Resistance profiling and molecular characterization of Staphylococcus aureus isolated from goats in Korea

Staphylococcus aureus is among the most common zoonotic pathogens that cause foodborne illnesses worldwide. The main objectives of the current study were therefore to determine the antimicrobial susceptibility profiles of S. aureus isolated from goats in Korea and to investigate the molecular characteristics of identified methicillin-resistant S. aureus (MRSA). In the study, 481 S. aureus isolates (431 from the nasal cavity and 50 from carcass) were recovered from 1146 carcasses and nasal swabs between July 2018 and January 2019. Approximately 82% and 72.6% of nasal and carcass isolates, respectively, were resistant to at least one antimicrobial agent, with the highest rate of resistance to penicillin, followed by resistance to chloramphenicol and tetracycline. Relatively small proportions of the isolates were resistant to cefoxitin, clindamycin, and erythromycin. However, all S. aureus isolates were sensitive to linezolid, rifampin, and vancomycin. Six MRSA isolates were obtained, three each from the nasal cavity and carcass. MRSA isolates were of two sequence types (ST) (ST72 and ST398), three spa types (t664, t324, and t571), and two SCCmec types (IV and V). The ST72 MRSA isolates had identical PFGE profiles. In addition, ST72 MRSA-SCCmec IV isolates carried at least six staphylococcal leukotoxin- and enterotoxin-encoding genes (lukED, seg, sei, sem, sen, seo, and seq). The remaining ST398 isolate carried only the lukED gene and was additionally resistant to eight non-β-lactam antibiotics. To the best of our knowledge, this is the first report of MRSA from goats in Korea. There is a possibility of transmission of MRSA from goat to human or contamination of food products. Therefore, regular microbiological investigation in goats, farms, and slaughterhouses is critical to determine the existence of virulent and multi-drug resistant (MDR) S. aureus and to implement preventive strategies.