Phenotypic and molecular determination of biofilm formation and antibiotic resistance of coagulase negative staphylococci isolated from food samples of animal origin in Turkey

Aim: This study aimed to investigate the antibiotic resistance and biofilm formation characteristics of the coagulase-negative Staphylococcus (CNS) isolated from various animal food samples (raw milk, cheese, chicken, meat). Methods: A total of 60 Staphylococcus isolates collected from various animal food samples (raw milk, cheese, chicken, meat) were obtained from the frozen culture collection of the Microbiology Laboratory of the Gazi University. The isolates were assessed regarding antibiotic resistance, biofilm and s-layer formation, and biofilm-associated genes. Results: In total, 22 CNS isolates were identified. The CNS isolates were highly resistant to fosfomycin (68.2%; 15/22), fusidic acid (63.6%, n=14/22), and tetracycline (59.1%, n=13/22). There was an intermediate resistance to other antibiotics as well. There was very strong slime production (54.5%, n=12/22) and S-layer production (40.9%, n=9/22). The biofilm formation of CNS isolates was better at 24 hours. Regarding the biofilm-producing genes, 10 (45%) of 22 CNS isolates were positive for the icaA gene, and 4 (18%) isolates were positive for the icaD gene, while all of the isolates were negative for the bap gene. Conclusion: The CNS existing in foods from animals may lead to public health problems with clinical implications as a result of being one of the important factors associated with antibiotic resistance. The bacteria that can gain antibiotic resistance and biofilm formation capabilities in the stages of production and consumption may be a critical healthcare issue for humans and animals.