model. Based on the inactivation rate constant, the 265-nm UV-LED showed most
effective fluence, except for with E. coli which showed similar inactivation
rates at 265 and 254 nm. Electrical energy consumption required for 3-log10 inactivation
(EE,3) was lowest for the 280-nm UV-LED for all microbial species
tested. Taken together, the findings of this study determined the inactivation
profiles and kinetics of both pathogenic bacteria and surrogate species under
UV-LED exposure at different wavelengths. We also demonstrated that not only
inactivation rate constants, but also energy efficiency should be considered
when selecting an emission wavelength for UV-LEDs.
Ji
P, Rhoads WJ
Edwards MA
Pruden A.
Department of Civil and Environmental
Engineering, Virginia Tech, Blacksburg, VA, USA. apruden@vt.edu.
Microbiome
2018 Feb;6(1):30.
Abstract:
Background: Heat
shock is a potential control strategy for Legionella pneumophila in hot
water plumbing systems. However, it is not consistently effective, with little
understanding of its influence on the broader plumbing microbiome. Here, we
employed a lab-scale recirculating hot water plumbing rig to compare the pre-
and post-"heat shock" (i.e., 40 → 60 →
40°C) microbiota at distal taps. In addition, we used a second plumbing rig to
represent a well-managed system at 60°C and conducted a "control"
sampling at 60°C, subsequently reducing the temperature to 40°C to observe the
effects on Legionella and the microbiota under a simulated "thermal
disruption" scenario. Results: According
to 16S rRNA gene amplicon sequencing, in the heat shock scenario, there was no
significant difference or statistically significant, but small, difference in
the microbial community composition at the distal taps pre- versus post-heat
shock (both biofilm and water; weighted and unweighted UniFrac distance matrices).
While heat shock did lead to decreased total bacteria numbers at distal taps, it
did not measurably alter the richness or evenness of the microbiota.
Quantitative PCR measurements demonstrated that L. pneumophila relative
abundance at distal taps also was not significantly different at 2-month
post-heat shock relative to the pre-heat shock condition, while relative
abundance of Vermamoeba vermiformis, a known Legionella host, did
increase. In the thermal disruption scenario, relative abundance of planktonic L.
pneumophila (quantitative PCR data) increased to levels comparable to those
observed in the heat shock scenario within 2 months of switching long-term
operation at 60 to 40°C. Overall, water use frequency and water heater
temperature set point exhibited a stronger effect than one-time heat shock on
the microbial composition and Legionella levels at distal taps. Conclusions: While heat shock may be
effective for instantaneous Legionella control and reduction in total
bacteria numbers, water heater temperature set point and water use frequency are
more promising factors for long-term Legionella and microbial community
control, illustrating the importance of maintaining consistent elevated
temperatures in the system relative to short-term heat shock.
Casini B, Baggiani A, Totaro M,
Mansi A, Costa AL, Aquino
F, Miccoli M, Valentini P,
Bruschi F, Lopalco PL,
Privitera G.
Department of Translational Research,
N.T.M.S., University of Pisa, Pisa, Italy. beatrice.casini@med.unipi.it
J Hosp Infect 2018 Jan;98(1):46-52.
Abstract:
Background: Prevention
of legionellosis remains a critical issue in healthcare settings where
monochloramine (MC) disinfection was recently introduced as an alternative to
chlorine dioxide in controlling Legionella spp. contamination of the
hospital water network. Continuous treatments with low MC doses in some
instances have induced a viable but non-culturable state (VBNC) of Legionella
spp. Aim: To investigate the occurrence of
such dormant cells during a long period of continuous MC treatment. Methods: Between
November 2010 and April 2015, 162 water and biofilm samples were collected, and Legionella
spp. isolated in accordance with standard procedures. In sampling sites where MC
was <1.5 mg/L, VBNC cells were investigated by ethidium monoazide bromide
(EMA)-real-time polymerase chain reaction (qPCR) and 'resuscitation' test into Acanthamoeba
polyphaga CCAP 1501/18. According to the Health Protection Agency protocol,
free-living protozoa were researched in 60 five-litre water samples. Findings: In all,
136 out of 156 (87.2%) of the samples taken from sites previously positive for L.
pneumophila ST269 were negative by culture, but only 47 (34.5%) negative by
qPCR. Although no positive results were obtained by EMA-qPCR, four out of 22
samples associated with MC concentration of 1.3± 0.5 mg/L showed VBNC
legionella resuscitation. The presence of the amoeba A. polyphaga in the
hospital water network was demonstrated. Conclusion: Our
study is the first report evidencing the emergence of VNBC legionella during a
long period of continuous MC treatment of a hospital water network, highlighting
the importance of keeping an appropriate and uninterrupted MC dosage to ensure
the control of legionella colonization in hospital water supplies.
