Investigation of mecA- and mecC-positive Staphylococcus aureus from raw milk and traditional artisanal dairy foods

The recent emergence of LA-MRSA and their identification in people in contact with livestock has increased their importance for dairy sector and has led to the need to check MRSA presence in dairy foods. Therefore, a total of 285 dairy food samples were analyzed for the presence of MRSA. The 285 samples included raw milk (50 samples), traditional cheeses consisting of white-pickled cheese (50 samples) and Tulum cheese (50 samples), yogurt (25 samples), butter (25 samples), traditional clotted cream (20 samples), pastry cream (50 samples), and traditional Maras ice-cream (15 samples). The isolation procedure of S. aureus followed the EN/ISO 6888–1 (01/2004) method. Out of 99 presumptive isolates, 27 S. aureus isolate were identified by both MALDI-TOF MS and PCR. Overall, 15 out of 285 samples (5.26%) were contaminated by S. aureus; however, mean contamination level of S. aureus between different types of foods was observed as the highest in pastry creams with 6.4 × 103 CFU/g No S. aureus was isolated in yogurt, butter, traditional clotted cream, and traditional Maras ice-cream samples. Strains with MRSA characteristics were investigated by real-time PCR (RTiPCR)-targeting mecA and mecC genes. Out of 27 S. aureus strains, 4 strains carried one gene [mecA gene in 2 strains, isolated from raw milk (sample no: 27) and a White-pickled cheese (sample no: 46); 2 strains carried mecC gene, isolated from two different pastry creams (sample no: 33 and 44)], and only a strain isolated from a pastry cream (sample no: 21) harbored both mecA and mecC genes. None of the strains from Tulum cheeses were positive with either mec genes. This study revealed the relationship of MRSA with raw milk and traditional artisanal dairy products. Extra preventive measures to avoid MRSA-contaminated dairy foods must be applied as their consumption poses a potential risk to public health