Validation of quantitative real-time polymerase chain reaction for detection of Legionella pneumophila in hospital water networks

Background: Rapid monitoring of Legionella pneumophila (Lp) is essential to reduce the risk of Legionnaires' disease in healthcare facilities. However, culture results take at least eight days, delaying the implementation of corrective measures. Here, we assessed the performance of a qPCR method and determined qPCR action thresholds for the detection of Lp in hospital hot water networks (HWNs).Methods: Hot water samples (N = 459) were collected from a hospital HWN. Lp were quantified using iQ-Check & REG; Quanti real-time PCR Quantification kits (Bio-Rad) and the results were compared with those of culture. qPCR thresholds corresponding to the culture action thresholds of 10 and 1000 cfu/L were determined on a training dataset and vali-dated on an independent dataset.Results: Lp concentrations measured by culture and qPCR were correlated for both the training dataset (Spearman's correlation coefficient r = 0.687, P<0.0001) and the vali-dation dataset (r = 0.661, P<0.0001). Lp qPCR positivity thresholds corresponding to culture action thresholds of 10 cfu/L was 91 genome units (gu) per litre (sensitivity, 86.4%; negative predictive value -NPV, 93.3%) and that corresponding to culture action thresholds of 1000 cfu/L was 1048 gu/L (sensitivity, 100%; NPV, 100%).Conclusion: Detection of Lp by qPCR could be implemented with confidence in hospitals as a complement to culture in the monitoring strategy to speed up the implementation of corrective measures.& COPY; 2023 Published by Elsevier Ltd on behalf of The Healthcare Infection Society.

Automated summary

This study evaluated the performance of a qPCR method for the rapid monitoring of Legionella pneumophila (Lp) in hospital hot water networks (HWNs). The results showed that qPCR could be implemented as a complement to culture in the monitoring strategy to speed up the implementation of corrective measures.