Isolation of enterococcus in cage birds and determination of antibiotic resistance profiles

Enterococci are commonly found in the gastrointestinal tract of poultry and represent a significant threat to both animal and human health due to their ability to develop multidrug resistance and to harbor virulence genes. This study aimed to isolate and identify Enterococcus spp. from fecal samples collected from cage birds kept in different regions of Istanbul, to determine the phenotypic and genotypic antimicrobial resistance profiles of the obtained Enterococcus species, and to investigate the presence of virulence genes. Between September 2024 and December 2025, a total of 100 fecal samples were collected from cage birds. The samples were transported to the Microbiology Laboratory of the Faculty of Veterinary Medicine, Istanbul University-Cerrahpaşa, under cold chain conditions. Bacterial growth was observed in 66 of the 100 cultured fecal samples, yielding a total of 71 isolates. Of these isolates, 43 were identified as Enterococcus faecalis, 17 as Enterococcus faecium, 6 as Enterococcus gallinarum, and 5 as Enterococcus hirae. Phenotypic antimicrobial resistance rates against ampicillin, vancomycin, teicoplanin, chloramphenicol, ciprofloxacin, erythromycin, enrofloxacin, tylosin, lincomycin/spectinomycin, tetracycline, streptomycin, gentamicin, kanamycin, and clindamycin were determined as 5.63%, 18.31%, 23.94%, 29.58%, 33.80%, 39.44%, 49.30%, 50.70%, 57.75%, 67.61%, 78.87%, 78.87%, 92.96%, and 92.96%, respectively. Multidrug resistance was detected in 69 of the isolates. The vanB resistance gene was detected in 4% of the isolates, whereas vanA, vanC1, vanC2/3, and vanD genes were not detected. Among macrolide resistance genes, ermA was identified in 4% and ermB in 25% of the isolates, while among tetracycline resistance genes, tetM and tetL were detected in 23% and 27% of the isolates, respectively. Regarding virulence genes, gelE, ace, and hyl showed positivity rates of 78.9%, 60.5%, and 21.1%, respectively, whereas esp, agg, and cylA genes were not detected. In conclusion, cage birds in Istanbul were found to constitute an important reservoir for multidrug-resistant Enterococcus bacteria, posing a potential zoonotic risk. These findings highlight the necessity of monitoring antimicrobial resistance in the region and developing appropriate preventive strategies.