Methicillin-resistant Staphylococcus aureus: prevalence, incidence and risk factors associated with colonization in Sri Lanka.

We studied the prevalence of and risk factors for nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) on admission and the incidence and risk factors for nosocomial acquisition of MRSA in a 60 bed, male surgical unit in the National Hospital of Sri Lanka (NHSL). Nasal swab cultures were obtained from 271 patients admitted for routine surgery within 36 h of admission and repeated every other day until discharge. Clinical and epidemiological risk factors for colonization were compared between patients with MRSA at the time of admission or colonized after admission, and patients who were not colonized. MRSA was isolated from 35 patients (12.9%) with 20 (7.4%) colonized on admission and 15 (6%) acquiring MRSA after admission. Hospitalization within the previous year, antibiotic use within the previous two months, and transfer from another ward within the NHSL were associated with colonization with MRSA on admission. Risk factors for nosocomial acquisition of MRSA were the prophylactic and empiric use of antibiotics. The duration of antibiotic use and the duration of stay in hospital were significantly longer in patients who acquired MRSA. MRSA surveillance and control programmes in this unit would be more cost-effective if targeted at patients with these risk factors.