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Sorgenti ambientali (2020 -2017)
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in evaporative cooling systems and underlying causes of associated breaches in
health and safety compliance
B, Willerton L, Smith D, Wilson L, Poran V, Helps J, McDermott P.
Health and Safety Executive, Buxton, SK17 9JN, UK.
Int J Hyg Environ Health 2020 Mar;224:113425.
Abstract: Legionella bacteria can colonise and
proliferate in water systems in the built environment and can be spread by
aerosol generation. If inhaled by a susceptible individual, this can lead to
respiratory infections such as Legionnaires' Disease (LD), or the generally
milder Pontiac fever. Evaporative cooling systems (ECS), including cooling
towers, used in industrial processes to dissipate excessive heat are prone to
contamination by Legionella. From these systems it is possible for
contaminated aerosols to be dispersed over a wide area, potentially exposing
workers on site, neighbouring workplaces or nearby members of the public.
Analysis of reported data on outbreaks of LD in Great Britain, collated for a
ten-year period, identified 44 separate legionellosis outbreaks of which seven
were attributed to ECS and were responsible for 229 infections and 10 fatalities.
This prompted an examination of health and safety inspection records which
revealed, over a five-year period, 321 enforcement actions taken against
failings in Legionella control, of which 31% were attributed to
cooling towers. Based on this evidence, an intervention programme was undertaken
by health and safety inspectors in which 1,906 sites with ECS were inspected.
During these inspections, sites were rated against four topics that are used to
demonstrate compliance with statutory requirements for Legionella control:
Risk Assessment; Written Control Scheme; Implementation of Control Scheme; and
Record Keeping. While there was compliance at the majority of sites, breaches of
the legislation were found at 625 sites (33% of those inspected), leading to 409
Improvement Notices (compelling dutyholders to make improvements to health and
safety breaches of law in a given timeframe) and 12 Prohibition Notices (compelling
dutyholders to stop work until they have remedied breaches in health and safety
law) being served at 229 sites (12.0% of those inspected). Data from the
intervention programme was analysed to identify root causes of these breaches of
legislation on Legionella control. The majority of Improvement
Notices (53%) were issued for the 'lack of effective implementation of a Written
Control Scheme', with 'Risk Assessment' and 'Written Control Scheme' both
accounting for 23%. More detailed examination showed major problems to be lack
of training; failure to maintain the cleanliness of cooling towers and the water
within them; risk assessments either being absent or not up to date, i.e., no
longer representing the risks present; and Written Control Schemes being absent
or insufficiently detailed. This provides a valuable data resource for
dutyholders, so that they can understand where they need to focus to achieve
significant improvement in legal compliance and therefore reduce the risk of LD
for employees and members of the public affected by their workplace, and
valuable data for regulators to target future interventions aimed at improving
dutyholder compliance leading to better protection of workers and members of the
Bédard É, Whyte LG, Ronholm J, Prévost M, Faucher SP.
Department of Natural Resource Sciences, Faculty of Agricultural and
Environmental Sciences, McGill University, Sainte-Anne-de-Bellevue, QC, Canada. firstname.lastname@example.org
Water Res 2020 Feb;169:115252.
Abstract: Legionnaires' disease (LD) is a severe pneumonia
caused by several species of the genus Legionella, most frequently by Legionella
pneumophila. Cooling towers are the most common source for large
community-associated outbreaks. Colonization, survival, and proliferation of L.
pneumophila in cooling towers are necessary for outbreaks to occur. These
steps are affected by the chemical and physical parameters of the cooling tower
environment. We hypothesize that the bacterial community residing in the cooling
tower could also affect the presence of L. pneumophila. A 16S rRNA gene targeted
amplicon sequencing approach was used to study the bacterial community of
cooling towers and its relationship with the Legionella spp. and L.
pneumophila communities. The results indicated that the water source shaped
the bacterial community of cooling towers. Several taxa were enriched and
positively correlated with Legionella spp. and L. pneumophila. In
contrast, Pseudomonas showed a strong negative correlation with Legionella
spp. and several other genera. Most importantly, continuous chlorine application
reduced microbial diversity and promoted the presence of Pseudomonas
creating a non-permissive environment for Legionella spp. This suggests
that disinfection strategies as well as the resident microbial population
influences the ability of Legionella spp. to colonize cooling towers.
Dyke S, Barrass I, Pollock K, Hall IM.
School of Mathematics, The
University of Manchester, Manchester, United Kingdom.
PLoS One 2019 Nov;14(11):e0224144.
Abstract: Legionnaires' disease, a form of pneumonia which
can be fatal, is transmitted via the inhalation of water droplets containing Legionella
bacteria. These droplets can be dispersed in the atmosphere several kilometers
from their source. The most common such sources are contaminated water within
cooling towers and other air-conditioning systems but other sources such as
ornamental fountains and spa pools have also caused outbreaks of the disease in
the past. There is an obvious need to locate and eliminate any such sources as
quickly as possible. Here a maximum likelihood model estimating the source of an
outbreak from case location data has been developed and implemented. Unlike
previous models, the average dose exposure sub-model is formulated using a
atmospheric dispersion model. How the uncertainty in inferred parameters can be
estimated is discussed. The model is applied to the 2012 Edinburgh Legionnaires'
van der Lugt W, Euser SM, Bruin JP, den Boer JW, Yzerman EPF.
Van der Lugt B.V., Heiligland 28A, 1821, AC, Alkmaar,
the Netherlands. Wilco@vdlugt.nl
Water Res. 2019 Sep;161:581-589.
Abstract: Previous analysis of the Dutch National
Legionella Outbreak Detection Program 2002-2012 has shown that buildings
required to maintain a Legionella control plan for their drinking water
installation are more likely to test positive for Legionella spp. Than
buildings without such a plan (38% versus 22% of samples). To clarify this
discrepancy, we analysed the results of mandatory water sample testing conducted
as part of risk assessments in 206 buildings in the Netherlands from 2011 to
2015. Of the 6171 samples analysed, 16.2% exceeded the Dutch drinking water
standard for Legionella spp. of 100 CFU/litre. In buildings with
≤50 tap points, the average percentage of samples containing ≥100
CFU/litre was 28.2%, and from buildings with >50 tap points, it was 12.2%.
Analysis of serial samples (taken every 6 months) from each building showed that
33.2% of all buildings tested positive for at least one sample every 6 months.
The overall increase was 4.4% per year. Analysis of Legionella subgroups
showed that while the majority of positive samples contained L. non-pneumophila
(96.9%), some samples did contain L. pneumophila serogroup 1 (1.0%) and
serogroups 2-14 (2.1%). Our data suggest that the Dutch mandatory risk
assessment and drinking water management plan is not sufficiently effective in
preventing the proliferation of Legionella spp. and may even contribute
to proliferation. This analysis should now be expanded to include other areas of
the Netherlands in order to understand the geographical differences that we
observed in our results, and why smaller buildings appear to be more likely to
test positive for Legionella spp.
Valciņa O, Pūle D, Malievs A, Trofimova J, Makarova S, Konvisers G, Bērziņ
A, Krūmiņa A.
Institute of Food Safety, Animal Health and Environment "BIOR",
LV-1076 Rīga, Latvia. email@example.com
Medicina (Kaunas) 2019 Aug;55(8):492.
Abstract: Background and Objectives: Legionella is
one of the most important water-related pathogens. Inside the water supply
systems and the biofilms, Legionella interact with other
bacteria and free-living amoeba (FLA). Several amoebas may serve as hosts for
bacteria in aquatic systems. This study aimed to investigate the co-occurrence
of Legionella spp. and FLA in drinking water supply systems. Materials
and Methods: A total of 268 water samples were collected from apartment
buildings, hotels, and public buildings. Detection of Legionella spp.
was performed in accordance with ISO 11731:2017 standard. Three different
polymerase chain reaction (PCR) protocols were used to identify FLA. Results: Occurrence
of Legionella varied from an average of 12.5% in cold water
samples with the most frequent occurrence observed in hot water, in areas
receiving untreated groundwater, where 54.0% of the samples were Legionella positive.
The occurrence of FLA was significantly higher. On average, 77.2% of samples
contained at least one genus of FLA and, depending on the type of sample, the
occurrence of FLA could reach 95%. In the samples collected during the study, Legionella was
always isolated along with FLA, no samples containing Legionella in
the absence of FLA were observed. Conclusions: The data
obtained in our study can help to focus on the extensive distribution, close
interaction, and long-term persistence of Legionella and FLA.
Lack of Legionella risk management plans and control procedures
may promote further spread of Legionella in water supply
systems. In addition, the high incidence of Legionella-related FLA
suggests that traditional monitoring methods may not be sufficient for Legionella control.
V, Mraz AL, López-Gálvez N, Weir MH,
Werner J, Beamer PI, Verhougstraete MP.
of Community, Environment, and Policy, Mel and Enid Zuckerman College of Public
Health, The University of Arizona, Tucson, AZ, USA. firstname.lastname@example.org
Water (Basel) 2019 Aug;11(8):1528.
