Genetic diversity of Staphylococcus aureus isolated from hospital wastewaters: spa types t747 and t790 are a serious threat.

Hospital wastewater is often a reservoir for multidrug-resistant organisms and clinically significant pathogens such as MRSA. In this cross-sectional study, 90 Staphylococcus aureus isolates recovered from hospital wastewater were comprehensively characterized. The analysis included antimicrobial susceptibility testing, assessment of biofilm formation, spa typing, and PCR-based detection of a wide panel of antibiotic resistance genes as well as key virulence factors. Our results showed that 43.3, 36.7, and 20% of isolates were classified as strong, intermediate, and weak biofilm-forming strains, respectively. Our data indicated that the resistance profile of aac (6')-Ie/aph (2″), msr(A) (8.9%) was the most prevalent pattern. Spa typing revealed that the 90 isolates belonged to 11 particular spa types, including t747 (16.7%), t790 (14.4%), t10795 (13.3%), t005 (11.1%), t044 (7.8%), t030 (7.8%), t037 (7.8%), t008 (6.7%), t421 (5.6%), t860 (4.4%), and t388 (4.4%). All of the VISA and VRSA strains belonged to SCCmec IV/t790 isolates. Among the 39 strong biofilm producers, the majority (28.2%) belonged to SCCmec IV/t790. The mupirocin-resistant strain belonged to the SCCmec IV/t790 (41.2%), SCCmec III/t037 (17.6%), SCCmec IV/t008 (17.6%), SCCmec III/t030 (11.8%), and SCCmec IV/t044 (11.8%) isolates. These findings highlight the value of wastewater surveillance for tracking antimicrobial resistance and guiding public health interventions.