Characterization of Methicillin-Resistant Staphylococcus aureus (MRSA) in Dairy Products from Local Farms in Lagos

Abstract

Staphylococcus aureus, a coagulase-positive Gram-positive bacterium, is a major foodborne pathogen commonly associated with raw milk and dairy products, causing food poisoning and mastitis in dairy cattle. Methicillin-resistant Staphylococcus aureus (MRSA) strains present significant public health risks due to their resistance to common antibiotics. This study aimed to investigate the prevalence and antimicrobial resistance profile of S. aureus in raw cow milk from Lagos State, Nigeria. A total of 132 raw milk samples were collected from cattle farms in Kara, an abattoir in Agege, Lagos. Out of 114 bacterial colonies, 64 were Gram-positive cocci, and 17 isolates (14.9%) were identified as S. aureus using cultural and biochemical methods. Antimicrobial susceptibility testing revealed that all S. aureus isolates were resistant to methicillin, 5 (29.4%) were resistant to cefoxitin, 1 (5.9%) was vancomycin-resistant, and all 17 (100%)  were susceptible to imipenem. Broth microdilution testing showed cefoxitin MIC values of ?4??g/mL for the five resistant isolates, confirming MRSA status. PCR amplification further detected the mecA gene in these isolates, supporting phenotypic resistance findings. The prevalence of S. aureus was higher in Kara (58.9%) compared to Agege (41.1%). The findings of this study highlight the significant presence of antibiotic-resistant S. aureus in raw milk, which poses health risks to consumers and emphasizes the need for enhanced surveillance, antibiotic stewardship, and public education on milk safety.