High occurrence of extended-spectrum β-lactamase-producing Salmonella in broiler carcasses from poultry slaughterhouses in South Korea.

The emergence of antibiotic-resistant foodborne Salmonella has become a major public health problem. Consumption of undercooked poultry contaminated with Salmonella can induce food poisoning in humans. In this study, we investigated the occurrence and antibiotic resistance patterns of Salmonella spp. isolated from 120 chicken carcasses produced in 6 poultry slaughterhouses in South Korea. A total of 11 samples (9.2%) were found contaminated with Salmonella: 5 isolates were serotyped as Salmonella Bellevue strain (slaughterhouse C) and 6 isolates were serotyped as Salmonella Enteritidis strain (slaughterhouse E). Salmonella Bellevue isolates were resistant to five antibiotics (ampicillin, chloramphenicol, nalidixic acid, tetracycline, and trimethoprim/sulfamethoxazole), while Salmonella Enteritidis isolates were resistant to nine antibiotics (ampicillin, cefotaxime, ceftazidime, cefazolin, cephalothin, amikacin, nalidixic acid, streptomycin, and tetracycline). All cephalosporin-resistant Salmonella Enteritidis isolates exhibited the extended-spectrum β-lactamase (ESBL) phenotype and carried the gene encoding CTX-M-15, the most prevalent ESBL enzyme worldwide. Based on molecular subtyping performed using the automated rep-polymerase chain reaction (PCR) system (DiversiLab), the isolates showing ≥ 95 similarity in their rep-PCR banding patterns were classified into 5 pulsotypes. Given that cephalosporins are the drugs of choice for invasive Salmonella infections, the high incidence of ESBL-producing strains in chicken should emphasize the necessity of regular monitoring of the occurrence of antibiotic-resistant ESBL-positive Salmonella strains in poultry meat.