Isolation, antimicrobial susceptibility and mecA gene analysis of methicillin-resistant Staphylococcus aureus

The objective of this study was to determine the occurrence of antimicrobial resistance among Staphylococcus aureus and to estimate the presence of methicillin-resistance in S. aureus (MRSA) isolates obtained by culture and polymerase chain reaction (PCR) methods. For this purposes, 100 Iranian white and feta cheese samples collected from different suppliers were initially evaluated for the occurrence of S. aureus by culturing methods. The obtained isolates were subjected to disc diffusion antimicrobial susceptibility tests and a PCR method to detect the mecA gene. Out of the 100 cheese samples examined, 25 (25%) samples were contaminated with S. aureus with a mean of 5.74 ± 5.67 log cfu/g. Out of the 25 isolates, 23 (92%) were found to be resistant to at least one antibiotic or more, tested by a disk diffusion method. The highest rate of antibiotic resistance was observed to penicillin G (92%) followed by ampicillin (73%) and cloxacillin (68%). None of the isolates was resistant to gentamycin and vancomycin. Eight (34.78%) of the 23 S. aureus isolates were genotypically confirmed as MRSA. The results indicate that the presence of antimicrobialresistant strains of S. aureus in Iranian cheese samples constitute a potential risk for human health. This calls for better control of the spread of antimicrobial resistant strains as well as cheese contamination sources.