Typing of Methicillin Resistant Staphylococcus aureus Strains Isolated from Patients in Isfahan

Staphylococcus aureus is a common cause of infection among human and animals and known as community - acquired and nosocomial pathogen. Most of the isolates contain lysogenic phages which are responsible for production of various vir ulence factors. Methicillin resistance in S. aureus is related to mecA gene. mecA gene, it’s regulatory genes, resistance genes to other antibacterial agents and recombinase enzyme gene locus (ccr) are located on staphylococcal cassette chromosome (SCCmec). The aim of this study was to analyze the antibiotic resistance pattern, and typing of mecA gene cluster and ccr gene locus of MRSA strains isolated from patients in Isfahan from 2012 - 2013. Totally 293 Staphylococcus aureus isolate s were collected from 1 hospital in Karaj. All isolates were identified at the species level using specific primers. Susceptibility to 15 antibiotics was determined using disc diffusion method according to guidelines of Clinical Laboratory and Standard ins titute (CLSI). Minimum inhibitory concentration (MIC) of oxacillin and vancomycin in MRSA isolates were also detected using broth micro dilution assay according to CLSI recommendation. Primers for identification of 6 classes of prophages were used in a Mul tiplex - PCR assay. mecA gene was detected using specific primers. Multiplex - PCR assays were used for ccr and SCCmec typing. Among S. aureus isolates, 101 strains (34.5%) were selected as MRSA. The highest antibiotic resistance was observed to eryt hromycin (88%) and followed by ciprofloxacin (85%), clindamycin (84%) and tobramycin (81%) respectively. None of the isolates were resistant to vancomycin, linezolid and synercid. High (MIC≥128 μg/ml) level resistance to oxacillin was observed in 70% of th e isolates. Two different prophage types and 2 sub - types were found in MRSA isolates. All isolates contained mecA gene and 100% of MRSA isolates harbored SCCmecc type III and also type 3 ccr. High prevalence of different classes of prophages e ncoding a variety of virulence factors and high oxacillin resistance provide an important role for phages in the evolutionary development of virulence factors and also diversity in methicillin resistance cassette in MRSA isolates. The presence of SCCmec ty pe III indicating the high prevalence of hospital acquired MRSA isolates. Prevalence of these highly virulent isolates with high resistance to first and second lines of treatments is a potential treat for public health.