Legionella pneumophila (L.
pneumophila), the causative agent of legionellosis, is an aquatic bacterium
that grows in warm water. Humans are only presented with a health risk when
aerosolized water containing L. pneumophila is inhaled. In
mining operations, aerosolized water is used as dust control and as part of the
drilling operations, a currently ignored exposure route. This study
characterized L. pneumophila concentrations in the mine's
non-potable water and the relationship between L. pneumophila and
chlorine concentrations. These concentrations informed a quantitative microbial
risk assessment (QMRA) model to estimate the infection risk to miners exposed to
aerosolized water containing L. pneumophila. Fourteen water samples
were collected from seven locations at a mine and analyzed for temperature, pH,
chlorine, and L. pneumophila serogroup. Most samples (93%)
tested positive for L. pneumophila cells. The faucet from the
sprinkler system on the adit level (entrance to the underground mine levels)
showed the highest concentration of L. pneumophila (8.35×104 MPN/L).
Disability adjusted life years (DALYs) were estimated in the QMRA model and
showed that the risk for all miners was significantly lower (p<0.0001)
with the ventilation system on than when the system was off. Our study showed
that the use of a ventilation system at the adit level of the mine reduced the
risk of infection with aerosolized L. pneumophila.
Nakagawa N, Watanabe K, Shimizu T, Watarai M.
The United Graduate School of Veterinary Science,
Yamaguchi University, Japan.
Biomed Res Int 2019
Abstract: Legionella pneumophila is known as a
human pathogen and is ubiquitous in natural and artificial aquatic environments.
Many studies have revealed the virulence traits of L. pneumophila using
clinical strains and a number of studies for characterizing environmental
strains are also reported. However, the association between the virulence and
survivability in the environment is unclear. In the present study, L.
pneumophila was isolated from environmental water sites (Ashiyu foot
spa, water fountain, and public bath), and the serogroups of isolated strains
were determined by serological tests. Isolated strains were found to belong to
serogroups SG1, SG2, SG3, SG4, SG5, SG8, SG9, and SG13. Untypeable strains were
also obtained. Isolated strains were used for intracellular growth assay in a
human monocytic cell line, THP-1. Among these strains, only an untypeable strain,
named AY3, failed to replicate in THP-1. In addition, AY3 was maintained for a
long period in an environmental water site, Ashiyu foot spa 2. Further, we
compared the characteristics of several strains isolated from Ashiyu foot spa 2
and a clinical strain, Togus-1. AY3 failed to replicate in THP-1 cells but
replicated in an amoeba model, Dictyostelium discoideum. Compared
with Togus-1, the culturable cell number of environmental strains under stress
conditions was higher. Moreover, biofilm formation was assessed, and AY3 showed
the same degree of biofilm formation as Togus-1. Biofilm formation, replication
in amoebae, and resistance against stress factors would explain the predominance
of AY3 at one environmental site. Although the mechanism underlying the
difference in the ability of AY3 to replicate in THP-1 cells or amoebae is still
unclear, AY3 may abandon the ability to replicate in THP-1 cells to survive in
one environment for a long period. Understanding the mechanisms of L.
pneumophila in replication within different hosts should help in the
control of Legionnaires' disease, but further study is necessary.
Sharaby Y, Rodríguez-Martínez S, Höfle MG, Brettar I, Halpern M.
Department of Evolutionary and Environmental Biology, Faculty of Natural
Sciences, University of Haifa, Haifa, Israel. email@example.com
Sci Total Environ 2019
Abstract: Legionella pneumophila cause human
infections via inhalation of contaminated water aerosols, resulting in severe
pneumonia. Legionella spp. prevalence was monitored in a drinking-water
distribution system (DWDS) in Northern Israel. Five points (toilet faucets and
showers) were sampled seasonally along a three years period. Toilet faucets and
shower use, both generating aerosols, are known transmission routes for this
pathogen and thus, present a potential health risk. Quantitative Microbial Risk
Assessment (QMRA) was applied in order to assess the health risks posed by Legionella
for these two exposure scenarios, while considering Legionella
seasonality. The obtained results were compared with estimated tolerable risk
levels of infection and of disease set by the USEPA and WHO. Both limits were
expressed as Disability-Adjusted Life Years index (DALY) being 1×10-4 and
1×10-6, respectively. The QMRA revealed that the annual risk levels
for both faucets and showers use exceeded the acceptable risk of infection with
an average of 5.52×10-4 and 2.37×10-3 DALY'S
per person per year, respectively. Annual risk levels were stable with no
significant differences between the three years. Risk levels varied
significantly between seasons by up to three orders of magnitude. Risk levels
were highest during summer, autumn, and lowest during winter. The highest
seasonal infection risk values were found in summer for both faucets and showers,
which corresponded to 8.09×10-4 and 2.75×10-3 DALY'S
per person per year, respectively. In conclusion, during summer and autumn there
is a significant increase of the infection risk associated with exposure to Legionella-contaminated
aerosols, in the studied water system. Public health assessment and prevention
measures should focus on these seasons.
KLG, Lut MC, Liu G, Smidt H, van der
KWR Watercycle Research Institute,
Nieuwegein, the Netherlands. Kimberly.Learbuch@kwrwater.nl
Res 2019 Jun;157:55-63.
Treatment processes, such as membrane filtration with reverse osmosis (RO), are
used to produce drinking water with a high degree of biostability. To our
knowledge, the influence of RO water on biofilm formation and growth of L.
pneumophila has not yet been investigated. Therefore, this study aimed (i)
to determine the Legionella growth potential of (remineralised) RO-water
produced by a pilot plant and to compare this to conventional treated
groundwater, and (ii) to determine if different pipe materials, in contact with
remineralised RO-water, can cause growth of L. pneumophila. The Legionella
growth potential of water was determined with the boiler biofilm monitor (BBM)
that mimics the flow of water in a premise plumbing system. The Legionella
growth potential of materials in contact with remineralised RO-water was
determined by using the biomass production potential (BPP)-test. ATP
concentrations in the biofilm on the glass rings from the BBM fed with (remineralised)
RO water fluctuated around 100 pg ATP cm-2. In contrast, BBMs fed
with conventionally treated water resulted in ten-fold higher ATP concentrations
in the biofilm. Moreover, conventionally treated water had a Legionella growth
potential that was 1000-fold higher than that of (remineralised) RO-water.
Furthermore, glass, copper and PVC-C had the lowest biofilm concentrations and Legionella
growth potential in the BPP-test, followed by PE-Xb, PE-Xc and PE-100. The
highest biofilm concentration and Legionella growth potential were with
PVC-P. Hence, our study demonstrated that remineralised RO-water did not enhance
growth of L. pneumophila in the BBM that mimics the premises plumbing
system. However, when PE or PVC-P materials are used growth of L. pneumophila
can still occur in the premises plumbing system despite the high quality of the
supplied remineralised RO-water.
E, Paranjape K, Lalancette C, Villion M, Quach C, Laferričre C, Faucher
SP, Prévost M.
Department of Civil Engineering, Polytechnique Montréal,
Montréal, QC, Canada. firstname.lastname@example.org
Water Res 2019 Jun;156:277-286.
studies have reported increased levels of Legionella
pneumophila (Lp) at points of use compared to levels in primary and
secondary components of hot water systems, suggesting possible selection by
environmental conditions. In this study, concentrations of Lp in a hospital hot
water system were evaluated by profile sampling, collecting successive water
samples to determine the prevalence at the faucet (distal) and upstream piping
before and after a system intervention to increase temperature. Lp strain
diversity was compared between different points of use and different areas of
the hot water system (i.e., tap, intermediate piping and main up flow piping).
In total, 47 isolates were recovered from 32 positive hot water samples
collected from designated taps, showers and recirculation loops; these isolates
were subsequently analyzed by sequence-based typing (SBT). Lp levels were
comparable between first draw (500 mL) and flushed (2 and 5 min) samples,
whereas a decrease was observed in the amount of culturable cells (1 log). Two
sequence types (STs) were identified throughout the system. ST378 (sg4/10) was
present in 91% of samples, while ST154-like (sg1) was present in 41%; both STs
were simultaneously recovered in 34% of samples. Isolated STs displayed
comparable tolerance to copper (0.8-5 mg/L) and temperature (55°C, 1h) exposure.
The ability to replicate within THP1 cells and Acanthamoeba castellanii
was similar between the two STs and a comparative environmental outbreak strain.
The low Lp diversity and the detection of both Lp sequence types in repeated
subsequent samples collected from positive faucets in a hospital wing suggest a
minimal impact of the distal conditions on strain selection for the sampled
points, as well as a possible adaptation to stressors present in the system,
leading to the predominance of a few strains.
Scott C, Ashbolt NJ.
School of Public Health, University of Alberta, Edmonton, Alberta,
Int J Hyg Environ Health 2019 May;222(4):678-686.
