1232. Mupirocin Susceptibility of Staphylococcus aureus (SA), 2022: Is It Time for Change in MRSA Decolonization?

Abstract

Abstract Background Nasal decolonization with mupirocin has been a commonly used strategy for the prevention of surgical site infections (SSIs) due to SA. We recently noted an increase in SSIs due to SA despite the use of mupirocin, including a case of post-operative mupirocin-resistant MRSA infection despite intranasal mupirocin. We therefore evaluated the mupirocin susceptibility of SA at Stamford Hospital to determine the optimal regimen for decolonization. Methods SA isolates were recovered from clinical and screening samples received in the microbiology laboratory from 8/1/2020 to 2/28/2022. Mupirocin susceptibility was determined using e-tests and a standardized inoculum on Mueller-Hinton agar. Isolates were categorized as “susceptible” (MuS) with minimum inhibitory concentrations (MIC) ≤4 mcg/ml or resistant (MuR) with MIC values ≥8mcg/ml. Resistant strains were further divided into low-level resistance, with MIC values from 8 to 256 mcg/ml, and high-level resistance, with MIC values >256/ml. SA isolates were identified and tested for susceptibility by usual Clinical Laboratory Standards Institute (CLSI) criteria. Results 223 unique SA isolates from 218 patients were tested. Patients ranged in age from newborn to 94 years. Twenty-four SA isolates (10.8%) were resistant to mupirocin (20 MRSA and 4 MSSA). Of the 24 MuR strains, 19 (79.2%) isolates demonstrated high-level resistance. MRSA strains were more likely to be resistant (22.5% were MuR) than MSSA strains (3.0% were MuR) (p< 0.001). MuR strains did not differ from MuS strains with respect to patient age, sex, race, site of isolation, infected versus colonized, community-acquired versus hospital-acquired or inpatient/out-patient location. Conclusion Preventing surgical site infections is challenging. Decolonization with mupirocin nasal ointment has been a common component of preoperative optimization. However, the emergence of resistance would render mupirocin suboptimal and other regimens might be preferred. In our study, less than 80% of MRSA strains were MuS. These findings are concerning and have led us to reevaluate our current decolonization strategy. In patients colonized with MRSA at high risk for infection (e.g. total joint replacement), intranasal povidone iodine may be preferable to mupirocin. Disclosures All Authors: No reported disclosures.