Detection of mecA gene and methicillin-resistant Staphylococcus aureus (MRSA) isolated from milk and risk factors from the farmer in Probolinggo, Indonesia

Staphylococcus aureus is commonly found in dairy cows which is a source of contamination in milk. Staphylococcus aureus that is resistant to beta-lactam antibiotics can be said to be Methicillin-Resistant Staphylococcus aureus (MRSA). The spread of MRSA cannot be separated from sanitation management during milking, it can be from milk that is milked from the udder and it can also be from the hands of farmers during the milking process. The purpose of this study was to examine the level of MRSA contamination in dairy cow's milk and farmer's hand swabs. The samples in this study were 109 samples of dairy cow’s milk and 41 samples of farmer's hand swabs taken at a dairy farm in Probolinggo, East Java, Indonesia. Samples were cultured and purified using Mannitol Salt Agar (MSA). The profile of Staphylococcus aureus resistance was carried out by disk diffusion test using a disc of beta-lactam antibiotics, namely Oxacillin and Cefoxitin. The Staphylococcus aureus isolates that were resistant to Oxacillin and Cefoxitin antibiotics were then tested for Oxacillin Resistance Screening Agar Base (ORSAB) as a confirmatory test for MRSA. Staphylococcus aureus isolates suspected of MRSA were then tested genotypically by Polymerase Chain Reaction (PCR) method to detect the presence of the gene encoding mecA. The results of the isolation and identification found 80 isolates (53.33%) of Staphylococcus aureus. The results of the resistance test found that 42 isolates (15%) of Staphylococcus aureus were resistant to Oxacillin and 10 isolates (12.5%) were resistant to Cefoxitin. The ORSAB test found as many as 20 isolates (47.62%) were positive for MRSA. In PCR testing to detect the presence of the mecA gene, 3 isolates (30%) were positive for the mecA gene. This study shows that several Staphylococcus aureus isolates are MRSA and have the gene encoding mecA in dairy farms.