Prevalence and Clinical Characteristics of Mupirocin-Resistant Staphylococcus aureus

Background: Nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) is a known risk factor for nosocomialtransmission and infection. In an effort to mitigate this problem, topical mupirocin has been widely used for clearing nasal carriage of MRSA. However, mupirocin resistance has become a worldwide concern due to increased use of the antibiotic. The aims of this study were to evaluate the clinical characteristics and prevalence of mupirocin resistance among clinical isolates of staphylococci and to investigate antimicrobial susceptibility. Methods: A total of 175 S. aureus specimens recovered over a 4-month period from various body sites were tested for resistance to mupirocin and other antibiotics using the Vitek2 automated system. The presence of the mupA gene was assessed in isolates exhibiting resistance to mupirocin and in other selected organisms. The clinical characteristics of the isolates were also reviewed. Results: Of the 175 S. aureus isolates, 9.1% (16/175) were resistant to mupirocin, with 1.7% (3/175) having high-level resistance (HR) and 7.4% (13/175) having low-level resistance (LR). Patients with HR-mupirocinresistant S. aureus had a longer duration of hospitalization (P=0.026). Of the 13 LR-mupirocin-resistant S. aureus strains, 11 had identical antibiogram patterns. The mupA gene was detected only among HR isolates. Conclusion: The rate of mupirocin resistance in the S. aureus isolates was high. The spread of mupirocinresistant S. aureus may be due to nosocomial infection. (Korean J Clin Microbiol 2011;14:18-23)