Molecular characterization of methicillin-resistant Staphylococcus aureus from bovine mastitis and human contacts in Jordan

Methicillin-resistant Staphylococcus aureus (MRSA) infection has a significant impact on public health. Therefore, this study investigates the occurrence of MRSA isolated from cows with subclinical mastitis in Jordan during the period from January 2021 to December 2023. It is also to compare their genotypic and phenotypic characteristics with those of isolates from their associated human strains. To achieve this objective, milk samples were collected aseptically and cultured on mannitol salt agar and blood agar. The isolates were identified based on colony morphology, biochemical tests, and PCR confirmation targeting the nuc and mecA genes. In addition, molecular-based typing techniques (MLST and spa typing) have been applied and supplemented by antimicrobial susceptibility testing. A total of 310 bovine S. aureus isolates were identified, of which 52 (16.8%) were MRSA. Besides that, 49 and 33 MRSA strains were isolated from people related to and unrelated to these animals, respectively. Antimicrobial susceptibility testing revealed high resistance rates to β-lactams, macrolides, and tetracyclines. Nine distinct spa clusters and 21 different spa types were observed. The most prevalent spa type among the isolates was t386 (38%, n=17). For the first time, two novel spa types were discovered among the isolates examined in this study. The cluster pattern of spa isolates indicates a possible close relationship between human and animal isolates.