We will present data outlining the case that modern, rapid, microbiological technologies are currently available, and in many cases a better choice for assessing Legionella risk in building water systems.

1. Outline the often overlooked and underpresented limitations of the cultural method (i.e., ISO 11731)
• Incredibly long time to result (7-14+ days)
• The cultural method dramatically undercounts true Legionella population levels in building water systmes
• Reliance on cells being not only viable, but culturable. Data from our study is consistent with literature which shows that a significant portion of the viable (therefore should be of concern) Legionella populations in building water systems is not culturable. 
• High counts of "non-Legionella" species makes accurate counting of Legionella difficult 
• The cultural method is highly subjective as written. Data we have compiled from proficiency testing programs such as the CDC ELITE program demonstrate extreme variability between laboratories even with highly controlled samples.
• Correct the misconception that evaluation for Legionella via culture is always, explicitly required.
• The limitations of the cultural method put the Water Treatment Professional in a very reactive position.
2. Present data which demonstrate that qPCR is much more reliable in detecting and quantifying Legionella in varying sample types from building water systems.
• These data are from Phase 2 of our study. We presented results from Phase 1 at AWT 2021, and outlined our plans for Phases 2 and 3. We will be updating the AWT community on Phase 2 progress, and plans for Phase 3.
• At time of this publication, Phase 2 data demonstrate an incredibly high false negative rate with culture whereby samples were positive for live (viable) Legionella species via qPCR, but were unable to be cultured. 
• These data emphasize the important role modern, qPCR technologies can play in a comprehensive Water Management Plan.
3. Provide Water Treatment Professionals with strategies for when and how to employ qPCR in their Legionella monitoring strategies.
• In new Water Mangement Programs.
• qPCR is currently being used by many Water Treatment Professionals as an invaluable tool to rapidly get actionable data during investigations.
• Utilizing qPCR to detect and quanitfy Legionella puts the Water Treatment Professional in a proactive position.

Michael Loewenstein

The cultural method (i.e., ISO 11731) is often purported to be the “Gold Standard” in Legionella testing. However, there are many known problems associated with this method – the most often noted being its extraordinarily long time to result which can be up to two weeks or more. This lengthy time to result puts the water system operator in a constantly reactive position, forcing the system to be used “at risk”, or even taken out of service for weeks or months at a time, whenever a significant Legionella recovery is observed.

We reported to AWT at the 2021 Annual Convention on results from Phase I of a study we conducted evaluating three distinct modern, PCR/qPCR-based technologies that employ “live/dead” differentiation chemistries. Phase I of this study compared these methods to one another as well as to the cultural method for lab-inoculated water samples. All three rapid methods showed equivalent or better qualitative detection efficiency in one day, compared to the 7-14 days required for the cultural method. We are currently in Phase II of the study which is comparing the most promising of the three rapid methods to the cultural method, utilizing samples gathered in various end-use field applications. Thus far, we are observing an alarming trend of detection of Legionella spp. via qPCR in the same samples for which detection was missed by culture – yielding (at time of publication) a hugely disturbing 63% false negative rate with the cultural method. This is consistent with data we collected in Phase I which showed that the cultural method had poor qualitative detection efficiency at low levels of Legionella contamination.

The good news is that these data demonstrate that there are now multiple, accurate, rapid Legionella testing alternatives to the cultural method, and technical improvements in recent years make them an excellent choice for routine Legionella monitoring. From a practical perspective, it is easy to grasp how a faster time to result would mean that water treaters could be more agile in their approach to managing the health of their water systems. However these new data suggest that rapid methods, in many cases, are the optimal choice for obtaining the most accurate assessment of Legionella risk in a facility’s water system.

The sensitivity, accuracy, and faster time to result of qPCR puts the water management team in a far more proactive position to efficiently detect Legionella, assess the situation, and take appropriate steps to mitigate the risk.

Michael Loewenstein

Michael Loewenstein is the current Vice President of Scientific Consulting at Q Labs LLC in Cincinnati, OH. In this role, Mr. Loewenstein serves as the technical lead of much of Q Labs’ business including Water Treatment, and leads the Q Labs Technology Advancement Group. Mr. Loewenstein earned his B.S. in Microbiology, with a research focus in Molecular Genetics and Cellular Physiology from The Ohio State University. After graduation, Michael obtained a position in Corporate R&D Microbiology at Procter & Gamble where he focused on the development and validation of rapid/alternative microbial test methods, developed and launched preservative systems across a broad range of P&G products, and has developed particular expertise and passion for microbiological control of manufacturing. He has published several articles on this subject, including clean design, and monitoring programs of industrial and purified water systems. Michael currently serves in a volunteer capacity for several professional associations, including the AOAC Microbial Contaminants Expert Review Panel, and is a founding member of Manufacturing Hygiene Task Force of the Microbiology Committee for the Personal Care Products Council (PCPC). Michael is also looking forward to becoming more involved with the Cooling Water subcommittee of AWT!