279Prevalence and Epidemiology of Mupirocin Resistance Among Those Colonized with Methicillin-resistant Staphylococcus aureus in the Community

Background. Mupirocin ointment is often used to attempt eradication of colonization with methicillin-resistant Staphylococcus aureus (MRSA). However, mupirocin resistance, particularly among community-onset MRSA strains, has been increasing. This study sought to describe the prevalence and epidemiology of mupirocin resistance among community-dwelling subjects and their colonized household members. Methods. Over a three year time period, surveillance cultures for MRSA colonization were obtained from patients presenting to an ambulatory setting with an acute MRSA skin and soft tissue infection (i.e., index case) and their household members. All MRSA isolates obtained from subjects were evaluated for mupirocin minimum inhibitory concentration (MIC) using Etest1 . Isolates with high-level mupirocin resistance (MIC >512 μg/ml) were compared to susceptible isolates on the basis of SCCmec type, spa typing and susceptibilities to other commonly tested antimicrobials. Results. Four hundred thirty-four isolates were included in the analysis. Nineteen (4.4%) isolates demonstrated high-level mupirocin resistance (HLMR). Approximately half of these (47.4%) were isolated from index cases. The results are demonstrated in the table. Clindamycin resistance was seen more commonly among isolates with HLMR(42.1% vs 9.2%; P < 0.001). No isolates demonstrated resistance to trimethoprim-sulfamethoxazole. No differences were seen by SCCmec type. The predominant spa type seen in both susceptible and HLMR isolates was t008. However, this was more commonly seen in susceptible isolates.