Abstract
<title>Abstract</title> <p>Background Bovine mastitis is a major production disease affecting dairy cattle worldwide, with Staphylococcus aureus being one of the most common etiological agents. The emergence of methicillin-resistant S. aureus (MRSA) poses significant public health and economic concerns. This study aimed to isolate methicillin-resistant Staphylococcus aureus from mastitic milk samples and determine the antimicrobial resistance patterns of S. aureus isolates in dairy farms around Sebeta town, Ethiopia. Methods A cross-sectional study was conducted from December 2017 to March 2018 in and around Sebeta town. A total of 200 lactating dairy cows were examined for mastitis using the California Mastitis Test (CMT). Milk samples were collected aseptically from CMT-positive quarters and cultured for bacterial isolation. S. aureus isolates were identified using standard microbiological techniques including Gram staining, catalase test, coagulase test, and the OMNILOG identification system. Antimicrobial susceptibility testing was performed using the disc diffusion method against ten antimicrobial agents. Results The overall prevalence of mastitis was 65% (130/200). S. aureus was isolated from 23 (17.69%) of the mastitic milk samples. Antimicrobial susceptibility testing revealed that the isolates were highly resistant to penicillin G (91.3%) and ampicillin (91.3%), with moderate resistance to oxytetracycline (39.1%). All isolates (100%) were susceptible to vancomycin, oxacillin, gentamycin, and cefoxitin. High susceptibility was observed for erythromycin (95.7%), sulphamethoxazole/trimethoprim (95.7%), and methicillin (95.7%). Multidrug resistance was observed in 91.3% of the isolates, with 47.82% showing resistance to both penicillin G and ampicillin, and 43.47% showing resistance to penicillin G, ampicillin, and oxytetracycline. Conclusions This study demonstrated a high prevalence of bovine mastitis in the study area, with a considerable proportion of S. aureus isolates showing resistance to commonly used antimicrobials. Although MRSA was not prevalent in this study population, the presence of multidrug-resistant S. aureus in milk samples is alarming and warrants continuous surveillance and prudent antimicrobial use in dairy farms.</p>