oa Southern African Journal of Infectious Diseases - High prevalence of mupirocin resistance associated with resistance to other antimicrobial agents in Staphylococcus aureus isolated from patients in private health care, Western Cape : original research
Staphylococcus aureus is an opportunistic pathogen which results in high morbidity and mortality. Decolonisation of the carriers by the intranasal administration of mupirocin is frequently prescribed in infection control practice. The aim of this study was to establish the prevalence of mupirocin resistance in our setting and to investigate the association between mupirocin resistance and resistance to other antimicrobial agents. We simultaneously evaluated laboratory procedures for the sensitivity testing of mupirocin. Standardised disc sensitivity testing for high-level resistance to mupirocin was performed on a prospective sample of 997 unique clinical isolates of S. aureus. The results were confirmed with molecular testing. We also evaluated the reliability of automated sensitivity testing by Vitek® 2. Statistical methods were used to estimate associations between high-level resistance to mupirocin and resistance to other antimicrobial agents. High-level mupirocin resistance prevalence was 23.37% [95% confidence interval (CI): 20.77-26.12]. The phenotypic results agreed with the molecular tests for the mupA gene. Raw agreement between standardised disc sensitivity and the automated method was 94.38%, with a weighted kappa of 0.8767 (95% CI: 0.83-0.90). We found statistically significant associations between high-level mupirocin resistance and resistance to cloxacillin, fusidic acid, fluoroquinolones, co-trimoxazole and macrolide-lincosamide-streptogramin B phenotypes. The high prevalence of mupirocin resistance in this setting necessitates sensitivity testing before decolonisation with mupirocin. The correlation between high-level mupirocin resistance and resistance to other antimicrobial agents implies selective pressure for more resistant strains, which should be considered in the practice of antimicrobial stewardship.
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