Prevalence and characterization of Staphylococcus aureus in two local wastewater treatment plants in Lexington, Kentucky by whole genomic sequencing. Staphylococcus aureus in two local wastewater treatment plants

Infections with Staphylococcus aureus are on the rise in severity and prevalence. Once a disease thought to be spread within the confines of hospitals, staph infections are being spread through contact with the community environment. This study investigated the potential impact of hospital wastes entering municipal sewers and wastewater treatment facilities by determining the prevalence, types, genetic elements, and potential for transmission of S. aureus in these engineered systems. Synchronized sampling events at two wastewater treatment plants were conducted with isolates of S. aureus obtained from the samples by an enrichment method that suppressed the growth of other staph species. DNA was extracted from a subset of the S. aureus isolates, checked by PCR to assure the absence of Staphylococcus epidermidis, and sequenced to determine the multilocus sequence type, spa type, carriage of the methicillin resistance and Panton–Valentine Leucocidin genetic elements, and analyzed for single nucleotide polymorphism differences for pairwise comparison of isolates. The addition of acriflavine to the enrichment and plating media suppressed the growth of S. epidermidis. There were two dominant S. aureus clonal complexes identified in the isolates, one commonly identified as hospital related (CC5) and one community related (CC8). Both types of isolates were found at both treatment facilities, even though only one facility had significant hospital sewage inputs. The presence of S. aureus persisted through treatment, with isolates recovered from the final processes showing genetic diversity in the core genome. The presence of the Panton–Valentine Leucocidin genetic element was greater than expected.