Cassette Chromosome mec Typing of Methicillin-Resistant Staphylococcus aureus Isolates Collected from Sina and Imam Reza Hospitals of Tabriz

Backgrounds and

Methicillin-resistant Staphylococcus aureus is a 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 specimens collected from patients of Imam Reza and Sina hospitals of Tabriz 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 using SPSS-18 software.

Disc agar diffusion test using cefoxitin disc (30 µg) 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%), SCCmecIVc (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, the prevalence of 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.