Quantitative microbial risk assessment of Legionella pneumophila in a drinking water supply system in Israel

Sharaby, Yehonatan; Rodríguez-Martínez, Sarah; Höfle, Manfred G.; Brettar, Ingrid; Halpern, Malka

doi:10.1016/j.scitotenv.2019.03.287

Cited by 26 publications

(25 citation statements)

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“…from distributed water systems, and we are aware of only one other comparable study in the peer-reviewed literature. 47 Assuming a conversion factor of 0.97 disability-adjusted life years (DALYs) per subclinical infection 32 and 365 daily exposures per year, the Sharaby et al 47 risk estimates correspond to probabilities of subclinical infection equal to approximately 2 x 10 -6 and 7 x 10 -6 per person per daily exposure for faucet use and showering, respectively. These risk estimates are consistent with the low end of the range for pre-flush samples reported in the current study, when 0.1 % of Legionella spp.…”

Section: Resultsmentioning

confidence: 99%

Flushing of stagnant premise water systems after the COVID-19 shutdown can reduce infection risk by Legionella and Mycobacterium spp

Hozalski

LaPara

Zhao

et al. 2020

Preprint

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The unprecedented widespread closing of buildings due to the COVID-19 pandemic has allowed water to stagnate in premise plumbing systems, creating conditions that may facilitate the growth of opportunistic pathogens. In this study, we flushed and collected samples from showers in buildings that had been unoccupied for approximately two months and quantified Legionella pneumophila using a commercial cultivation-based assay. In addition, all bacteria, Legionella spp., L. pneumophila, L. pneumophila serogroup 1, non-tuberculous mycobacteria (NTM), and Mycobacterium avium complex (MAC) were analyzed using quantitative PCR (qPCR). Despite low or negligible total chlorine in the stagnant pre-flush water samples, L. pneumophila were not detected by either method; Legionella spp., NTM, and MAC, however, were widespread. Using quantitative microbial risk assessment (QMRA), estimated risks of clinical illness from exposure to legionella and MAC via showering were generally low, but the risk of subclinical infection via Legionella spp. could exceed a 10-7 daily risk threshold if just a small fraction (≥0.1 %) of those legionellae detected by qPCR are highly infectious. Flushing cold and hot water lines rapidly restored a total chlorine (as chloramine) residual and decreased all bacterial gene targets to building inlet water levels within 30 min. Following flushing, the chlorine residual rapidly dissipated and bacterial gene targets rebounded, approaching pre-flush concentrations after 6 to 7 days of stagnation. These results suggest that stagnant water in premise plumbing may contain elevated levels of opportunistic pathogens; flushing, however, can rapidly improve water quality and reduce the health risk but the improvement will be short-lived if building disuse persists.

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Section: Resultsmentioning

confidence: 99%

Flushing of stagnant premise water systems after the COVID-19 shutdown can reduce infection risk by Legionella and Mycobacterium spp

Hozalski

LaPara

Zhao

et al. 2020

Preprint

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“…Since the most health relevant ST1 (VACC1) and ST461 (VACC11) strains could be further distinguished into several MLVA-genotypes, MLVA-genotyping could provide an excellent basis for future source tracking in the West Bank. MLVA-genotyping provides an adequate resolution, and thus, a good basis for detailed studies of the health-and water-management-relevant traits of L. pneumophila [42,81,83,86] in support of a better clinical and DWDS management in the West Bank.…”

Section: Discussionmentioning

confidence: 99%

“…Another relevant point for public health and infection is the concentration of L. pneumophila in drinking water. For a site with comparable climate, Sharaby et al [86] showed the risk at high concentrations of culturable L. pneumophila in drinking water of the Oranim campus (Haifa). From this perspective, it can be regarded as good news that the level of culturable L. pneumophila in the West Bank hospitals was, on average, rather low or undetectable.…”