Abstract: Prolific growth of pathogenic Legionella
pneumophila within engineered water systems and premise plumbing, and human
exposure to aerosols containing this bacterium results in the leading health
burden of any water-related pathogen in developed regions. Ecologically,
free-living amoebae (FLA) are an important group of the microbial community that
influence biofilm bacterial diversity in the piped-water environment. Using
fluorescent microscopy, we studied in-situ the colonization of L. pneumophila
in the presence of two water-related FLA species, Willaertia magna and Acanthamoeba
polyphaga in drinking water biofilms. During water flow as well as after
periods of long-stagnation, the attachment and colonization of L. pneumophila
to predeveloped water-biofilm was limited. Furthermore, W. magna and A.
polyphaga showed no immediate interactions with L. pneumophila when
introduced to the same natural biofilm environment. A. polyphaga encysted
within 5-7 d after introduction to the tap-water biofilms and mostly persisted
in cysts till the end of the study period (850 d). W. magna trophozoites,
however, exhibited a time delay in feeding on Legionella and were
observed with internalized L. pneumophila cells after 3 weeks from their
introduction to the end of the study period and supported putative (yet limited)
intracellular growth. The culturable L. pneumophila in the bulk water was
reduced by 2-log over 2 years at room temperature but increased (without a
change in mip gene copies by qPCR) when the temperature was elevated to 40°C
within the same closed-loop tap-water system without the addition of nutrients
or fresh water. The overall results suggest that L. pneumophila maintains
an ecological balance with FLA within the biofilm environment, and higher
temperature improve the viability of L. pneumophila cells, and
intracellular growth of Legionella is possibly cell-concentration
dependent. Observing the preferential feeding behavior, we hypothesize that an
initial increase of FLA numbers through feeding on a range of other available
bacteria could lead to an enrichment of L. pneumophila, and later force
predation of Legionella by the amoeba trophozoites results in rapid
intracellular replication, leading to problematic concentration of L.
pneumophila in water. In order to find sustainable control options for
legionellae and various other saprozoic, amoeba-resisting bacterial pathogens,
this work emphasizes the need for better understanding of the FLA feeding
behavior and the range of ecological interactions impacting microbial population
dynamics within engineered water systems.
Donohue MJ, King D, Pfaller S, Mistry JH.
National Exposure Research Laboratory, United States
Environmental Protection Agency, Cincinnati, OH, USA. email@example.com
J Appl Microbiol 2019
Abstract: Aim: Premise
plumbing may disseminate the bacteria Legionella pneumophila and Mycobacterium
avium, the causative agents for legionellosis and pulmonary nontuberculous
mycobacterium disease respectively. Methods and
quantitative PCR, the occurrence and persistence of L. pneumophila, L.
pneumophila serogroup (Sg)1 and M. avium were evaluated in drinking
water samples from 108 cold water taps (residences: n=43) and (office buildings:
n=65). Mycobacterium avium, L. pneumophila and L. pneumophila
Sg1 were detected 45, 41 and 25% of all structures respectively. Two occurrence
patterns were evaluated: sporadic (a single detection from the three samplings)
and persistent (detections in two or more of the three samples). Conclusions: The
micro-organism's occurrence was largely sporadic. Office buildings were prone to
microbial persistence independent of building age and square footage. Microbial
persistence at residences was observed in those older than 40 years for L.
pneumophila and was rarely observed for M. avium. The microbial
occurrence was evenly distributed between structure types but there were
differences in density and persistence. Significance
of and impact of the study: The
study is important because residences are often suspected to be the source when
a case of disease is reported. These data demonstrate that this may not be the
case for a sporadic incidence.
De Giglio O, Napoli C,
Apollonio F, Brigida S, Marzella A, Diella G, Calia C, Scrascia M, Pacifico C,
Pazzani C, Uricchio VF, Montagna MT.
Department of Biomedical Science and Human Oncology, University of Bari
"Aldo Moro", Bari, Italy. firstname.lastname@example.org
Environ Res 2019
Abstract: Legionellae are opportunistic bacteria that
cause various conditions after exposure to contaminated aerosols, ranging from a
serious type of pneumonia to a mild case of an influenza-like illness. Despite
the risks of exposure, little is known about the occurrence of Legionella
in natural environments and, even though studies have shown that there is a
potential risk of transmission via inhalation, it does not have to be detected
in groundwater that is used for irrigation. The culture methods traditionally
used to detect Legionella have several limits that can be partly solved
by applying molecular techniques. Samples from 177 wells in Apulia, Southern
Italy, were collected twice, in winter and in summer, and analyzed. When
compared with the guidelines, 145 (81.9%) of the sampled wells were suitable for
irrigation use. The culture-based method highlighted the presence of different
species and serogroups of Legionella in 31 (21.2%) of the 145 wells that
were shown to be suitable for irrigation use. A greater number of wells returned
positive results for Legionella in summer than in winter (p=0.023), and
the median concentrations were mostly higher in summer (500 CFU/L) than in
winter (300 CFU/L). The median temperature in the Legionella positive
well waters was significantly higher than that in the negative ones, both in
winter and in summer (p<0.001). Using molecular techniques, Legionella non-pneumophila
was found in 37 of the 114 wells earlier detected as suitable for irrigation use
but negative for Legionella by the culture-based methods. The
distribution of Legionella differs significantly in porous aquifers
compared to the karst-fissured ones both with quantitative polymerase chain
reaction (qPCR) (p=0.0004) and viable cells by propidium monoazide (PMA-qPCR)
(p=0.0000). Legionella concentrations were weakly correlated with
temperature of water both with qPCR (ρ=0.47,
p=0.0033) and PMA-qPCR (ρ=0.41, p=0.0126). Our data suggest that water that aerosolizes when
sprinkled on plants represents a potential source of Legionellosis, with a
higher risk from exposure in summer. On a practical level, this finding is
important for workers (farmers and gardeners) who are in contact with waters
used for irrigation.
Hayes-Phillips D, Bentham R, Ross K, Whiley H.
College of Science and Engineering, Flinders University, GPO Box 2100,
Adelaide 5001, Australia. Harriet.Whiley@flinders.edu.au
Pathogens 2019 Feb;8(1):27.
Abstract: Legionnaires' disease is a potentially fatal
pneumonia like infection caused by inhalation or aspiration of water particles
contaminated with pathogenic Legionella spp. Household showers
have been identified as a potential source of sporadic, community-acquired
Legionnaires' disease. This study used qPCR to enumerate Legionella spp.
and Legionella pneumophila in water samples collected from
domestic showers across metropolitan Adelaide, South Australia. A survey was
used to identify risk factors associated with contamination and to examine
awareness of Legionella control in the home. The hot water
temperature was also measured. A total of 74.6% (50/68) and 64.2% (43/68)
showers were positive for Legionella spp. and L.
associations were found between Legionella spp. concentration
and maximum hot water temperature (p=0.000), frequency of shower use (p=0.000)
and age of house (p=0.037). Lower Legionella spp.
concentrations were associated with higher hot water temperatures, showers used
at least every week and houses less than 5 years old. However, examination of
risk factors associated with L. pneumophila found that there
were no statistically significant associations (p>0.05) with L.
pneumophila concentrations and temperature, type of hot water system,
age of system, age of house or frequency of use. This study demonstrated that
domestic showers were frequently colonized by Legionella spp.
and L. pneumophila and should be considered a potential source
of sporadic Legionnaires' disease. Increasing hot water temperature and running
showers every week to enable water sitting in pipes to be replenished by the
municipal water supply were identified as strategies to reduce the risk of Legionella in
showers. The lack of public awareness in this study identified the need for
public health campaigns to inform vulnerable populations of the steps they can
take to reduce the risk of Legionella contamination and
Caicedo C, Rosenwinkel KH,
Exner M, Verstraete W, Suchenwirth R, Hartemann P, Nogueira R.
Leibniz University Hannover, Institute for Sanitary Engineering and Waste Management, Hannover, 30167, Germany. email@example.com e firstname.lastname@example.org
Water Res 2019 Feb;149:21-34.
Abstract: Wastewater treatment plants (WWTPs) have been
identified as confirmed but until today underestimated sources of Legionella,
playing an important role in local and community cases and outbreaks of
Legionnaires' disease. In general, aerobic biological systems provide an optimum
environment for the growth of Legionella due to high organic nitrogen and
oxygen concentrations, ideal temperatures and the presence of protozoa. However,
few studies have investigated the occurrence of Legionella in WWTPs, and
many questions in regards to the interacting factors that promote the
proliferation and persistence of Legionella in these treatment systems
are still unanswered. This critical review summarizes the current knowledge
about Legionella in municipal and industrial WWTPs, the conditions that
might support their growth, as well as control strategies that have been applied.
Furthermore, an overview of current quantification methods, guidelines and
health risks associated with Legionella in reclaimed wastewater is also
discussed in depth. A better understanding of the conditions promoting the
occurrence of Legionella in WWTPs will contribute to the development of
improved wastewater treatment technologies and/or innovative mitigation
approaches to minimize future Legionella outbreaks.
D, Gautsch S, Spieler-Denz R, Dubuis O, Gaia V,
Moran-Gilad J, Hinic V, Seth-Smith HM, Nickel CH, Tschudin-Sutter S, Bassetti S,
Haenggi M, Brodmann P, Fuchs S, Egli A.
