Prevalence and antimicrobial susceptibility pattern of methicillin-resistant Staphylococcus aureus in Assam

Methicillin-resistant Staphylococcus aureus (MRSA) has become a serious problem in intensive care units, because of development of multiresistance, and also intrinsic resistance to beta-lactam antibiotics. The present study was carried out to investigate the prevalence of MRSA and their rate of resistance to different antistaphylococcal antibiotics.

Between January 2007 and February 2008, the clinical specimens submitted at the microbiology laboratory were processed and all S. aureus isolates were included in this study. All isolates were identified morphologically and biochemically by standard laboratory procedures and antibiotic susceptibility pattern was determined by modified Kirby Bauer disc diffusion method.

Methicillin resistance was observed in 34.78% of isolates, of which 37.5% were found to be resistant to all commonly used antibiotics. In MRSA isolates, 50% had constitutive resistance, 9.38% had inducible MLS(B) resistance and 18.75% had MS phenotype.

There is a progressive increase in MRSA prevalence in the country but the present rate is still low in comparison to values found in some other institutes. The rate of inducible MLS(B) resistance was also lower in comparison with findings from other parts of the country.