Section: Conceivable Health Relevance Of the L Pneumophila Mlva-8(12mentioning

confidence: 99%

Characterization of Legionella pneumophila Populations by Multilocus Variable Number of Tandem Repeats (MLVA) Genotyping from Drinking Water and Biofilm in Hospitals from Different Regions of the West Bank

et al. 2020

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The West Bank can be considered a high-risk area for Legionnaires’ disease (LD) due to its hot climate, intermittent water supply and roof storage of drinking water. Legionella, mostly L. pneumophila, are responsible for LD, a severe, community-acquired and nosocomial pneumonia. To date, no extensive assessment of Legionella spp and L. pneumophila using cultivation in combination with molecular approaches in the West Bank has been published. Two years of environmental surveillance of Legionella in water and biofilms in the drinking water distribution systems (DWDS) of eight hospitals was carried out; 180 L. pneumophila strains were isolated, mostly from biofilms in DWDS. Most of the isolates were identified as serogroup (Sg) 1 (60%) and 6 (30%), while a minor fraction comprised Sg 8 and 10. Multilocus Variable number of tandem repeats Analysis using 13 loci (MLVA-8(12)) was applied as a high-resolution genotyping method and compared to the standard Sequence Based Typing (SBT). The isolates were genotyped in 27 MLVA-8(12) genotypes (Gt), comprising four MLVA clonal complexes (VACC 1; 2; 5; 11). The major fraction of isolates constituted Sequence Type (ST)1 and ST461. Most of the MLVA-genotypes were highly diverse and often unique. The MLVA-genotype composition showed substantial regional variability. In general, the applied MLVA-method made it possible to reproducibly genotype the isolates, and was consistent with SBT but showed a higher resolution. The advantage of the higher resolution was most evident for the subdivision of the large strain sets of ST1 and ST461; these STs were shown to be highly pneumonia-relevant in a former study. This shows that the resolution by MLVA is advantageous for back-tracking risk sites and for the avoidance of outbreaks of L. pneumophila. Overall, our results provide important insights into the detailed population structure of L. pneumophila, allowing for better risk assessment for DWDS.

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“…The acceptable risk of infection set by the WHO for waterborne pathogens is less than one infection per 10000 persons per year and stipulates that risk assessment be undertaken for waterborne pathogens to demonstrate microbiologically safe water (World Health Organization, 2016). The calculation and the expression of the result of the risk differ according to the authors (Azuma et al, 2013;Bouwknegt et al, 2013;Kerry A. Hamilton et al, 2018;Schoen and Ashbolt, 2011;Sharaby et al, 2019). Indeed, the annual risk estimation varies significantly between the scenario analyses: the dose response model chosen (clinical severity, incidence of LD or/and Pontiac fever, during or after an outbreak, etc.…”

Section: Discussionmentioning

confidence: 99%

A valuable experimental setup to model exposure to Legionella’s aerosols generated by shower-like systems

et al. 2020

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The mechanism underlying Legionella aerosolization and entry into the respiratory tract remains poorly documented. In previous studies, we characterized the aerodynamic behaviour of Legionella aerosols and assessed their regional deposition within the respiratory tract using a human-like anatomical model. The aim of this study was to assess whether this experimental setup could mimic the exposure to bioaerosols generated by showers. To achieve this objective we performed experiments to measure the mass median aerodynamic diameter (MMAD) as well as the emitted dose and the physiological state of the airborne bacteria generated by a shower and two nebulizers (vibrating-mesh and jet nebulizers). The MMADs of the dispersed bioaerosols were characterized using a 12-stage cascade low-pressure impactor. The amount of dispersed airborne bacteria from a shower was quantified using a Coriolis® Delta air sampler and compared to the airborne bacteria reaching the thoracic region in the experimental setup. The physiological state and concentration of airborne Legionella were assessed by qPCR for total cells, culture for viable and cultivable Legionella (VC), and flow cytometry for viable but noncultivable Legionella (VBNC). In summary, the experimental setup developed appears to mimic the bioaerosol emission of a shower in terms of aerodynamic size distribution. Compared to the specific case of a shower used as a reference in this study, the experimental setup developed underestimates by 2 times (when the jet nebulizer is used) or overestimates by 43 times (when the vibrating-mesh nebulizer is used) the total emitted dose of airborne bacteria. To our knowledge, this report is the first showing that an experimental model mimics so closely an exposure to Legionella aerosols produced by showers to assess human lung deposition and infection in well-controlled and safe conditions.

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Quantitative microbial risk assessment of Legionella pneumophila in a drinking water supply system in Israel

Cited by 26 publications

References 50 publications

Flushing of stagnant premise water systems after the COVID-19 shutdown can reduce infection risk by Legionella and Mycobacterium spp

Flushing of stagnant premise water systems after the COVID-19 shutdown can reduce infection risk by Legionella and Mycobacterium spp

Characterization of Legionella pneumophila Populations by Multilocus Variable Number of Tandem Repeats (MLVA) Genotyping from Drinking Water and Biofilm in Hospitals from Different Regions of the West Bank

A valuable experimental setup to model exposure to Legionella’s aerosols generated by shower-like systems

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