Qualitative assessment of virulence and resistance gene transcripts in Staphylococcus aureus isolated from buffalo...

Staphylococcus aureus is a major foodborne pathogen capable of producing enterotoxins and exhibiting antimicrobial resistance, posing a significant risk to public health through contaminated dairy products. This study investigated the occurrence of S. aureus isolates recovered from buffalo milk and dairy products, along with the potential presence of selected virulence and resistance gene transcripts. A total of 100 samples, including raw buffalo milk, cream, and cheese, were analyzed using classical microbiological methods. Isolates were characterized phenotypically, and methicillin resistance was assessed by disk diffusion. The potential presence of gene transcripts of nuc, mecA, pvl, and classical enterotoxin genes (sea, seb, sec, and sed) were evaluated using RT-qPCR. Despite DNase I treatment, clear gene-specific melting peaks, and early cycle thresholds, results were interpreted cautiously to account for potential genomic DNA amplification due to the lack of no-reverse-transcriptase (NRT) controls. S. aureus was recovered from 12% of the samples, with the highest recovery observed in cheese. A total of 21 S. aureus isolates were obtained and further characterized. All isolates exhibited amplification corresponding to pvl and at least one enterotoxin gene, with sec-related signals being the most frequently detected. Phenotypic testing classified 61.9% of the isolates as methicillin-resistant based on cefoxitin disk diffusion, while mecA gene amplification were detected in 71.4% of the isolates. These findings suggest that S. aureus isolates recovered from buffalo dairy products, particularly traditionally produced cheese, may carry virulence- and resistance-associated genetic features of potential public health relevance. The combined phenotypic and screening approach used in this study provides additional insight into potential food safety concerns associated with buffalo-derived dairy products.