Occurrence of Uncultured Legionella spp. in Treated Wastewater Effluent and Its Impact on Human Health (SCA.Re.S Project)

Wastewater treatment plants (WWTPs) provide optimal conditions for the environmental spread of . As part of the Evaluation of Sanitary Risk Related to the Discharge of Wastewater to the Ground (SCA.Re.S) project, this study was conducted to evaluate the presence of in WWTP effluent and in groundwater samples collected from two wells located downstream from the plant. The samples were analyzed to determine the concentrations of spp using the standard culture-based method and molecular techniques, followed by genomic sequencing analysis. was detected only with the molecular methods (except in one sample of effluent positive for serogroup 6), which showed viable and non- through the use of free DNA removal solution in both the effluent and groundwater, with concentrations that progressively decreased downstream from the plant. Viable appeared to be slightly more concentrated in warm months. However, no significant differences ( ≥ 0.05) in concentrations between cold and warm months were observed. A genotypic analysis characterized the species present in the samples and found that uncultured spp, as yet undefined, constituted the prevalent species in all the samples (range 77.15-83.17%). WWTPs play an important role in the hygienic and sanitary quality of groundwater for different uses. The application of control systems during the purification of effluents is warranted to prevent possible outbreaks of legionellosis.