Risk factors for isolation of low-level mupirocin-resistant versus -susceptible methicillin-resistant Staphylococcus aureus from patients in intensive care units

SummaryObjectivesThe aim of this study was to determine the risk factors for the recovery of low-level mupirocin-resistant (mupr) or -susceptible (mups) MRSA from patients in intensive care units (ICUs).MethodsA case–case–control study was conducted from November 2003 to April 2004. Two case groups consisted of patients with low-level mupr MRSA and mups MRSA. A control group was frequency matched.ResultsMupr MRSA and mups MRSA were isolated from 20 to 51 patients, respectively, during a six-month period. Risk factors identified for mupr MRSA were as follows: exposure to piperacillin–tazobactam (odds ratio [OR] 13.8; 95% confidence intervals [CI], 1.8–105.0), third-generation cephalosporins (OR, 5.0; 95% CI, 1.6–15.5) and quinolones (OR, 3.4; 95% CI, 1.1–10.7). Risk factors identified for mups MRSA were as follows: length of ICU stay (OR, 1.1; 95% CI, 1.0–1.1), surgery (OR, 3.7; 95% CI, 1.5–9.0), exposure to third-generation cephalosporins (OR, 8.4; 95% CI, 3.3–21.7) and quinolones (OR, 7.7; 95% CI, 2.8–21.3).ConclusionsOur results suggest that nosocomial isolation of low-level mupr MRSA may be affected by piperacillin–tazobactam.