Prevalence of exfoliative toxin A and B genes in Staphylococcus aureus isolated from clinical specimens

Abstract

The pathogenicity of Staphylococcus aureus is based on the production of various virulence factors. The frequency of these factors can markedly differ according to the geographical region. In this study, we investigated the prevalence of two frequent isoforms of exfoliative toxins and mecA genes using PCR in 197 clinical isolates obtained from clinical samples during the years 2011 and 2012. The samples were obtained from an educational hospital in northern Tehran, Iran. In addition, the antibiotic susceptibility pattern was studied for each isolate using the disc diffusion method. In this study, 186 (94.4%), 15 (7.6%) and 172 (86.3%) of the 197 isolates expressed the eta, etb and mecA genes, respectively. In addition, 164 (88.2%) and 12 (80%) strains, which harbored the eta and etb genes, respectively, were MRSA (methicillin resistant S. aureus). Furthermore, the prevalence of the mecA, eta and etb genes was higher among the wound samples (61.2%, 55.8% and 6.09%, respectively). We observed high rates of MDR (multi drug resistance) among our isolates. A significant correlation was detected between the presence of the mecA gene and the resistance to oxacillin, gentamicin, kanamycin, erythromycin, tetracycline, cotrimoxazole, clindamycin, and cephazolin as well as the multi-drug resistant property (P<0.05). In addition to penicillin, the MDR properties and resistances to the tested antibiotics in the etb-positive strains were significantly lower compared to the etb-negative strains (P<0.05). The prevalence of the eta, etb and mecA genes might be due to the specific geographic region.