Genetic variation and antibiotic susceptibility among Staphylococcus aureus isolates from dairy products and food handlers

A total of one hundred and seventeen isolates of Staphylococcus aureus were obtained from different dairy products and nasal mucosa of cheese factory workers in the state of Jalisco, Mexico. The isolates were characterized by their sensitivity to different antibiotics, while genetic diversity was analyzed by Box-PCR molecular marker. Approximately half (45%) of the isolates analyzed showed antimicrobial resistance properties to at least one of the antibiotics tested. Cheese isolates were resistant to oxacillin (29%), tetracycline (28%), clindamycin (21%), erythromycin (18%), gentamicin (4%), and vancomycin (2%). All milk isolates were resistant to tetracycline, while the anterior nares samples were resistant to tetracycline and erythromycin. The dendrogram obtained by Box-PCR generated 19 groups, with two of these groups containing 62% of the isolates. The results showed that the S. aureus isolates of dairy products have a high genetic variability with elevated resistance to oxacillin, clindamycin and tetracycline. This study presents valuable epidemiological information that contributes to the development of strategies for controlling contamination of dairy products.