Molecular characterization and antimicrobial-resistance gene profile of Staphylococcus aureus strains isolated from ovine mastitis in Jordan.

Abstract

Background and aim: Ovine mastitis, particularly subclinical mastitis caused by Staphylococcus aureus, poses significant economic and health challenges in livestock management. This study aimed to investigate the molecular characteristics and antimicrobial-resistance gene profiles of S. aureus isolated from subclinical mastitis in northern Jordan and assess the zoonotic potential of these isolates.

Materials and methods: A total of 283 milk samples from ovines and 24 nasal swabs from animal handlers across three northern Jordanian governorates were analyzed. Bacterial isolates were identified phenotypically and genotypically, with antimicrobial susceptibility tested using disk diffusion and minimum inhibitory concentration assays. The presence of antimicrobial-resistance genes (ARGs) was analyzed through polymerase chain reaction, and genetic relatedness was determined using pulse-field gel electrophoresis (PFGE) and spa typing.

Results: S. aureus was detected in 16 (6%) ovine milk samples and four nasal swab samples from animal handlers. High resistance rates were observed for penicillin G, oxacillin, and cefoxitin (25% each). ARGs, including mecA, blaZ, aph(3')-III, and ant(4')-Ia, were detected in 25% of isolates. PFGE revealed a high genetic similarity among isolates, while spa typing identified three types, with t1534 predominating (81.25%). Limited cross-transmission between ovines and handlers was noted.

Conclusion: The study highlights spa type t1534 as the dominant genotype in ovine mastitis in Jordan and underscores the low zoonotic transmission risk from ovines to animal handlers. The findings emphasize the importance of antimicrobial stewardship and enhanced mastitis management strategies.