Prevalence of Mastitis, Bacteriological Identification, and Antibiogram of Staphylococcus aureus From Subclinically Infected Lactating Cows in Tocha and Essera Districts, Dawuro Zone, Southwest Ethiopia

Staphylococcus aureus is a common cause of subclinical mastitis, which has got drug resistance and poses a major threat to public and animals. Inappropriate use of drugs, consumption of raw milk, and lack of updated and published scientific work were out of major problems. A cross-sectional study was conducted to assess the occurrence of mastitis, and isolate, identify, and assess antimicrobial susceptibility pattern of S. aureus from subclinically infected lactating cows in Tocha and Essera districts of Dawuro Zone from January-November 2024. Questionnaire survey, clinical examination, California mastitis test, bacteriological identification, and antimicrobial susceptibility testing were conducted. About 384 cows were selected using a simple random sampling method. The overall prevalence of mastitis was 33.60% (129/384), of which 5.73% (22/384) and 27.86% (107/384) were clinical and subclinical mastitis, respectively. Breed (p = 0.007, AOR = 1.985), lactation period (p ≤ 0.001, AOR = 3.021, and p = 0.030, AOR = 1.872), and previous history of mastitis (p = 0.018, AOR = 1.804) significantly associated with subclinical mastitis. The overall prevalence of S. aureus in subclinical mastitis was 35.5% (38/107). About 92.1%, 89.47%, 86.84%, 81.57%, and 78.95% of S. aureus isolates were susceptible to cotrimoxazole (trimethoprim + sulfamethoxazole), kanamycin, streptomycin, sulfisoxazole, and erythromycin, respectively. However, the isolates were highly resistant to penicillin G 100% (38/38) followed by ampicillin 97.37% (37/38), oxacillin 89.47% (34/38), tetracycline 68.42% (26/38), and oxytetracycline 52.63% (20/38). About 5.26% (2/38) (2/38) were multidrug resistant. The high prevalence of subclinical mastitis with high level of drug-resistant S. aureus in raw milk in this study seems dire, a serious challenge for a resilient tomorrow, and is a threat to us all. Thus, regular screening for subclinical mastitis, testing antimicrobials for susceptibility prior to use, and creating awareness to the community to avoid raw milk consumption and the farmers to practice good animal health and management were recommended.