Prevalence of Methicillin-resistant Staphylococcus aureus in Bovine Subclinical Mastitis in Jos South Local Government Area of Plateau State, Nigeria

This study was carried out to investigate antibiotic resistance pattern of Staphylococcus aureus and determine the prevalence of methicillin-resistant S. aureus (MRSA) in bovine subclinical mastitis (SCM) at dairy farms in Jos South Local Government Area, Plateau State, Nigeria. Three (3) dairy herds who met the inclusion criteria were identified and selected by convenience and using a minimum size calculation, 36 lactating cows were sampled. The cows were selected by a blind random sampling technique. Clinical examination was performed to exclude clinical mastitis (CM) and California mastitis test (CMT) to identify subclinical mastitis (SCM). A total of 142 quarter milk samples were collected for culture enrichment in nutrient broth followed by culture on mannitol salt agar (MSA) for S. aureus isolation and biochemical identification. Antimicrobial susceptibility testing (AST) of the isolates against selected antibiotics was performed by the disk diffusion method. Using R Commander version 3.6.2 data such as cow breed, age, parity, lactation, and management system were collected, and analyzed to determine their relationship with bovine subclinical mastitis. Of the total of 142 quarter milk samples collected from the 36 cows, 43 (30.3%) were positive for subclinical mastitis by CMT in 16 (44.4%) cows, and S. aureus was isolated in 29 (20.4%) of the positive samples, with MRSA from 17 (11.9%). Antibiotic susceptibility test showed resistance of S. aureus to oxacillin (60.7%), cotrimoxazole (46.4%), nalidixic acid (42.8%), ampicillin (39.2%), cefalexin (32.1%), Augmentin (14.7%), gentamicin (10.7%), ciprofloxacin (10.7%), streptomycin (10.7%) and levofloxacin (0%). The result in this study indicates the growing concern in the diary and healthcare industries of Nigeria since the strains of this pathogen is becoming more resistant to commercially available antimicrobials, and this is an alarming concern for both animal and public health. Therefore, public awareness on transmission, prevention and control of methicillin-resistant S. aureus is suggested.