Rapid detection of Legionella spp in water samples by ScanVIT method: comparison of acid vs heat treatment

Background. A rapid detection of Legionella bacteria in water samples is crucial to minimize the risk of acquiring infections, especially in health care facilities. Different detection methods and different decontamination procedures have been reported to affect the recovery of Legionella spp. Our goal was to test the recovery of Legionella pneumophila and Legionella non-pneumophila species using a kit based on nonspecific and species-specific probes to treat water samples after two different decontamination procedures. Methods. The study was conducted with samples collected in the teaching hospital “Le Scotte” of Siena (Italy). Waters samples were analyzed by: i) ScanVIT method after treatment with acids; ii) ScanVIT method after heating; and iii) cultural standard method after heating. The results of the decontamination procedures and the detection methods were evaluated by comparing the number of Legionella-positive and –negative samples, and the recovery rates (CFU l-1) obtained by ScanVIT and the standard method. Results. We find that ScanVIT method is highly sensitive with both decontamination treatments, yielding a higher recovery of L. pneumophila compared to the standard method. Conversely, ScanVIT associated with the acid-treatment yielded the highest recovery of L. non-pneumophila. Conclusions. The acid-treatment combined to the ScanVIT method increases the recovery of L. nonpneumophila in water samples compared to both ScanVIT associated with heat-treatment and standard culture method. Thus, this method may represent the best choice to detect L. non-pneumophila in water samples and reduce the risk of infection due to underestimation of Legionella loads.