Temperature diagnostic to identify high risk areas and optimize Legionella pneumophila surveillance in hot water distribution systems

Abstract

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.

Post-Outbreak Investigation of Pseudomonas aeruginosa Faucet Contamination by Quantitative Polymerase Chain Reaction and Environmental Factors Affecting Positivity

“…27 DNA was extracted after filtration of 450 mL on a 0.45-μm mixed-cellulose esther filter using a bead-beating method followed by ammonium acetate precipitation and ethanol washes, as before. 28 Each faucet and its environment were characterized in detail, including the type of activating device, the connecting pipe material, the faucet internal diameter, the faucet alignment to the drain, and the drainage efficiency. The copper water distribution line was fed by municipal surface water with an average residual chlorine level of 0.4 mg Cl 2 /L.…”

Influence of Sampling Season and Sampling Protocol on Detection of Legionella Pneumophila Contamination in Hot Water / Paraugu Ņemšanas Sezonalitātes Un Paraugu Ņemšanas Metodes Ietekme Uz Legionella Pneumophila Kontaminācijas Noteikšanu Karstajš Ūdenī

“…The sampling method should be chosen depending on the purpose of sampling, such as post-outbreak investigation or preventive measurement. Sampling may be performed immediately after tap switching, or after at least one minute of water pre-flush, which is more representative for the characterisation of water quality in the system (Quaranta, 2012;Bedard, 2015).…”

“…Temperature control on the regular basis and implementation of water safety plan (Anonymous, 2007) is widely recognised as the first mitigation measure for L. pneumophila control in hot water distribution systems (Bedard, 2015). Effective strategies for preventing legionellosis need to involve establishment of risk-based reference values for Legionella in the water.…”

Copper-silver ionization at a US hospital: Interaction of treated drinking water with plumbing materials, aesthetics and other considerations

“…Cold water temperature in building B was similar and mostly below 25 C, which is not considered optimal for Legionella growth but may sustain the pathogen (Bedard et al, 2015).…”