Meticillin-resistant Staphylococcus aureus in the intensive care unit: its effect on outcome and risk factors for acquisition

Abstract

Meticillin-resistant Staphylococcus aureus (MRSA) is a common cause of nosocomial infection in the intensive care unit (ICU). A perception exists that ICU-acquired MRSA is associated with poor outcomes, although there are few data to support this. To determine the effect of acquiring MRSA in the ICU on 180-day mortality, and to identify risk factors associated with acquisition. Data were collected prospectively from 2007 to 2013. Patients who remained MRSA negative throughout their ICU admission were matched with patients who acquired MRSA in terms of age, Acute Physiology and Chronic Health Evaluation II score, length of ICU stay and surgical/non-surgical status. In total, 2405 patients were included in the analysis. Patients who acquired MRSA in the ICU had significantly longer ICU stays than patients who were admitted with MRSA and patients who remained MRSA negative throughout their ICU stay (P < 0.001 for both). There were no significant differences in 180-day mortality between the groups (P = 0.238). A confirmed non-MRSA infection within 48 h of ICU admission was associated with increased risk of MRSA acquisition (adjusted odds ratio 2.57, P = 0.005), and receipt of antimicrobial therapy within 48 h of ICU admission was associated with reduced risk of MRSA acquisition (adjusted odds ratio 0.38, P = 0.014). MRSA acquisition does not contribute towards mortality in critically ill patients. This raises questions regarding the cost-effectiveness of focusing infection prevention measures on the control of MRSA in ICUs. The low acquisition rate and lack of risk factors identified for MRSA in the study cohort indicate that efforts should be directed towards continual improvement of standard infection control procedures for all patients.