Division of Clinical Microbiology, University Hospital
Basel, Basel, Switzerland.
Euro Surveill 2019 Jan;24(4):1800192.
Abstract: Introduction: Water supply and air-conditioner
cooling towers (ACCT) are potential sources of Legionella pneumophila infection
in people. During outbreaks, traditional typing methods cannot sufficiently
segregate L. pneumophila strains to reliably trace back
transmissions to these artificial water systems. Moreover, because multiple L.
pneumophila strains may be present within these systems, methods to
adequately distinguish strains are needed. Whole genome sequencing (WGS) and
core genome multilocus sequence typing (cgMLST), with their higher resolution
are helpful in this respect. In summer 2017, the health administration of the
city of Basel detected an increase of L. pneumophila infections
compared with previous months, signalling an outbreak. Aim: We aimed to identify L.
pneumophila strains populating suspected environmental sources of the
outbreak, and to assess the relations between these strains and clinical
outbreak strains. Methods: An epidemiological and WGS-based microbiological
investigation was performed, involving isolates from the local water supply and
two ACCTs (n=60), clinical outbreak and non-outbreak related isolates from 2017
(n = 8) and historic isolates from 2003-2016 (n=26). Results: In both ACCTs,
multiple strains were found. Phylogenetic analysis of the ACCT isolates showed a
diversity of a few hundred allelic differences in cgMLST. Furthermore, two
isolates from one ACCT showed no allelic differences to three clinical isolates
from 2017. Five clinical isolates collected in the Basel area in the last decade
were also identical in cgMLST to recent isolates from the two ACCTs. Conclusion:
Current outbreak-related and historic isolates were linked to ACCTs, which form
a complex environmental habitat where strains are conserved over years.
McColm S, McElmurry SP, Kilgore PE, Sobeck J, Sadler R, Love NG, Swanson MS.
Department of Microbiology and Immunology,
University of Michigan, Ann Arbor, Michigan, USA. email@example.com
Coinciding with major changes to its municipal water system, Flint, MI, endured
Legionnaires' disease outbreaks in 2014 and 2015. By sampling premise plumbing
in Flint in the fall of 2016, we found that 12% of homes harbored legionellae, a
frequency similar to that in residences in neighboring areas. To evaluate the
genetic diversity of Legionella pneumophila in Southeast
Michigan, we determined the sequence type (ST) and serogroup (SG) of the 18
residential isolates from Flint and Detroit, MI, and the 33 clinical isolates
submitted by hospitals in three area counties in 2013 to 2016. Common to one
environmental and four clinical samples were strains of L. pneumophila SG1
and ST1, the most prevalent ST worldwide. Among the Flint premise plumbing
isolates, 14 of 16 strains were of ST367 and ST461, two closely related SG6
strain types isolated previously from patients and corresponding environmental
samples. Each of the representative SG1 clinical strains and SG6 environmental
isolates from Southeast Michigan infected and survived within macrophage
cultures at least as well as a virulent laboratory strain, as judged by
microscopy and by enumerating CFU. Likewise, 72 h after infection, the yield of
viable-cell counts increased >100-fold for each of the representative SG1
clinical isolates, Flint premise plumbing SG6 ST367 and -461 isolates, and two
Detroit residential isolates. We verified by immunostaining that SG1-specific
antibody does not cross-react with the SG6 L. pneumophila environmental
strains. Because the widely used urinary antigen diagnostic test does not
readily detect non-SG1 L. pneumophila, Legionnaires' disease caused
by SG6 L. pneumophila is likely underreported worldwide.
IMPORTANCE: L. pneumophila is the leading cause of disease outbreaks
associated with drinking water in the United States. Compared to what is known
of the established risks of colonization within hospitals and hotels, relatively
little is known about residential exposure to L. pneumophila One
year after two outbreaks of Legionnaires' disease in Genesee County, MI, that
coincided with damage to the Flint municipal water system, our multidisciplinary
team launched an environmental surveillance and laboratory research campaign
aimed at informing risk management strategies to provide safe public water
supplies. The most prevalent L. pneumophila strains isolated
from residential plumbing were closely related strains of SG6. In laboratory
tests of virulence, the SG6 environmental isolates resembled SG1 clinical
strains, yet they are not readily detected by the common diagnostic urinary
antigen test, which is specific for SG1. Therefore, our study complements the
existing epidemiological literature indicating that Legionnaires' disease due to
non-SG1 strains is underreported around the globe.
Kyritsi MA, Mouchtouri
VA, Katsioulis A, Kostara E, Nakoulas V, Hatzinikou M, Hadjichristodoulou C.
Department of Hygiene and Epidemiology, Medical School, University of
Thessaly, 41222 Larissa, Greece. firstname.lastname@example.org
Int J Environ Res Public Health 2018
Abstract: This study aimed to assess the colonization of
hotel water systems in central Greece and Corfu by Legionella, and
to investigate the association between physicochemical parameters and Legionella colonization.
Standardized hygiene inspection was conducted in 51 hotels, and 556 water
samples were analyzed for Legionella spp. Free
chlorine concentration, pH, hardness, conductivity, and trace metals were
defined in cold water samples. The results of inspections and chemical analyses
were associated with the microbiological results using univariate and logistic
regression analysis. According to the score of the checklist used for the
inspections, 17.6% of the hotels were classified as satisfactory, 15.7% as
adequate, and 66.7% as unsatisfactory. Moreover, 74.5% of the hotels were
colonized by Legionella spp. and 31.4% required remedial
measures according to the European guidelines. Legionella spp. were
isolated in 28% of the samples. Unsatisfactory results of inspections were
associated with Legionella presence (relative risk (RR)=7.67, p-value=0.043).
In hot-water systems, <50°C temperatures increased the risk of Legionella colonization
(RR=5.36, p-value<0.001). In cold-water systems, free chlorine
concentration <0.375 mg/L (odds ratio (OR)=9.76, p-value=0.001),
pH ≥7.45 (OR=4.05, p-value=0.007), and hardness≥321
mgCaCO₃/L (OR=5.63, p-value=0.003)
increased the risk, whereas copper pipes demonstrated a protective role
(OR=0.29, p-value=0.0024). The majority of the hotels inspected were
colonized with Legionella. Supplementary monitoring of the risk
factors that were identified should be considered.
Bahrami A, Nabizadeh E, Amini Y, Esmaeili D.
Microbiology Research Center, Systems Biology and Poisonings Institute,
Baqiyatallah University of Medical Sciences, Teheran, Iran. email@example.com
Iran J Med Sci 2018
Abstract: Background: Legionella species
are ubiquitous and naturally found in lakes, rivers, streams and hot springs,
and other water resources. The present study aimed to investigate the prevalence
of Legionella species in water resources of Iran by a
systematic review and meta-analysis. Methods: In
search of papers relevant to the prevalence of Legionella in
water resources of Iran, the scientific information database in both English and
Persian languages was used. The search was limited to studies between the year
2000 and end of July 2016. Each cohort and cross-sectional study that reported
the contamination of water with Legionella was included in the
present study. For data analysis, comprehensive meta-analysis software with
Cochran's Q and I2 tests were used. P values less than 0.05 were considered
statistically significant. Results: The
prevalence of Legionella species in water resources of Iran was
27.3% (95% CI:25.3-29.3). The prevalence of Legionella spp. in
hospital water, dental settings water, and other water resources were 28.8% (95%
CI: 26.4-31.2), 23.6% (95% CI:16.1-33.2), and 29.6% (95% CI:25.6-33.8),
respectively. The most common Legionella species was L.
pneumophila with a prevalence of 60.5% (95% CI:53.3-67.2) and the
prevalence of all other species was 52.5% (95% CI:44.7-60.2). The highest
prevalence was reported in Isfahan with 55.7% (95% CI:48.0-63.0).
Conclusion: Based on the results,
the prevalence rate of Legionella species in water resources of
Iran was high and the most common Legionella species was L.
David S, Mentasti M, Lai S, Vaghji L, Ready D, Chalker VJ, Parkhill
Pathogen Genomics, Wellcome Sanger Institute, Wellcome
Genome Campus, Hinxton, Cambridge, UK.
Respiratory and Vaccine Preventable Bacteria Reference
Unit, Public Health England, Colindale, London, UK. firstname.lastname@example.org
Microb Genom 2018
Abstract: The diversity of Legionella
pneumophila populations within single water systems is not well understood,
particularly in those unassociated with cases of Legionnaires' disease. Here, we
performed genomic analysis of 235 L. pneumophila isolates obtained from
28 water samples in 13 locations within a large occupational building. Despite
regular treatment, the water system of this building is thought to have been
colonized by L. pneumophila for at least 30 years without evidence of
association with Legionnaires' disease cases. All isolates belonged to one of
three sequence types (STs), ST27 (n=81), ST68 (n=122) and ST87 (n=32), all three
of which have been recovered from Legionnaires' disease patients previously.
