Characterisation of methicillin resistant S. aureus strains and risk factors for acquisition in a teaching hospital in northeast India

Purpose: A point prevalence study was carried out in a teaching hospital in Assam to characterise S. aureus strains, establish the rate of colonisation of methicillin resistant S. aureus (MRSA) and associated risk factors for its acquisition. Materials and Methods: Antibiogram-Resistogram profile was done by BSAC standardized disc sensitivity method; Phage and RFLP typing were carried out by the PHLS, London. Results: Single MRSA strain resistant to multiple classes of anti-staphylococcal antibiotics dominated the hospital. The MRSA colonisation rate was found to be 34% (n=29) and 18% (n=80) in orthopaedics and surgery, respectively and only ~1% (n=73) in the medical units. Exposure to ciprofloxacin and surgery were risk factors but duration of hospital stay was not. In contrast, meticillin sensitive S. aureus (MSSA) strains were usually distinct strains and sensitive to most of the anti-staphylococcal antibiotics including 18% to penicillin. Conclusions: The MRSA strain prevalent in the hospital phenotypically resembles the predominant Asian strain viz., Brazilian/Hungarian strains (CC8-MRSA-III). Duration was not a risk factor, which suggests that in absence of exposure to specific antimicrobials, even in a hospital with no or little infection control intervention, a vast majority remain free from MRSA. This underlines the importance of rational prescribing empirical antibiotics.