title: Risk factors associated with mupirocin resistance in meticillin-resistant Staphylococcus aureus.
abstract: Implementation of meticillin-resistant Staphylococcus aureus (MRSA) decolonisation programmes has been increasing and the emergence of mupirocin resistance has been reported. However, the patient-level risk factors associated with mupirocin resistance are not clear. In this study, independent predictors of mupirocin resistance in MRSA among Providence Veterans Affairs Medical Center patients with MRSA-positive culture dates between 1 July 2004 and 30 June 2008 were identified using a frequency-matched case-control study. Forty cases (mupirocin-resistant) were matched on culture date quarter and year to 270 controls (mupirocin-susceptible). The adjusted conditional logistic regression model identified three significant independent predictors associated with mupirocin resistance in MRSA: (1) exposure to mupirocin in the year prior to the culture date [odds ratio (OR): 9.84; 95% confidence interval (CI): 2.93-33.09]; (2) Pseudomonas aeruginosa infection in the year before the culture-related admission (4.85; 1.20-19.61); and (3) cefepime use in the year prior to culture (2.80; 1.03-7.58). In sensitivity analyses, previous mupirocin exposure was associated with low-level [minimum inhibitory concentration (MIC) 8-128mg/L; 23 cases, 202 controls; OR: 6.32; 95% CI: 1.58-25.33] and high-level (MIC ≥256mg/L; 17 cases, 151 controls; OR: 11.18; 95% CI: 1.89-66.30) mupirocin resistance. To our knowledge, this is the first case-control study to reveal a strong association between previous mupirocin exposure and subsequent mupirocin resistance in MRSA, with demonstrated robustness in low- and high-level mupirocin resistance. Mupirocin susceptibility monitoring is critical for facilities instituting decolonisation with mupirocin as increased use may reduce effectiveness through resistance.
authors.affiliation: Veterans Affairs Medical Center, Infectious Diseases Research Program, Providence, Rhode Island, USA.
authors.forename: A R
authors.initials: AR
authors.lastname: Caffrey
authors.forename: B J
authors.initials: BJ
authors.lastname: Quilliam
authors.forename: K L
authors.initials: KL
authors.lastname: LaPlante
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D016022:Case-Control Studies; D024881:Drug Resistance, Bacterial; D005260:Female; D006787:Hospitals, Veterans; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D016712:Mupirocin / Q000494:pharmacology* / Q000627:therapeutic use; D012237:Rhode Island; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D016712:Mupirocin