Staphylococcal Cassette Chromosome mec Typing of Meticillin-Resistant Staphylococcus aureus in Kermanshah Province, West of Iran

 Methicillin-resistant Staphylococcus aureus (MRSA) isolates are important agents of human bacterial infections. The mecA gene as the main cause of resistance against beta-lactams is located in genetic elements which are known as staphylococcal cassette chromosome mec (SCCmec).

 The research aimed to evaluate the antibiotic susceptibility pattern and SCCmec typing of MRSA isolates in Kermanshah Province, West of Iran.

 Identification of MRSA isolates were done using phenotypic and genotypic methods. Antimicrobial susceptibility patterns were determined using the disk diffusion method and minimum inhibitory concentration (MIC) testing by agar dilution method. The SCCmec types of isolates were identified using PCR method. The results of the research were analyzed using SPSS.V16 software.

 In this research, of 146 isolates, 126 isolates were confirmed as S. aureus using phenotypic methods and PCR analysis of femB gene. All isolates were sensitive to vancomycin by both

disk agar diffusion and MIC testing by agar dilution method. The highest resistance rate was related to erythromycin (75.4%) and ciprofloxacin (73%). Of 126 S. aureus isolates, 83 cases (65.9%) and 81 cases (64.3%) were MRSA based on the existence of mecA gene and cefoxitin diffusion disk test, respectively. There was a statistically significant difference in antibiotic susceptibility pattern of MRSA and methicillin susceptible Staphylococcus aureus (MSSA) isolates for some antibiotics such as gentamicin, amikacin, erythromycin, ciprofloxacin, and linezolid (P < 0.05). SCCmec types were detected as 20 cases (24.1%) type I, 5 cases (6%) type II, 37 cases (44.6%) were type III (the most prevalent type), 6 cases (7.2%) type IVa, and 3 cases (3.6%) type IV. The prevalence of HA-MRSA (types I, II, and III) and CA-MRSA (types IV and V) in this study were 74.7% and 10.8%, respectively.

 The prevalence of MRSA isolates is high in Kermanshah Province, West of Iran. The cefoxitin diffusion disk testing could be considered a simple, cheap and reliable test for identification of MRSA isolates in all laboratories. The most frequent type of SCCmec is type III. These findings could be due to an increase in antibiotic consumption and insufficient infection control systems.