Cassette chromosome mec typing of methicillin-resistant Staphylococcus aureus isolates from patients in Tehran

Methicillin-resistant Staphylococcus aureus is the cause of nosocomial infections leading to high mortality. Since these strains have become prevalent in the world, it is necessary to identify and type them. This cross-sectional study was conducted to study a total of 1475 clinical specimens from Iranian patients in 2012-2013. Using phenotypic tests such as Gram stain, catalase, coagulase, DNase and mannitol fermentation 169 isolates of Staphylococcus aureus and by utilizing methicillin-resistance test 100 MRSA isolates were identified. SCCmec typing was performed by multiplex PCR method and the results were analyzed using chi-square tests by SPSS-18 software. Disk agar diffusion test using cefoxitin disk (30 mu g) showed methicillin resistance in 59% of our isolates. mecA and femB genes were identified in all of the MRSA isolates using PCR method. Frequency of SCCmec types and sub-types were as follow; SCCmecIII (77%), SCCmecI (5%), SCCmecIVa (1%), SCC-mecIVc (1%), Mixed isolates SCCmecIVc-III (1%) and Non typeable isolates (15%). Non typeable isolates recovered in two groups (10% without any band and 5% of multi-bands III-I). In this study, 82% of isolates were HA-MRSA, 3% were CA-MRSA and 15% were Non typeable. In our S. aureus isolates methicillin resistance was 59%. The most frequent SCCmec type was SCCmecIII (77%). Our results demonstrated the spread of HA-MRSA isolates in the community and propagating CA-MRSA isolates in the studied hospitals.