To inform stakeholders of a novel, portable qPCR methodology and describe the validation process used to assess the effectiveness of the method for monitoring Legionella in accordance with ISO 12869. 

• Review the advantages and limitations of qPCR with respect to Legionella monitoring and explain how validation data is essential for the assessment of any Legionella qPCR detection method prior to deployment. 
• Review and describe ISO method 12869 and highlight the performance criteria that were used to validate the qPCR method, including linear regression calibration, LOD, LOQ, inclusivity/exclusivity, and reproducibility. 
• Present the results showing successful validation of the method after thoroughly meeting or exceeding the ISO 12869 performance criteria.

Suggested Author list: Jeremy Duguay, Michael Waud, Jordan Schmidt, Neil Sharma

The ability to detect Legionella rapidly and reliably is critically important to effectively manage risk in water distribution systems and cooling water circuits. The requirement for quick results is often hindered by the need to send collected samples to off-site laboratory facilities where results can take several days or even weeks. Although the gold standard and widely accepted regulatory method of detecting Legionella species remains culture-based, qPCR is an established detection and screening method that can be designed to target DNA unique to Legionella to quantitatively measure the bacterial population present within a water system in hours, rather than the typically required days. qPCR methods are now being routinely used to monitor for Legionella in water sources, but the available Legionella methods are not all the same. When dealing with organisms dangerous to public health, the consequences of false positive or negative results can be extremely serious, which necessitates robust and continual assessment and validation of any detection method, and the availability of validation data to an informed user-group able to adequately assess methodology is extremely important. 

In this study we present the validation of a quantitative polymerase chain reaction (qPCR) method for the detection of bacteria belonging to the genus Legionella species or Legionella pneumophila (serogroups 1-15) in accordance with International Standards Organization (ISO) Technical Specification 12869:2019. The results of this study are presented with special emphasis on end-user assessment of qPCR assays designed for the detection of Legionella and methods of validation applicable to any qPCR-based detection method. These methods include the determination and verification of a linear regression curve used to convert raw qPCR results into a concentration of genome units (GU) of Legionella, inclusivity and exclusivity of the designed qPCR primers, limit of detection (LOD) and limit of quantification (LOQ). In addition, real-world applications of the technology will be presented, including a third-party validation of the method on blind samples used for CDC-ELITE proficiency testing as well as an assessment of the technology in response to typical cooling water biocides.

Jeremy Duguay MSc.: Jeremy is a molecular biologist with over 15 years of biotechnology experience in the public, private and academic sectors. Currently he is an Applications Scientist with LuminUltra, where he helps clients successfully implement microbial monitoring technology to improve processes and reduce risk. With a wide-ranging background in technical sales, customer support and research and development, he takes pride in understanding customer needs and helping customers solve complex problems.