Abstract

Background/Aim: Bovine mastitis, an inflammation of the mammary gland, frequently affects dairy cattle, reducing milk production and causing economic strain on farmers. It is mainly caused by various bacteria, particularly Staphylococcus aureus, which often exhibits resistance to multiple antimicrobials. The excessive use of antibiotics on dairy farms has resulted in the rise of multidrug-resistant (MDR) strains of S. aureus, complicating mastitis treatment. This study was aimed to isolate S. aureus from mastitic cows and evaluate its antimicrobial susceptibility.
Methods: The was conducted from December 2022 to May 2023 in Hawassa City and its surroundings. A total of 172 milk samples from confirmed mastitic cows were cultured using standard bacteriological methods. Forty-four S. aureus isolates were tested against 11 common antimicrobials using the Kirby–Bauer disk diffusion method.
Results: S. aureus was isolated from 51.2% of samples, with significant resistance observed against ampicillin (84.1%), penicillin (81.8%), tetracycline (36.4%), and amoxicillin-clavulanic acid (34.1%). MDR was noted in 43.2% of isolates. In contrast, S. aureus demonstrated complete susceptibility to ceftriaxone and gentamicin (100%), and high susceptibility to streptomycin (88.6%), erythromycin (88.6%), nitrofurantoin (72.7%), and cefotaxime (72.7%).
Conclusion: The significant isolation rate of S. aureus and its MDR underscore the urgent need for enhanced veterinary practices and public health strategies. A comprehensive approach that includes improved management, ongoing education for veterinarians and dairy farmers, responsible antimicrobial usage, and regular monitoring of resistance is essential to tackle the escalating threat of antimicrobial resistance in bovine mastitis.

Key words: Antimicrobial resistance; Bovine; Culture; Ethiopia; Mastitis; Staphylococcus aureus