Pairwise single nucleotide polymorphism differences amongst isolates of the same
ST were low, ranging from 0 to 19 in ST27, from 0 to 30 in ST68 and from 0 to 7
in ST87, and no homologous recombination was observed in any lineage. However,
there was evidence of horizontal transfer of a plasmid, which was found in all
ST87 isolates and only one ST68 isolate. A single ST was found in 10/13 sampled
locations, and isolates of each ST were also more similar to those from the same
location compared with those from different locations, demonstrating spatial
structuring of the population within the water system. These findings provide
the first insights into the diversity and genomic evolution of a L.
pneumophila population within a complex water system not associated with
P, Olson ND, Paulson JN, Pop M, Maddox C, Claye
E, Rosenberg Goldstein RE, Sharma M, Gibbs SG, Mongodin EF, Sapkota AR.
Institute for Applied Environmental Health, University of Maryland School of
Public Health, MD, USA. email@example.com
Sci Total Environ 2018
Water recycling continues to expand across the United States, from areas that
have access to advanced, potable-level treated reclaimed water, to those having
access only to reclaimed water treated at conventional municipal wastewater
treatment plants. This expansion makes it important to further characterize the
microbial quality of these conventionally treated water sources. Therefore, we
used 16S rRNA gene sequencing to characterize total bacterial communities
present in differentially treated wastewater and reclaimed water (n=67 samples)
from four U.S. wastewater treatment plants and one associated spray irrigation
site conducting on-site ultraviolet treatment and open-air storage. The number
of observed operational taxonomic units was significantly lower (p<0.01) in
effluent, compared to influent, after conventional treatment. Effluent community
structure was influenced more by treatment method than by influent community
structure. The abundance of Legionella spp. increased as treatment
progressed in one treatment plant that performed chlorination and in another
that seasonally chlorinated. Overall, the alpha-diversity of bacterial
communities in reclaimed water decreased (p<0.01) during wastewater treatment
and spray irrigation site ultraviolet treatment (p<0.01), but increased
(p<0.01) after open-air storage at the spray irrigation site. The abundance
of Legionella spp. was higher at the sprinkler system pumphouse at the
spray irrigation site than in the influent from the treatment plant supplying
the site. Legionella pneumophila was detected in conventionally treated
effluent samples and in samples collected after ultraviolet treatment at the
spray irrigation site, while Legionella feeleii persisted throughout
on-site treatment at the spray irrigation site, and, along with Mycobacterium
gordonae, was also detected at the sprinkler system pumphouse at the spray
irrigation site. These data could inform the development of future treatment
technologies and reuse guidelines that address a broader assemblage of the
bacterial community of reclaimed water, resulting in reuse practices that may be
more protective of public health.
L, Moore G.
Biosafety, Air and Water Microbiology
Group, National Infection Service, Public Health England, Porton Down, Salisbury
SP4 0JG, UK.
Perspect Public Health 2018
Aims: To determine
the presence and prevalence of Legionella spp in domestic rainwater
storage butts and to quantify its aerosolisation when collected
rainwater is used for common gardening activities. Methods: Volunteers
were asked to take a water sample from their garden rainwater storage butt. The
presence of Legionella was determined using quantitative polymerase chain
reaction (qPCR). Two new rainwater storage butts were installed on-site at PHE
Porton and positioned in sunlight or in the shade. Ambient conditions and those
within the two 'experimental' water butts were continually monitored. A cyclone
air sampler was used to detect the presence of Legionella in the air when
collected rainwater was poured from a watering can or delivered via a hosepipe
attached to a submersible water butt pump. Results: A
total of 63 volunteers provided water samples from 113 different rainwater
storage butts. Legionella spp was detected in 107 of these samples at a
mean concentration of 4.7×104 genomic units l-1. Two
of these samples also contained L. pneumophila. The water butt positioned
in the shade stored water at a significantly lower temperature than that exposed
to sunlight. While the concentration of Legionella was significantly
higher in this cooler water, meteorological conditions rather than conditions
within the water butt had the greatest effect upon Legionella
concentration. No Legionella was detected in the air when rainwater was
poured from a watering can. However, using a hose pipe on a 'fine spray' setting
increased both the number of organisms detected in the air and their
dissemination. Conclusion: In
this study, Legionella spp were common contaminants of collected
rainwater. However, the use of rainwater for common gardening activities should
not be discouraged. Aerosolisation of Legionella
when using a watering can is minimal and any increased risk associated with hose
pipe use can be mitigated by using a coarse spray setting.
IL, Gerba CP.
of Soil, Water and Environmental Science, University of Arizona, 2959 W. Calle
Agua Nueva, Tucson, AZ, 85745, USA. firstname.lastname@example.org
Water Res 2018 Aug;139:101-107.
Legionella pneumophila has been detected in reclaimed water used for
spray irrigation of turfgrass in public parks and golf courses. This study
determined the risks of infection from exposure to various levels of Legionella
in reclaimed waters considering: the method of spray application; and the
duration and frequency of exposure. Evaluation of these factors resulted in a
risk of infection greater than 1:10,000 for several scenarios when the number of
Legionella in the reclaimed water exceeded 1000 colony-forming units (CFU)
per ml. Most current guidelines for control of Legionella in distribution
systems recommend that increased monitoring or remedial action be taken when Legionella
levels exceed 1000 to 10,000 CFU/ml. Based upon our risk assessment, these
guidelines seem appropriate for reclaimed water systems where spray irrigation
M, Furuya N, Hosokawa N, Kanamori H,
Kaku M, Koide M, Higa F, Fujita J.
of Infection Control and Laboratory Diagnostics, Tohoku University Graduate
School of Medicine, Sendai, Japan. email@example.com
Am J Infect Control 2018
In a tertiary hospital, Legionella spp were isolated from taps and from
ward dishwashers connected to contaminated tap piping. Our investigation
revealed favorable conditions for growth of Legionella and showed that Legionella
pneumophila SG6 isolates from the taps and dishwashers were all genetically
identical by repetitive-element polymerase chain reaction. These results suggest
that contaminated dishwashers might be a potential reservoir for the spread of Legionella
in health care facilities.
De Filippis P,
Mozzetti C, Messina A, D'Alň GL.
Section of Hygiene, Department of
Biomedicine and Prevention, University of Rome "Tor Vergata", Rome,
Brief 2018 Jul;19:2364-2373.
The data presented in this article are related to the research paper titled
"Prevalence of Legionella in retirement homes and group homes water
distribution systems" (De Filippis, 2018) . Most of the cases of Legionella
infection are sporadic and occur in community-dwellers. Hot water and biofilm
samples from the showerheads of 26 retirement homes and 9 group homes hosting
closed communities were collected, in order to evaluate the prevalence of Legionella
and generic water quality parameters (Heterotrophic Plate Counts at 22°C and 37°C).
Samples were tested by culture method for the presence of Legionella.
Confirmation and identification were carried out through Latex test and PCR.
Further data about buildings' number of floors and rooms were collected and put
in relation to the presence of Legionella through constructing
contingency tables and performing exact fisher׳s
or Chi-square tests. Cold (<30°C) water samples are analyzed apart.
McLain J, Bowers J, Engelthaler DM, Edwards MA, Pruden A.
Department of Civil and Environmental
Engineering, Virginia Tech, Blacksburg, Virginia, USA. firstname.lastname@example.org
Environ Sci Technol 2018 Jul;52(16):9056-9068.
Need for global water security has spurred growing interest in wastewater reuse
to offset demand for municipal water. While reclaimed (i.e., non-potable)
microbial water quality regulations target fecal indicator bacteria,
opportunistic pathogens (OPs), which are subject to regrowth in distribution
systems and spread via aerosol inhalation and other non-ingestion routes, may be
more relevant. This study compares the occurrences of five OP gene markers (Acanthamoeba
spp., Legionella spp., Mycobacterium spp., Naegleria fowleri,
Pseudomonas aeruginosa) in reclaimed versus potable water distribution
systems and characterizes factors potentially contributing to their regrowth.
Samples were collected over four sampling events at the point of compliance for
water exiting treatment plants and at five points of use at four U.S. utilities
bearing both reclaimed and potable water distribution systems. Reclaimed water
systems harbored unique water chemistry (e.g., elevated nutrients), microbial
community composition, and OP occurrence patterns compared to potable systems
examined here and reported in the literature. Legionella spp. genes, Mycobacterium
spp. genes, and total bacteria, represented by 16S rRNA genes, were more
abundant in reclaimed than potable water distribution system samples
(p≤0.0001). This work suggests that further consideration should be given
to managing reclaimed water distribution systems with respect to non-potable
exposures to OPs.
University of Michigan-Flint School of
Nursing, Flint, MI, USA. email@example.com
Black Nurses Assoc 2018 Jul;29(1):44-50.
