Risk factors and mortality of nosocomial infections of methicillin-resistant Staphylococcus aureus in an intensive care unit

Abstract

Purpose Methicillin-resistant Staphylococcus aureus (MRSA) infections are an increasing worldwide problem. We determined risk factors and predictors of mortality of MRSA nosocomial infections (NIs). Materials and Methods A prospective cohort study was performed in an adult mixed medical and surgical intensive care unit from 2003 to 2007. Stratified analyses and generalized linear modeling were used to assess risk factors and predictors of infection and mortality. Results A total of 184 infections (3.6% of all infections) were due to S aureus, and 97.8% of these were methicillin resistant. The most common infection sites were respiratory tract (35.6%) and bloodstream (30.6%). Stratified analyses of length of stay (LOS) before onset of MRSA NI and death indicated that MRSA infection (odds ratio [OR], 38.49; 95% confidence interval [CI], 25.53-58.09) and mortality (OR, 4.72; 95% CI, 1.92-11.99) were more likely for LOS more than 15 days than for LOS less than 7 days. After controlling for potentially confounding factors by use of generalized linear modeling analysis, we identified the following as independent risk factors: LOS before onset of MRSA infection (OR, 1.03; 95% CI, 0.01-1.04), serum creatinine (OR, 5.87; 95% CI, 1.37-9.21) level, use of mechanical ventilator (OR, 6.71; 95% CI, 1.58-8.5), and central venous catheter (OR, 1.13; 95% CI, 1.05-1.31). Conclusions Methicillin resistance is very common with S aureus infection. In our intensive care unit, use of invasive devices/procedures and LOS were the most important risk factors for infection.