Totaro M
Valentini P Costa AL,
Giorgi S Casini B
Baggiani A.
Department
of Translational Research and New Technologies in Medicine and Surgery,
University of Pisa, Pisa, Italy. angelo.baggiani@med.unipi.it
J Hosp Infect 2018 Jan;98(1):60-63.
Abstract: In hospital water systems legionellae may be
resistant to disinfectants in pipework, which is a problem particularly in areas
where there is low flow or stagnation of water. We evaluated legionella
colonization of a water network of an Italian hospital after time flow taps (TFTs)
installation in proximity to dead legs. The water volume flushed was 64 L/day
from May 2016, and 192 L/day from December 2016. Before TFTs installation, Legionella
pneumophila sg2-14 was detected in all points (4×104±3.1×104 cfu/L).
All sites remained positive (2.9×104±1.9×104 cfu/L)
through November 2016. From December 2016 legionella persisted in one point only
(2×102 to 6.8×103 cfu/L). TFTs with chemical
disinfection may reduce legionella colonization associated with dead legs.
Li Q, Yu S, Li
L Liu
G Gu
Z, Liu M, Liu Z, Ye
Y, Xia Q, Ren L.
State
Key Laboratory of Pollution Control and Resource Reuse, College of Environmental
Science and Engineering, Tongji University, Shanghai, China. ysl@tongji.edu.cn
Front Microbiol 2017 Dec;8:2465.
Abstract: Bacteria play an important role in water
purification in drinking water treatment systems. On one hand, bacteria present
in the untreated water may help in its purification through biodegradation of
the contaminants. On the other hand, some bacteria may be human pathogens and
pose a threat to consumers. The present study investigated bacterial communities
using Illumina MiSeq sequencing of 16S rRNA genes and their functions were
predicted using PICRUSt in a treatment system, including the biofilms on sand
filters and biological activated carbon (BAC) filters, in 4 months. In addition,
quantitative analyses of specific bacterial populations were performed by
real-time quantitative polymerase chain reaction (qPCR). The bacterial community
composition of post-ozonation effluent, BAC effluent and disinfected water
varied with sampling time. However, the bacterial community structures at other
treatment steps were relatively stable, despite great variations of source water
quality, resulting in stable treatment performance. Illumina MiSeq sequencing
illustrated that Proteobacteria was dominant bacterial phylum.
Chlorine disinfection significantly influenced the microbial community structure,
while other treatment processes were synergetic. Bacterial communities in water
and biofilms were distinct, and distinctions of bacterial communities also
existed between different biofilms. By contrast, the functional composition of
biofilms on different filters were similar. Some functional genes related to
pollutant degradation were found widely distributed throughout the treatment
processes. The distributions of Mycobacterium spp. and Legionella spp.
in water and biofilms were revealed by real-time quantitative polymerase chain
reaction (qPCR). Most bacteria, including potential pathogens, could be
effectively removed by chlorine disinfection. However, some bacteria presented
great resistance to chlorine. qPCRs showed that Mycobacterium spp.
could not be effectively removed by chlorine. These resistant bacteria and,
especially potential pathogens should receive more attention. Redundancy
analysis (RDA)
showed that turbidity, ammonia nitrogen and total organic carbon (TOC) exerted
significant effects on community profiles. Overall, this study provides insight
into variations of microbial communities in the treatment processes and aids the
optimization of drinking water treatment plant design and operation for public
health.
Whiley H, Bentham R, Brown MH.
College of Science and Engineering,
Flinders University, Bedford, Australia. harriet.whiley@flinders.edu.au
Front
Microbiol 2017 Jul;8:1330.
Abstract:
Legionella is an opportunistic waterborne pathogen of increasing
public health significance. Pasteurization, otherwise known as super-heat and
flush (increasing water temperature to above 70°C and flushing all outlets),
has been identified as an important mechanism for the disinfection of Legionella in
manufactured water systems. However, several studies have reported that this
procedure was ineffective at remediating water distribution systems as Legionella was
able to maintain long term persistent contamination. Up to 25% of L.
pneumophila cells survived heat treatment of 70°C, but all of these
were in a viable but non-culturable state. This demonstrates the limitations of
the culture method of Legionella detection currently used to
evaluate disinfection protocols. In addition, it has been demonstrated that
pasteurization and nutrient starvation can select for thermal tolerant strains,
where L. pneumophila was consistently identified as having
greater thermal tolerance compared to other Legionella species.
