Molecular Characterization and Antibiotic Susceptibility Pattern of Methicillin-Resistant S. aureus (MRSA) in Tertiary Care Hospital, Kashan

Methicillin resistant Staphylococcus aureus (MRSA), which is the most common cause of nosocomial infection, has been a major cause of morbidity and mortality around the world. This study was carried out to find out the resistance pattern and staphylococcal cassette chromosome mec (SCCmec) typing among MRSA. This descriptive work was done on 87 Methicillin resistant Staphylococcus aureus isolates which were collected from the patients with infections in a teaching hospital in Kashan, Iran, during the period of 2009. The isolates were tested for antibiotic resistance by the disc-diffusion method, covering 10 antimicrobials. The genotypes of SCCmec subtypes were determined by multiplex PCR. Amomg 87 MRSA isolated tested; the highest resistance was shown against erythromycin, clindamycin, sulfamethoxazole-trimethoprim, and tetracycline respectively. By contrast, the highest sensitivity was shown to amikacin. All of the isolates were resistant to Beta-lactams. All of the isolates were resistant to at least three classes of antibiotics, and all of the isolates were sensitive to vancomycin. Three (3.4%) MRSA strains were SCCmec type I, 12 (13.8%) were type II, 8 (9.2%) were type IV-b, 4 (4.6%) were type IV-d, and 3 (3.4%) were typeV. Overall, 57 (65.5%) MRSA strains could not be typed. The rising trend of multi-resistance to antibiotics poses an alarming threat to treatment of MRSA infections. Our findings show that clinical isolates of MRSA in our hospital carrying various kinds of staphylococcal cassette chromosome mec (SCCmec) types. SCCmec typse II and IV were the predominant strain of MRSA identified.