Isolation, antimicrobial susceptibility and mecA gene analysis of methicillin-resistant Staphylococcus aureus in Iranian white cheeses

Abstract

The objective of this study was to determine the occurrence of antimicrobial resistance among S. aureus and also to estimate the presence of methicillin-resistance in obtained S. aureus (MRSA) isolates by culture and polymerase chain reaction (PCR) methods. For this purposes, a total of 100 Iranian white and feta cheese samples collected from different sellers were initially evaluated for occurrence of S. aureus by culturing method. The obtained isolates were subjected to disc diffusion antimicrobial susceptibility test, and finally PCR method to detect 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 25 isolates, 23 (92%) were found to be resistant to at least one or more antibiotics tested by 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 strains 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 antimicrobial resistant strains of S. aureus in Iranian cheese samples constitute a potential risk for human health. This calls for better control of cheese contamination sources and as well as the spread of antimicrobial resistant strains.<br><br>Key words: Methicillin-resistant S. aureus (MRSA), Iranian white cheese, PCR