Evaluation of a real-time PCR hybridization assay for rapid detection of Legionella pneumophila in hospital and environmental water samples.

A real-time LightCycler assay for Legionella pneumophila was evaluated with 120 water samples potentially contaminated with PCR inhibitors. Results were obtained within five hours, with a detection limit equivalent to 800 cells/L. However, 11 of 22 culture-positive samples containing < 100 CFU/L were also positive by LightCycler assay, indicating the presence of significant numbers of non-viable cells. Following extraction, amplification inhibitors remained in four culture-positive samples, but only one contained > 800 CFU/L. The assay seemed suitable for rapidly screening large sample numbers for heavy contamination with L. pneumophila, but conventional culture should continue to be used to detect low contamination levels.