Abstract: The water crisis in Flint, Michigan raised national awareness about lead-
tainted drinking water, particularly its harm to children and pregnant and
lactating women. However, according to recent findings, there may be another
by-product of this man-made crisis. Failure to use anticorrosive material in the
water, a practice mandated by the 1978 Clean Water Act, is being linked to an
outbreak of Legionnaires' disease, an illness detrimental primarily to adults
over 65 years of age. While Legionnaires' disease is relatively rare, it is also
likely to remain undiagnosed. Clinicians, therefore, are urged to consider this
diagnosis in adults with pneumonia that does not respond to typical antibiotic
treatment, and in newborns with respiratory distress along with other
non-typical symptoms as well as those who have had water births or who were
exposed to ultrasonic, cool-mist humidification.
Hamilton KA, Hamilton MT,
Johnson W, Jjemba P, Bukhari Z, LeChevallier M, Haas CN.
Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104, USA. firstname.lastname@example.org
Water Res 2018 May;34:261-279.
Abstract: The use of reclaimed water brings new challenges
for the water industry in terms of maintaining water quality while increasing
sustainability. Increased attention has been devoted to opportunistic pathogens,
especially Legionella pneumophila, due to its growing importance as a
portion of the waterborne disease burden in the United States. Infection occurs
when a person inhales a mist containing Legionella bacteria. The top
three uses for reclaimed water (cooling towers, spray irrigation, and toilet
flushing) that generate aerosols were evaluated for Legionella health
risks in reclaimed water using quantitative microbial risk assessment (QMRA).
Risks are compared using data from nineteen United States reclaimed water
utilities measured with culture-based methods, quantitative PCR (qPCR), and
ethidium-monoazide-qPCR. Median toilet flushing annual infection risks exceeded
10-4 considering multiple toilet types, while median clinical
severity infection risks did not exceed this value. Sprinkler and cooling tower
risks varied depending on meteorological conditions and operational
characteristics such as drift eliminator performance. However, the greatest
differences between risk scenarios were due to 1) the dose response model used (infection
or clinical severity infection) 2) population at risk considered (residential or
occupational) and 3) differences in laboratory analytical method. Theoretical
setback distances necessary to achieve a median annual infection risk level of
10-4 are proposed for spray irrigation and cooling towers. In
both cooling tower and sprinkler cases, Legionella infection risks were
non-trivial at potentially large setback distances and indicate other
simultaneous management practices could be needed to manage risks. The
sensitivity analysis indicated that the most influential factors for variability
in risks were the concentration of Legionella and aerosol partitioning
and/or efficiency across all models, highlighting the importance of strategies
to manage Legionella occurrence in reclaimed water.
Benowitz I, Fitzhenry R, Boyd C,
Dickinson M, Levy M, Lin Y, Nazarian E, Ostrowsky B, Passaretti T, Rakeman J,
Saylors A, Shamoonian E, Smith TA, Balter S.
Division of Healthcare Quality Promotion, CDC, Atlanta, Georgia, USA. email@example.com
J Environ Health 2018 Apr;80(8):8-12.
Abstract: We investigated an outbreak of eight Legionnaires' disease cases among
persons living in an urban residential community of 60,000 people. Possible
environmental sources included two active cooling towers (air-conditioning units
for large buildings) <1 km from patient residences, a market misting system,
a community-wide water system used for heating and cooling, and potable water.
To support a timely public health response, we used real-time polymerase chain
reaction (PCR) to identify Legionella DNA in environmental
samples within hours of specimen collection. We detected L. pneumophila serogroup
1 DNA only at a power plant cooling tower, supporting the decision to order
remediation before culture results were available. An isolate from a power plant
cooling tower sample was indistinguishable from a patient isolate by
pulsed-field gel electrophoresis, suggesting the cooling tower was the outbreak
source. PCR results were available <1 day after sample collection, and
culture results were available as early as 5 days after plating. PCR is a
valuable tool for identifying Legionella DNA in environmental
samples in outbreak settings.
Papadakis A, Chochlakis D, Sandalakis V, Keramarou M, Tselentis Y, Psaroulaki
Department of Clinical Microbiology and Microbial Pathogenesis, School of
Medicine, University of Crete, Crete, Greece. firstname.lastname@example.org
Int J Environ Res Public Health 2018
Abstract: Several Travel-associated Legionnaires' disease
(TALD) cases occur annually in Europe. Except from the most obvious sites (cooling
towers and hot water systems), infections can also be associated with
recreational, water feature, and garden areas of hotels. This argument is of
great interest to better comprehend the colonization and to calculate the risk
to human health of these sites. From July 2000-November 2017, the public health
authorities of the Island of Crete (Greece) inspected 119 hotels associated with
TALD, as reported through the European Legionnaires' Disease Surveillance
Network. Five hundred and eighteen samples were collected from decorative
fountain ponds, showers near pools and spas, swimming pools, spa pools, garden
sprinklers, drip irrigation systems (reclaimed water) and soil. Of those, 67
(12.93%), originating from 43 (35.83%) hotels, tested positive for Legionella (Legionella
pneumophila serogroups 1, 2, 3, 6, 7, 8, 13, 14, 15 and non-pneumophila
species (L. anisa, L. erythra, L. taurinensis, L.
birminghamensis, L. rubrilucens). A Relative Risk (R.R.)>1 (p<0.0001)
was calculated for chlorine concentrations of less than 0.2 mg/L (R.R.: 54.78),
star classification (<4) (R.R.:4.75) and absence of Water Safety Plan
implementation (R.R.:3.96). High risk (≥10⁴ CFU/L) was estimated for
pool showers (16.42%), garden sprinklers (7.46%) and pool water (5.97%).
Scapoli L, Contaldo M, Santoro R, Palmieri A, Pezzetti F, Lauritano D, Candotto
V, Mucchi D, Baggi L, Tagliabue A, Tettamanti L.
Department of Medicine and Surgery,
University of Insubria, Varese, Italy.
J Biol Regul Homeost Agents 2018
Jan-Feb;32(2 Suppl. 1):139-142.
Abstract: Legionella spp. are
ubiquitous in aquatic habitats and water distribution systems, including dental
unit waterlines. Surveys have shown that the percentage of samples taken at
different dental sites that were positive for Legionella spp. were highly
variable and ranged from 0% to 100%. Cultivation is the principal approach to
evaluating bacterial contamination employed in the past but applying this
approach to testing for Legionella spp. may result in false-negative data
or underestimated bacterial counts. PCR and direct fluorescent counts can detect
viable non-cultivable bacteria, which are not counted by plating procedures. Legionella
spp. commonly form such viable non-culturable cells and it is likely that they
contribute to the difference between plate count results and those of PCR and
fluorescent-antibody detection. However, studies have shown that Legionella
is present in the municipal water source in spite of the current filtration and
chlorination procedures. Once Legionella reaches the building water
system, it settles down into a biofilm layer of stagnant water. By means of this
layer, Legionella can protect itself from antimicrobial agents and then
multiply. Dental unit waterlines may be contaminated with opportunistic bacteria.
The water quality in the dental units should be controlled to eliminate
opportunistic pathogens and to provide water for dental treatment that meets
public health standards for potable water.
CE, Whiley H, Edwards JW, Ross KE.
Environmental Health, Science and
Engineering, Flinders University, Adelaide, Australia. email@example.com
J Environ Public Health 2018
To address concern regarding water sustainability, the Australian Federal
Government and many state governments have implemented regulatory mechanisms and
incentives to support households to purchase and install rainwater harvesting
systems. This has led to an increase in rainwater harvesting in regional and
urban Australia. This review examines the implementation of the regulatory
mechanisms across Australia. In addition, the literature investigating the
potential health consequences of rainwater consumption in Australia was explored.
Studies demonstrated that although trace metals such as arsenic, cadmium,
chromium, lead, and iron were present in Australian rainwater, these metallic
elements were generally found below the health limit guideline, except in high
industrial areas. In addition, pathogenic or indicator microorganisms that
include, but are not limited to, Escherichia coli, total and faecal
coliforms, Campylobacter, Salmonella, Legionella, Pseudomonas, Cryptosporidium,
Enterococci, Giardia, Aeromonas, and Mycobacterium
avium Complex (MAC) have been detected in rainwater collected in
Australia. However, epidemiological evidence suggests that drinking rainwater
does not increase the risk of gastrointestinal disease. It was also identified
that there is a need for further research investigating the potential for
rainwater to be a source of infection for opportunistic pathogens.
Llewellyn AC, Lucas CE,
Roberts SE, Brown EW, Nayak BS, Raphael BH, Winchell JM.
Pneumonia Response and
Surveillance Laboratory, Respiratory Disease Branch, CDC, Atlanta, GA, USA. firstname.lastname@example.org
PLoS One 2017 Dec;12(12):e0189937.
Abstract: Cooling towers (CTs) are a leading source of
outbreaks of Legionnaires' disease (LD), a severe form of pneumonia caused by
inhalation of aerosols containing Legionella bacteria. Accordingly,
proper maintenance of CTs is vital for the prevention of LD. The aim of this
study was to determine the distribution of Legionella in a subset of
regionally diverse US CTs and characterize the associated microbial communities.
