Determination of the Ampicillin–Resistant Enterococcus strains, antibiotic resistance and virulence genes in raw milk and chicken meat samples from Sivas province, Türkiye

The object of this study was to determine the occurrence of ampicillin–resistant (AmpR) Enterococcus spp. isolated from raw milk and chicken (Gallus gallus domesticus) meat samples focus on their antimicrobial resistance profiles and virulence genes from Sivas province, Türkiye. A total of 210 samples comprising raw milk (n = 150; cow (Bos taurus), sheep (Ovis aries) and buffalo (Bubalus bubalis) milk) and fresh chicken pieces (n = 60; thighs and wings with skin) were collected and analyzed. Antimicrobial susceptibility testing was performed using the disk diffusion method, while minimum inhibitory concentrations for AmpR isolates were determined by broth microdilution. Polymerase chain reaction identified the isolates at the species level and screened for key virulence genes (asa1, cylA, esp, gelE and hyl). A total of 40 strains of AmpR Enterococcus spp. were isolated from raw milk and chicken meat samples. Out of the isolates from raw milk and chicken meat, 67.5% were identified as E. faecium, 12.5% as E. faecalis, and 20% as other Enterococcus species. Among the AmpR Enterococcus spp. isolates, minimum inhibitory concentration values ≥ 16 μg·mL-1 were detected in 25.0% of isolates from milk and 30.0% of isolates from chicken meat samples. Disk diffusion revealed varied resistance among isolates, with the highest against erythromycin (55.0%) and tetracycline (50.0%), followed by rifampin (42.5%), ciprofloxacin (20.0%), vancomycin (12.5%), gentamicin (10.0%), and chloramphenicol (7.5%). AmpR Enterococcus spp. isolates exhibited a multidrug resistance rate of 67.5%. Virulence gene analysis indicated the presence of the asa1 gene in only one E. faecalis isolate (2.5%), while cylA, esp, gelE and hyl genes were not detected. Detection of antibiotic–resistant Enterococcus spp. in raw milk and chicken meat, and occurrence of vancomycin and gentamicin resistant enterococci are noteworthy for public health concerns. Monitoring the antimicrobial–resistant enterococci in animal–derived foods is crucial within the framework of the One Health concept.