This review demonstrates that further research is needed to investigate the
effectiveness of pasteurization as a disinfection method. In particular, it
focuses on the potential for pasteurization to select for thermal tolerant L.
pneumophila strains which, as the primary causative agent of
Legionnaires disease, have greater public health significance compared to other Legionella species.
Rhoads WJ, Pruden A, Edwards MA.
Department
of Civil and Environmental Engineering, Virginia Polytechnic Institute and State
University, Blacksburg, Virginia, USA. wrhoads@vt.edu
Environ Sci Technol 2017 Jun;51(12):7065-7075.
Abstract:
Complexities associated with drinking water plumbing systems can result in
undesirable interactions among plumbing components that undermine engineering
controls for opportunistic pathogens (OPs). In this study, we examine the
effects of plumbing system materials and two commonly applied disinfectants,
copper and chloramines, on water chemistry and the growth of Legionella
and mycobacteria across a transect of bench- and pilot-scale hot water
experiments carried out with the same municipal water supply. We discovered that
copper released from corrosion of plumbing materials can initiate evolution of
>1100 times more hydrogen (H2) from water heater sacrificial anode
rods than does presence of copper dosed as soluble cupric ions. H2 is
a favorable electron donor for autotrophs and causes fixation of organic carbon
that could serve as a nutrient for OPs. Dosed cupric ions acted as a
disinfectant in stratified stagnant pipes, inhibiting culturable Legionella and
biofilm formation, but promoted Legionella growth in pipes subject to
convective mixing. This difference was presumably due to continuous delivery of
nutrients to biofilm on the pipes under convective mixing conditions.
Chloramines eliminated culturable Legionella and prevented L.
pneumophila from recolonizing biofilms, but M. avium gene numbers
increased by 0.14-0.76 logs in the bulk water and were unaffected in the biofilm.
This study provides practical confirmation of past discrepancies in the
literature regarding the variable effects of copper on Legionella growth
and confirms prior reports of trade-offs between Legionella and
mycobacteria if chloramines are applied as secondary disinfectant residual.
Zanacic E,
McMartin DW, Stavrinides J.
Faculty of Engineering and Applied
Science, University of Regina, Regina, Canada. dena.mcmartin@uregina.ca
Can J Microbiol 2017 Jun;63(6):546-558.
Abstract:
Rural communities rely on surface water reservoirs for potable water. Effective
removal of chemical contaminants and bacterial pathogens from these reservoirs
requires an understanding of the bacterial community diversity that is present.
In this study, we carried out a 16S rRNA-based profiling approach to describe
the bacterial consortia in the raw surface water entering the water treatment
plants of 2 rural communities. Our results show that source water is dominated
by the Proteobacteria, Bacteroidetes, and Cyanobacteria, with some evidence of
seasonal effects altering the predominant groups at each location. A subsequent
community analysis of transects of a biological carbon filter in the water
treatment plant revealed a significant increase in the proportion of
Proteobacteria, Acidobacteria, Planctomycetes, and Nitrospirae relative to raw
water. Also, very few enteric coliforms were identified in either the source
water or within the filter, although Mycobacterium was of high abundance
and was found throughout the filter along with Aeromonas, Legionella,
and Pseudomonas. This study provides valuable insight into bacterial
community composition within drinking water treatment facilities, and the
importance of implementing appropriate disinfection practices to ensure safe
potable water for rural communities.
Schmid J, Hoenes
K, Rath M, Vatter P, Hessling M.
Ulm University of Applied Sciences, Ulm,
Germany. hessling@hs-ulm.de
GMS Hyg Infect Control 2017 Apr;12:Doc06.
Abstract:
Background: Despite the great health significance of Legionella,
there is only little information on their UV sensitivity. Besides Legionella
pneumophila only L. longbeachae has been investigated
so far. Methods: In this study L. rubrilucens has
been spread on buffered charcoal yeast extract agar and irradiated with the 254
nm UV-C emission of a mercury vapor lamp. The disinfection success is measured
by colony counting after incubation and comparison of the number of colonies on
irradiated and unirradiated reference agar plates. Results: The
average log-reduction dose is 1.08 mJ/cm2 for free L.
rubrilucens, which is at the lower end of the so far published Legionella
log-reduction values, but all three Legionella species show
similar UV-C sensitivities. Conclusion: The log-reduction dose of
legionellae in amoebae has not been investigated, but with the observed high
UV-C sensitivity for free Legionella, the idea of a future
point-of-use disinfection by small UV-C LEDs in water-taps or shower heads
appears to be realistic, even if legionellae are more resistant in amoebae.
