Evaluation of aminoglycoside modifying enzymes, SCCmec, coagulase gene and PCR-RFLP coagulase gene typing of Staphylococcus aureus isolates from hospitals in Shiraz, southwest of Iran

Abstract

<i>Staphylococcus aureus</i> is an important human pathogen that causes various infections. Aminoglycosides are broad-spectrum antibiotics used to treat methicillinresistant <i>S. aureus</i> (MRSA) infections. Typing of <i>S. aureus</i> isolates by coagulase gene typing and PCR-RFLP <i>coa</i> gene is a fast and suitable method for epidemiological studies. Aim of the present study was to evaluate the resistance to aminoglycosides, staphylococcal chromosomal cassette mec (SCCmec) types, coagulation typing and PCR-RFLP <i>coa</i> gene in clinical isolates of <i>S. aureus</i>. 192 <i>S. aureus</i> isolates were collected from Namazi and Shahid Faghihi hospitals. Antibiotic resistance was measured by disk diffusion method and MIC was determined for gentamicin. The presence of genes encoding aminoglycoside modifying enzymes (<i>AME</i>) and <i>mecA</i> gene were assessed by PCR. Also the coagulase typing, PCR-RFLP <i>coa</i> gene, and SCCmec typing were performed. Out of 192 isolated <i>S. aureus</i> isolates, 83 (43.2%) MRSA isolates were identified. In this study, a high resistance to streptomycin and gentamicin (98.7%) were observed. Among the <i>AME</i> genes, the <i>aac (6')-Ie-aph (2″)</i> gene was the most common. Based on the SCCmec typing, it was determined that the prevalence of SCCmec type III (45.8%) was highest. From the amplification of the <i>coa</i> gene, 5 different types were obtained. Also, in digestion of <i>coa</i> gene products by <i>HaeIII</i> enzyme, 10 different RFLP patterns were observed. According to this study, aminoglycoside resistance is increasing among MRSA isolates. As a result, monitoring and control of aminoglycoside resistance can be effective in the treatment of MRSA isolates. Also, typing of <i>S. aureus</i> isolates based on <i>coagulase</i> gene polymorphism is a suitable method for epidemiological studies.