Between July and September of 2016, we obtained aliquots from water samples
collected for routine Legionella testing from 196 CTs located in eight of
the nine continental US climate regions. After screening for Legionella
by PCR, positive samples were cultured and the resulting Legionella
isolates were further characterized. Overall, 84% (164) were PCR-positive,
including samples from every region studied. Of the PCR-positive samples, Legionella
spp were isolated from 47% (78), L. pneumophila was isolated from 32%
(53), and L. pneumophila serogroup 1 (Lp1) was isolated from 24% (40).
Overall, 144 unique Legionella isolates were identified; 53% (76) of
these were Legionella pneumophila. Of the 76 L. pneumophila
isolates, 51% (39) were Lp1. Legionella were isolated from CTs in seven
of the eight US regions examined. 16S rRNA amplicon sequencing was used to
compare the bacterial communities of CT waters with and without detectable Legionella
as well as the microbiomes of waters from different climate regions.
Interestingly, the microbial communities were homogenous across climate regions.
When a subset of seven CTs sampled in April and July were compared, there was no
association with changes in corresponding CT microbiomes over time in the
samples that became culture-positive for Legionella. Legionella
species and Lp1 were detected frequently among the samples examined in this
first large-scale study of Legionella in US CTs. Our findings highlight
that, under the right conditions, there is the potential for CT-related LD
outbreaks to occur throughout the US.
Nardone M, Gaudio RM, Candotto V, Carinci F.
of Morphology, Surgery and Experimental Medicine, University of Ferrara,
Ferrara, Italy. email@example.com
Oral Implantol (Rome) 2017 Nov;10(3):283-288.
aerosol produced during the use of dental instruments can spread pathogens
potentially harmful to health. Most of the pathogens found in hydraulic system
are Gram-negative aerobic heterotrophic environmental bacterial species
exhibiting very low pathogenicity, although they may be of concern in the
treatment of vulnerable patients, such as immunocompromised, medically
compromised individuals and dental team. Dental team can be exposed to
pathogenic microorganisms including cytomegalovirus, hepatitis B virus,
hepatitis C virus, herpes simplex virus and Legionella spp. Legionella
spp. are ubiquitous in hydraulic system, in fact surveys have shown that the
percentage of samples taken at different dental chairs that were positive for Legionella
spp. and ranged from 0 to 100%. The concentration of Legionella spp. in
hydraulic system may reach 1000 organisms per ml. The primary route of Legionella
spp. transmission is inhalation or aspiration of environmentally contaminated
aerosols. All dentists are required to conduct a statutory risk assessment of
their hydraulic system, in fact to comply with their legal duties, dentists must
identify and assess the sources of risk and prepare a scheme for preventing and
controlling risks. Moreover, they must monitor the quality of their hydraulic
system at least annually to ensure that they are "legionellae free".
Prussin AJ 2nd, Schwake DO, Marr LC.
Department of Civil
and Environmental Engineering, Virginia Tech, Blacksburg, VA, 24061, USA. firstname.lastname@example.org
Build Environ 2017 Oct;123:684-695.
Abstract: Legionella is a genus of pathogenic
Gram-negative bacteria responsible for a serious disease known as legionellosis,
which is transmitted via inhalation of this pathogen in aerosol form. There are
two forms of legionellosis: Legionnaires' disease, which causes pneumonia-like
symptoms, and Pontiac fever, which causes influenza-like symptoms. Legionella can
be aerosolized from various water sources in the built environment including
showers, faucets, hot tubs/swimming pools, cooling towers, and fountains.
Incidence of the disease is higher in the summertime, possibly because of
increased use of cooling towers for air conditioning systems and differences in
water chemistry when outdoor temperatures are higher. Although there have been
decades of research related to Legionella transmission, many
knowledge gaps remain. While conventional wisdom suggests that showering is an
important source of exposure in buildings, existing measurements do not provide
strong support for this idea. There has been limited research on the potential
for Legionella transmission through heating, ventilation, and
air conditioning (HVAC) systems. Epidemiological data suggest a large proportion
of legionellosis cases go unreported, as most people who are infected do not
seek medical attention. Additionally, controlled laboratory studies examining
water-to-air transfer and source tracking are still needed. Herein, we discuss
ten questions that spotlight current knowledge about Legionella transmission
in the built environment, engineering controls that might prevent future disease
outbreaks, and future research that is needed to advance understanding of
transmission and control of legionellosis.
KA, Ahmed W, Toze S, Haas CN.
University, Philadelphia, PA, USA. email@example.com
Water Res 2017 Aug;119:288-303.
Abstract: A quantitative microbial risk
assessment (QMRA) of opportunistic pathogens Legionella pneumophila (LP)
and Mycobacterium avium complex (MAC) was undertaken for various uses of
roof-harvested rainwater (RHRW) reported in Queensland, Australia to identify
appropriate usages and guide risk management practices. Risks from inhalation of
aerosols due to showering, swimming in pools topped up with RHRW, use of a
garden hose, car washing, and toilet flushing with RHRW were considered for LP
while both ingestion (drinking, produce consumption, and accidental ingestion
from various activities) and inhalation risks were considered for MAC. The
drinking water route of exposure presented the greatest risks due to cervical
lymphadenitis and disseminated infection health endpoints for children and
immune-compromised populations, respectively. It is therefore not recommended
that these populations consume untreated rainwater. LP risks were up to 6 orders
of magnitude higher than MAC risks for the inhalation route of exposure for all
scenarios. Both inhalation and ingestion QMRA simulations support that while
drinking, showering, and garden hosing with RHRW may present the highest risks,
car washing and clothes washing could constitute appropriate uses of RHRW for
all populations, and toilet flushing and consumption of lettuce irrigation with
RHRW would be appropriate for non- immune-compromised populations.
Division of Environmental Health, Department of Epidemiology and
Biostatistics, College of Public Health, Temple University, Philadelphia, USA. firstname.lastname@example.org
Sci Total Environ 2017
Abstract: Lead (Pb) in public drinking water supplies has
garnered much attention since the outset of the Flint water crisis. Pb is a
known hazard in multiple environmental matrices, exposure from which results in
long-term deleterious health effects in humans. This discussion paper aims to
provide a succinct account of environmental Pb exposures with a focus on water
Pb levels (WLLs) in the United States. It is understood that there is a strong
correlation between WLLs and blood Pb levels (BLLs), and the associated health
effects. However, within the Flint water crisis, more than water chemistry and
Pb exposure occurred. A cascade of regulatory and bureaucratic failures
culminated in the Flint water crisis. This paper will discuss pertinent
regulations and responses including their limitations after an overview of the
public health effects from Pb exposure as well as discussion on our limitations
on monitoring and mitigating Pb in tap water. As the Flint water crisis also
included increased Legionnaires' disease, caused by Legionella pneumophila,
this paper will discuss factors influencing L. pneumophila growth. This
will highlight the systemic nature of changes to water chemistry and public
health impacts. As we critically analyze these important aspects of water
research, we offer discussions to stimulate future water quality research from a
new and systemic perspective to inform and guide public health decision-making.
De Filippis P, Mozzetti C, Amicosante M, D'Alň
GL, Messina A, Varrenti D, Giammattei R, Di Giorgio F, Corradi S, D'Auria A,
Fraietta R, Gabrieli R.
Section of Hygiene, Department of Biomedicine and Prevention, University
of Rome 'Tor Vergata', Rome, Italia. email@example.com
J Water Health 2017
Abstract: Critical environments, including water systems
in recreational settings, represent an important source of Legionella
pneumophila infection in humans. In order to assess the potential risk for
legionellosis, we analyzed Legionella contamination of water distribution
systems in 36 recreational facilities equipped with swimming pools. One hundred
and sixty water samples were analyzed from shower heads or taps located in
locker rooms or in bathrooms. By culture method and polymerase chain reaction,
41/160 samples were positive for Legionella from 12/36 recreational
centers. Hotels (57.1%) and sports centers (41.2%) were the most contaminated. L.
pneumophila serotypes 2-14 (25/41) were more frequently found than serotype
1 (10/41). Samples at temperature ≥30°C were more frequently positive
than samples at temperature <30°C (n=39 vs n=2, p<0.00001). The presence
of L. pneumophila was investigated by comparison with heterotrophic plate
count (HPC), an indicator of water quality. The presence of L. pneumophila
was associated more frequently with high and intermediate HPC load at 37°C,
therefore should be considered a potential source when HPC at 37°C is >10
CFU/mL. Maintenance, good hygiene practices, interventions on the hydraulic
system and regular controls must be implemented to minimize exposure to L.
pneumophila infection risk.
Sedlata Juraskova E, Sedlackova H, Janska J, Holy O, Lalova I,
Institute of Dentistry and Oral Sciences, Faculty of
Medicine and Dentistry, Palacky University Olomouc and University Hospital
Olomouc, Czech Republic. firstname.lastname@example.org
Bratisl Lek Listy 2017 May;118(5):310-314.
determine the current presence of Legionella spp. in the output water of
dental unit waterlines (DUWLs) and examine its mitigation by disinfection at the
Institute of Dentistry and Oral Sciences, Faculty of Medicine and Dentistry,
Palacky University Olomouc and University Hospital Olomouc. Material
and methods: The
first stage of our survey involved collecting samples of DUWL output water from
50 dental chair units (DCUs), and 2 samples of the incoming potable water. In
October 2015, a one-time disinfection (1% Stabimed) of DUWLs was conducted. This
was followed by collecting 10 control samples (survey stage 2). Results: From the total of 50 samples (survey stage 1), 18 samples (36.0 %) tested
positive for Legionella spp. Following the disinfection, nine of the ten
samples no longer showed any presence of Legionella. Conclusion: Based on culture results, the one-time disinfection (1% Stabimed) was
effective. We are unable to comment on the duration of positive effect of
disinfection on the occurrence of Legionella spp. in the outlet water. It
was a one-time survey.