Casini B,
Aquino F, Totaro M, Miccoli M, Galli I, Manfredini L, Giustarini C, Costa AL,
Tuvo B, Valentini P, Privitera G, Baggiani A.
Department Translational Research,
N.T.M.S., University of Pisa, Pisa, Italy. beatrice.casini@med.unipi.it
Pathogens 2017 Apr;6(2):15.
Abstract:
Objectives: To
evaluate the effectiveness of hydrogen peroxide (HP) use as a disinfectant in
the hospital water network for the control of Legionella spp.
colonization. Methods: Following
the detection of high levels of Legionella contamination in a
136-bed general hospital water network, an HP treatment of the hot water supply
(25 mg/L) was adopted. During a period of 34 months, the effectiveness of HP on Legionella colonization
was assessed. Legionella was isolated in accordance with
ISO-11731 and identification was carried out by sequencing of the mip gene.
Results: Before
HP treatment, L. pneumophila sg 2-15 was isolated in all sites
with a mean count of 9950±8279 cfu/L. After one-month of HP treatment, we
observed the disappearance of L. pneumophila 2-15, however
other Legionella species previously not seen were found; Legionella
pneumophila 1 was isolated in one out of four sampling sites (2000 cfu/L)
and other non-pneumophila species were present in all sites (mean
load 3000±2887 cfu/L). Starting from September 2013, HP treatment was modified
by adding food-grade polyphosphates, and in the following months, we observed a
progressive reduction of the mean load of all species (p<0.05),
resulting in substantial disappearance of Legionella colonization.
Conclusion: Hydrogen peroxide
demonstrated good efficacy in controlling Legionella. Although in
the initial phases of treatment it appeared unable to eliminate all Legionella species,
by maintaining HP levels at 25 mg/L and adding food-grade polyphosphates, a
progressive and complete control of colonization was obtained.
Schmid J, Hoenes
K, Rath M, Vatter P, Spellerberg B, Hessling M.
Ulm University of Applied Sciences, Ulm,
Germany. hessling@hs-ulm.de
Eur J Microbiol Immunol (Bp) 2017 Apr;7(2):146-149.
Abstract:
In this study, the photoinactivation of Legionella by visible
light is investigated. The success of this approach would offer new prospects
for technical water disinfection and maybe even for therapeutic measures in
cases of Legionella infections. Therefore, Legionella
rubrilucens was dispensed on buffered charcoal yeast extract medium
agar plates and illuminated with different doses of violet light generated by
405 nm light-emitting diodes (LEDs). A strong photoinactivation effect was
observed. A dose of 125 J/cm2 reduced the bacterial
concentration by more than 5 orders of magnitude compared to Legionella on
unirradiated agar plates. The necessary dose for a one log-level reduction was
about 24 J/cm2. These results were obtained for extracellular L.
rubrilucens, but other Legionella species may exhibit a
similar behavior.
Li J, Li
K, Zhou Y, Li X,
Tao T.
School of Environmental Science and
Engineering, Zhejiang Gongshang University, Zhejiang, China. lijun681116@163.com
Chemosphere 2017 Feb;168:630-637.
Abstract:
Legionella
inactivation using ozone was studied in wastewater using kinetic analysis and
modeling. The experimental results indicate that the relationship between the
ozone concentration, germ concentration, and chemical oxygen demand (COD) can be
used to predict variations in germ and COD concentrations. The ozone reaction
with COD and inactivation of Legionella occurred simultaneously, but the
reaction with COD likely occurred at a higher rate than the inactivation, as COD
is more easily oxidized by ozone than Legionella. Higher initial COD
concentrations resulted in a lower inactivation rate and higher lnN/N0.
Higher temperature led to a higher inactivation efficiency. The relationship of
the initial O3 concentration and Legionella inactivation
rate was not linear, and thus, the Ct value required for a 99.99% reduction was
not constant. The initial O3 concentration was more important
than the contact time, and a reduction of the initial O3 concentration
could not be compensated by increasing the contact time. The Ct values were
compared over a narrow range of initial concentrations; the Ct values could only
be contrasted when the initial O3 concentrations were very
similar. A higher initial O3 concentration led to a higher
inflection point value for the lnN/N0 vs C0t curve.
Energy consumption using a plasma corona was lower than when using boron-doped
diamond electrodes.
