Legionella pneumophila is frequently detected in hot water distribution systems and thermal control is a common measure implemented by health care facilities. A risk assessment based on water temperature profiling and temperature distribution within the network is proposed, to guide effective monitoring strategies and allow the identification of high risk areas. Temperature and heat loss at control points (water heater, recirculation, representative points-of-use) were monitored in various sections of five health care facilities hot water distribution systems and results used to develop a temperature-based risk assessment tool. Detailed investigations show that defective return valves in faucets can cause widespread temperature losses because of hot and cold water mixing. Systems in which water temperature coming out of the water heaters was kept consistently above 60 °C and maintained above 55 °C across the network were negative for Legionella by culture or qPCR. For systems not meeting these temperature criteria, risk areas for L. pneumophila were identified using temperature profiling and system's characterization; higher risk was confirmed by more frequent microbiological detection by culture and qPCR. Results confirmed that maintaining sufficiently high temperatures within hot water distribution systems suppressed L. pneumophila culturability. However, the risk remains as shown by the persistence of L. pneumophila by qPCR.

This study investigated how quickly cells of the opportunistic pathogen Pseudomonas aeruginosa recover culturability after exposure to two of the most common environmental stressors present in drinking water, free chlorine and copper ions. Viable but nonculturable (VBNC) P. aeruginosa undetected by direct culturing following exposure to free chlorine or copper ions can survive in drinking water systems, with potential to recover, multiply, and regain infectivity. Cells were exposed to copper sulfate (0.25 mg Cu(2+)  L(-1) ) or free chlorine (initial dose of 2 mg Cl2  L(-1) ) for 24 h. Despite total loss of culturability and a reduction in viability from 1.2 × 10(7) to 4 × 10(3)  cells mL(-1) (3.5 log), cells exposed to chlorine recovered viability quickly after the depletion of free chlorine, while culturability was recovered within 24 h. Copper ions did not depress viability, but reduced culturability from 3 × 10(7) to 2.3 × 10(2)  cells mL(-1) (5.1 log); VBNC cells regained culturability immediately after copper ion chelation. A comparison between direct culturing and Pseudalert, a specific enzyme-based assay, was performed. Both detection methods were well correlated in the range of 10(2) -10(10)  cells L(-1) . However, correlations between the methods declined after exposure to copper ions.

The types of faucets and connecting pipes, flow rate, and water quality are important parameters influencing the prevalence and the concentrations of P. aeruginosa in faucets. High concentrations of P. aeruginosa in the first 250 mL suggest increased risk of exposure when using the first flush.

OBJECTIVETo perform a post-outbreak prospective study of the Pseudomonas aeruginosa contamination at the faucets (water, aerator and drain) by culture and quantitative polymerase chain reaction (qPCR) and to assess environmental factors influencing occurrenceSETTINGA 450-bed pediatric university hospital in Montreal, CanadaMETHODSWater, aerator swab, and drain swab samples were collected from faucets and analyzed by culture and qPCR for the post-outbreak investigation. Water microbial and physicochemical parameters were measured, and a detailed characterization of the sink environmental and design parameters was performed.RESULTSThe outbreak genotyping investigation identified drains and aerators as the source of infection. The implementation of corrective measures was effective, but post-outbreak sampling using qPCR revealed 50% positivity for P. aeruginosa remaining in the water compared with 7% by culture. P. aeruginosa was recovered in the water, the aerator, and the drain in 21% of sinks. Drain alignment vs the faucet and water microbial quality were significant factors associated with water positivity, whereas P. aeruginosa load in the water was an average of 2 log higher for faucets with a positive aerator.CONCLUSIONSP. aeruginosa contamination in various components of sink environments was still detected several years after the resolution of an outbreak in a pediatric university hospital. Although contamination is often not detectable in water samples by culture, P. aeruginosa is present and can recover its culturability under favorable conditions. The importance of having clear maintenance protocols for water systems, including the drainage components, is highlighted.Infect. Control Hosp. Epidemiol. 2015;36(11):1283–1291

is an environmental bacterium that is commonly associated with outbreaks in neonatal intensive care units (NICUs). Investigations of outbreaks require efficient recovery and typing of clinical and environmental isolates. In this study, we investigated how the use of next-generation sequencing applications, such as bacterial whole-genome sequencing (WGS) and bacterial community profiling, could improve outbreak investigations. Phylogenomic links and potential antibiotic resistance genes and plasmids in isolates were investigated using WGS, while bacterial communities and relative abundances of in environmental samples were assessed using sequencing of bacterial phylogenetic marker genes (16S rRNA and genes). Typing results obtained using WGS for the 10 isolates recovered during a NICU outbreak investigation were highly consistent with those obtained using pulsed-field gel electrophoresis (PFGE), the current standard typing method for this bacterium. WGS also allowed the identification of genes associated with antibiotic resistance in all isolates, while no plasmids were detected. Sequencing of the 16S rRNA and genes both showed greater relative abundances of at environmental sampling sites that were in close contact with infected babies. Much lower relative abundances of were observed following disinfection of a room, indicating that the protocol used was efficient. Variations in the bacterial community composition and structure following room disinfection and among sampling sites were also identified through 16S rRNA gene sequencing. Together, results from this study highlight the potential for next-generation sequencing tools to improve and to facilitate outbreak investigations.