Abstract Background Nasal decolonization with mupirocin has been noted in professional society guidance since 2014 as an optional measure to prevent methicillin-resistant Staphylococcus aureus (MRSA) infection in certain high-risk settings or patients (i.e., intensive care unit ICU or undergoing high-risk surgery). Because of concerns about emergence of resistance, we evaluated trends in mupirocin resistance among MRSA isolates from invasive infections and associations between healthcare exposures and resistance.Figure 1.Percentage of methicillin-resistant Staphylococcus aureus isolates from invasive infections with high-level and low-level mupirocin resistance by year, CDC Emerging Infections Program surveillance, 2005-2022 Methods Isolates from the Emerging Infections Program active, population-based surveillance for invasive MRSA were submitted to CDC from a convenience sample of cases during 2005-2022. A case was MRSA isolated from a normally sterile body site in a surveillance area resident. Isolates were tested using reference broth microdilution and were considered mupirocin susceptible if the minimum inhibitory concentration (MIC) was ≤ 4µg/mL, low-level resistant (LLR) if MIC ≥ 8µg/mL and ≤ 256µg/mL, or high-level resistant (HLR) if MIC 256µg/mL. Annual proportions of LLR and HLR isolates were calculated. Trends were assessed using the Cochran-Armitage test. For 2019-2022 isolates, healthcare exposures of cases with HLR vs. susceptible isolates were compared. Results During 2005-2022, CDC tested 11,451 MRSA isolates for mupirocin resistance, representing 28.5% of total MRSA cases. Annual HLR isolates ranged from 0 – 6.1% (Figure). During 2005-2013, HLR isolates increased from 1% to 5.4% (P .001); during 2014-2022, HLR isolates ranged between 2.6%-6.1% with no significant trend (P=0.55). Cases with HLR (n=68) vs. susceptible (n=1,648) isolates during 2019-2022 did not have significantly different healthcare exposures, including: surgery ≤ 90 days (P=0.55) or ≤ 1 year prior (P=0.15), hospitalization ≤ 1 year prior (P=0.91), ICU care or presence of a central line ≥ 2 days prior (P=0.43 and P=0.53, respectively), or chronic hemodialysis (P=0.34). Conclusion Mupirocin resistance among invasive MRSA isolates did not increase significantly after the 2014 guidance and was not associated with selected healthcare exposures. Continued monitoring is needed to assess possible changes in mupirocin resistance as practices and additional strategies for nasal decolonization are evaluated. Disclosures William Schaffner, MD, Abbott Dignostics: Honoraria
Kulb et al. (2026) studied this question.