Epidemiology and associated factors for nosocomial methicillin-resistant Staphylococcus aureus infection in a tertiary-care hospital.

We analysed nosocomial MRSA cases between January 2004 and December 2006 in a retrospective case-control study in a 250-bed tertiary-care teaching hospital. During the study period, 265 nosocomial Staphylococcus aureus infections were identified in 231 patients. There was a significant increase in methicillin resistance in isolates (MRSA) from these infections with frequencies for 2004 of 39/88 (44.3%), 2005 (62/80, 77.5%), and 2006 (75/97, 77.3%) (P<0.001). Multivariate analysis showed that associated factors for nosocomial MRSA infection were prolonged hospitalization (OR 3.982, 95% CI 2.235-7.094, P<0.001), mechanical ventilation (OR 3.052, 95% CI 1.666-5.590, P<0.001), surgical operation (OR 2.032, 95% CI 1.102-3.748, P=0.023), and male sex (OR 2.000, 95% CI 1.081-3.699, P=0.027). The determination of associated factors for methicillin resistance in nosocomial S. aureus infections in hospitals will play an important role in efforts to reduce MRSA infection rates.