Purpose: The objective of this research was to isolate S. aureus from Minas frescal cheese processing plants in organic and conventional production and to analyze possible resistance to antibiotics.
Methods: Samples from cheese, raw milk, and the processing chain environment (floor, surfaces, foodhandlers) from three organic and three conventional dairies were collected. For detection of coagulase-positive staphylococci (CPS), the samples were incubated on Baird Parker agar (35°C/48 h), followed by performance of catalase, Gram stain, and coagulase tests.
Results: One hundred fifty-one CPS were isolated; 83 from organic and 68 from conventional dairies. The PCR species confirmation identified 73 S. aureus; 34 from organic and 39 from conventional dairies. The antibiogram was performed for 39 strains identified as S. aureus, 31 strains from organic dairy products, and eight strains from conventional dairy products. Fifteen strains were sensitive to all the antibiotics. All of the strains were sensitive to the chloramphenicol, seven strains showed simultaneous resistance to oxacillin and cefoxitin (four organic and three conventional), suggesting that they are MRSA. Resistance was observed in organic dairies to penicillin (n=15), gentamicin (n=3), tobramycin and erythromycin (n=5), tetracycline (n=2), and clindamycin (n=6). In conventional dairies resistance to penicillin (n=4), tobramycin and erythromycin (n=1), tetracycline (n=1), and clindamycin (n=1).
Significance: The data collected in the research presented showed that more than half of the strains of S. aureus were resistance to some type of antibiotic, with food being a carrier of resistant bacteria capable of causing disease in consumers.