Performance evaluation of a low throughput qPCR-based Legionella assay for utility as an onsite industrial water system monitoring method.

Legionella is a genus of bacteria found in natural aquatic environments, as well as domestic potable and industrial non-potable water systems. Legionella presents potential human health risks when aerosolized and inhaled by at-risk individuals. Populations of these organisms are commonly monitored at locations with a likelihood of proliferation and human exposure. Of specific interest to this study were industrial cooling water systems which have been implicated in outbreaks, and where it is necessary to monitor for the presence of Legionella for risk management. Legionella monitoring in industrial water systems is widely performed using culture-based testing, which faces limitations in terms of turnaround time and interferences. Molecular biology methodologies, including qPCR, are being explored as supplements to or replacements of the culture-based standard method because of faster turnaround times and lower detection limits, allowing for more rapid water remediation measures which can limit opportunities for human exposure and company liability. In this study, three methods were compared: culture-based testing by a certified and accredited lab, a lab-based, high throughput qPCR test (HT qPCR), and a low throughput qPCR test (LT qPCR) capable of being used in the field. More positive results were observed from the qPCR test methods than the culture testing, indicating improved sensitivity and specificity. The LT qPCR test allows for portable testing with quick turnaround times, which can be leveraged for environmental surveillance, process optimization, and monitoring and onsite case investigations. The LT field-deployable qPCR test had high negative predictive value and would be a useful tool for negative screening of Legionella samples from high-risk environments and/or outbreak investigations to streamline samples for culture testing.