Role of the house fly, Musca domestica L., in dissemination of antibiotic resistant and virulent enterococci from wastewater treatment facilities

House flies and biosludge from four wastewater treatment facilities (WWTF) in northeastern Kansas were sampled for culturing enterococci. Enterococci were quantified, identified, and screened for antibiotic resistance and virulence by phenotypic and genotypic analysis. The profiles of enterococci (diversity, antibiotic resistance and virulence) from WWTF biosludge and the house fly digestive tract were similar, indicating that the flies successfully acquired the bacteria from the substrate. Of twelve antibiotics screened, enterococci were most commonly resistant to tetracycline, quinupristin/dalfopristin, doxycycline, erythromycin and gentamicin. No enterococcal isolates were resistant to vancomycin, tigecycline or linezolid. The greatest amount of enterococci with antibiotic resistance and virulence factors (gelatinase, cytolysin, enterococcus surface protein, and aggregation substance) originated from the WWTF that processed meat waste from a nearby commercial sausage plant, suggesting an agricultural rather than human/clinical source of the isolates. Based on our current data, the management of house flies at WWTF is clearly warranted to prevent dissemination of antibiotic resistant and potentially virulent enterococci to the surrounding environment.