Kanatani JI, Isobe J, Norimoto S, Kimata K, Mitsui C,
Amemura-Maekawa J, Kura F, Sata T, Watahiki M.
Department of Bacteriology, Toyama Institute of Health, 17-1
Nakataikoyama, Imizu-City, Toyama, Japan. email@example.com
J Infect Chemother 2017 May;23(5):265-270.
Abstract: Aims: We
investigated the prevalence of Legionella spp. isolated from shower water
in public bath facilities in Toyama Prefecture, Japan. In addition, we analyzed
the genetic diversity among Legionella pneumophila isolates from shower
water as well as the genetic relationship between isolates from shower water and
from stock strains previously analyzed from sputum specimens. Methods: The
isolates were characterized using serogrouping, 16S rRNA gene sequencing, and
sequence-based typing. Results: Legionella
spp. were isolated from 31/91 (34.1%) samples derived from 17/37 (45.9%) bath
facilities. Isolates from shower water and bath water in each public bath
facility were serologically or genetically different, indicating that we need to
isolate several L. pneumophila colonies from both bath and shower water
to identify public bath facilities as sources of legionellosis. The 61 L.
pneumophila isolates from shower water were classified into 39 sequence
types (STs) (index of discrimination = 0.974), including 19 new STs. Among the
39 STs, 12 STs match clinical isolates in the European Working Group for
Legionella Infections database. Notably, ST505 L. pneumophila SG 1, a
strain frequently isolated from patients with legionellosis and from bath water
in this area, was isolated from shower water. Conclusions: Pathogenic
L. pneumophila strains including ST505 strain were widely distributed in
shower water in public bath facilities, with genetic diversity showing several
different origins. This study highlights the need to isolate several L.
pneumophila colonies from both bath water and shower water to identify
public bath facilities as infection sources in legionellosis cases.
FF, Harte DJ.
of Public Health, University of Otago, Wellington; Environmental Health,
Regulation Health Protection and Emergency Management Division, Department of
Health and Human Services, Melbourne, Australia. firstname.lastname@example.org
N Z Med J 2017 May;130(1455):51-64.
Aim: To investigate
a possible link between liquefaction dust exposure and the noticeable increase
in legionellosis cases in response to major earthquakes in 2010 and 2011 that
resulted in widespread soil disturbance (liquefaction) in parts of Christchurch,
New Zealand. Method: We
culture tested liquefaction-affected soil for Legionella spp. in the six
months following the first earthquake in 2010. Thirty silt samples were
collected randomly from locations within Christchurch's metropolitan area that
were affected by liquefaction. The samples were tested to determine the presence
of Legionella using qualitative and quantitative methods.
Liquefaction-affected soil samples from three sites were further subjected to
particle size distribution analysis and determination of major oxides. A
controlled field study was established using six silt samples and one control
(commercial compost), seeded with a wild-type strain of Legionella bozemanae
serogroup (sg) 1 and persistence monitored over a 60-day period by culturing for
the presence of Legionella. Dry matter determinations were undertaken so
that total Legionella could be calculated on a dry weight basis. Results: Legionella
bacteria were undetectable after day one in the silt samples. However, L.
bozemanae sg1 was detected in the control sample for the entire study period.
study showed that the liquefaction-affected soil could not contribute directly
to the observed increase in legionellosis cases after the earthquakes due to its
inability to support growth and survival of the Legionella bacteria.
Collins S, Stevenson D, Bennett A, Walker J.
Biosafety, Air and Water Microbiology Group, National Infection Service,
Public Health England, Porton Down, Salisbury, UK. Samuel.email@example.com
Int J Hyg Environ Health 2017 Apr;220(2 Pt B):401-406.
Abstract: Household water systems have been proposed as a
source of sporadic, community acquired Legionnaires' disease. Showers represent
a frequently used aerosol generating device in the domestic setting, yet little
is known about the occurrence of Legionella spp. in these systems. This
study has investigated the prevalence of Legionella spp. by culture and
qPCR in UK household showers. Ninety-nine showers from 82 separate properties in
the South of England were sampled. Clinically relevant Legionella spp.
were isolated by culture in 8% of shower water samples representing 6% of
households. Legionella pneumophila sg1 ST59 was isolated from two showers
in one property and air sampling demonstrated its presence in the aerosol state.
A further 31% of showers were positive by Legionella spp. qPCR. By
multi-variable binomial regression modelling Legionella spp. qPCR
positivity was associated with the age of the property (p=0.02), the age of the
shower (p=0.01) and the frequency of use (p=0.09). The concentration of Legionella
spp. detected by qPCR was shown to decrease with increased frequency of use
(p=0.04) and more frequent showerhead cleaning (p=0.05). There was no
association between Legionella spp. qPCR positivity and the cold water
supply or the showerhead material (p=0.65 and p=0.71, respectively). Household
showers may be important reservoirs of clinically significant Legionella
and should be considered in source investigations. Simple public health advice
may help to mitigate the risk of Legionella exposure in the domestic
J, Buse H, Struewing I, Zhao A, Lytle D, Ashbolt N.
EPA, Office of Research and Development, Cincinnati, OH, USA. firstname.lastname@example.org
Environ Sci Pollut Res Int 2017
Opportunistic pathogens (OPs) in drinking water, like Legionella spp.,
mycobacteria, Pseudomonas aeruginosa, and free-living amobae (FLA) are a
risk to human health, due to their post-treatment growth in water systems. To
assess and manage these risks, it is necessary to understand their variations
and environmental conditions for the water routinely used. We sampled premise
tap (N cold=26, N hot=26) and shower (N shower=26)
waters in a bathroom and compared water temperatures to levels of OPs via qPCR
and identified Legionella spp. by 16S ribosomal RNA (rRNA) gene
sequencing. The overall occurrence and cell equivalent quantities (CE L-1)
of Mycobacterium spp. were highest (100%, 1.4×105), followed
by Vermamoeba vermiformis (91%, 493), Legionella spp. (59%,
146), P. aeruginosa (14%, 10), and Acanthamoeba spp. (5%, 6).
There were significant variations of OP's occurrence and quantities, and water
temperatures were associated with their variations, especially for
Mycobacterium spp., Legionella spp., and V. vermiformis. The peaks observed
for Legionella, mainly consisted of Legionella pneumophila sg1 or Legionella
anisa, occurred in the temperature ranged from 19 to 49°C, while Mycobacterium
spp. and V. vermiformis not only co-occurred with Legionella spp.
but also trended to increase with increasing temperatures. There were higher
densities of Mycobacterium in first than second draw water samples,
indicating their release from faucet/showerhead biofilm. Legionella spp.
were mostly at detectable levels and mainly consisted of L. pneumophila, L.
anisa, Legionella donaldsonii, Legionella tunisiensis, and an
unknown drinking water isolate based on sequence analysis. Results from this
study suggested potential health risks caused by opportunistic pathogens when
exposed to warm shower water with low chlorine residue and the use of Mycobacterium
spp. as an indicator of premise pipe biofilm and the control management of those
SM, Brenner B, Wunderlich A, Tuschak C, Huber S, Kolb S, Niessner R, Seidel
M, Höller C, Herr CEW.
Bavarian Health and Food Safety Authority,
Occupational and Environmental Health, Epidemiology, Munich, Germany. email@example.com
Total Environ 2017 Jan;575:1197-1202.
The urbanization of agricultural areas results in a reduction of distances
between residential buildings and livestock farms. In the public debate,
livestock farming is increasingly criticized due to environmental disturbance
and odor nuisance originating from such facilities. One method to reduce odor
and ammonia is by exhaust air treatment, for example, by biological exhaust air
purification processes with bio-trickling filters filled with tap water. Higher
temperatures in the summertime and the generation of biofilms are ideal growth
conditions for Legionella. However, there are no studies on the presence of Legionella
in the water of bio-trickling filters and the release of Legionella-containing
aerosols. Therefore, the aim of this study was to investigate Legionella
in wash water and emitted bioaerosols of a bio-trickling filter system of a
breeding sow facility. For this purpose, measurements were carried out using a
cyclone sampler. In addition, samples of wash water were taken. Legionella
were not found by culture methods. However, using molecular biological methods, Legionella
spp. could be detected in wash water as well as in bioaerosol samples. With
antibody-based methods, Legionella pneumophila were identified. Further
studies are needed to investigate the environmental health relevance of Legionella-containing
aerosols emitted by such exhaust air purification systems.