PCR-mediated identification of Methicillin and Vancomycin resistant genes in Staphylococcus aureus strains isolated from the nasal cavity

Abstract

Staphylococcus aureus is colonized in the human nasal cavity and would contaminate hospital and therapeutic environments. This bacterium has a genetic diversity in terms of resistance to antimicrobial agents. Therefore, the purpose of this study was identificatied of Methicillin and Vancomycin resistant genes in Staphylococcus aureus strains which has been isolated from the nasal cavity. 189 patients referred to Amol city health center were sampled. Staphylococcus aureus identification was performed by standard methods. Resistance to antibiotics of Vancomycin, Methicillin, Cefpime, Ceftriaxone, Cefixime, nalidixic acid, Cefazolin, Stiffenoxime, Cefotaxime, Ceftazidime, Imipenem and Ciprofloxacin were identified by disk diffusion method and recommendations of the Laboratory and Clinical Standardization Organization (CLSI). Polymerase chain reaction was performed to detect mecA, vanA and femB genes. 32.2% of the patients were carriers of Staphylococcus aureus in their nose. In this research, 68.85% of the isolates were resistant to Methicillin. 100% resistance to Cefixime and Nalidixic acid antibiotics was observed. Subsequently, the highest amounts of resistance belonged to Cefazolin (96.72%) and Cefepime (86.88%). Resistance to Vancomycin was 70.49%. The lowest amounts of resistance were observed in the two antibiotics Ciprofloxacin and Imipenem, with incidences of 6.55% and 9.83% in isolates, respectively. Genetically, no resistance was observed for Vancomycin and none of the tested isolates were carried vanA gene. Of 61 separated Staphylococcus aureus, 77.04% of them carried mecA gene and 90.16% of them had femB gene. This study showed that the main resistance to Penicillin, Oxacillin and Methicillin in Amol city is due to mecA and femB genes.