847. Trends in Stenotrophomonas maltophilia Antibiotic Resistance Rates

BACKGROUND: Studies from the 1990’s and 2000’s identified increasing rates of Stenotrophomonas maltophilia, particularly among respiratory isolates and in intensive care populations. Additionally, resistance in S. maltophilia was found to be worsening. We aimed to quantify recent trends in prevalence and resistance of S. maltophilia in the national Veterans Affairs (VA) Healthcare system. METHODS: We identified positive S. maltophilia clinical cultures among VA adult patients from 2010 to 2018, collected in either VA medical centers (VAMCs), community living centers (CLCs), or the outpatient (Outpt) setting. Multidrug resistance (MDR) was defined as resistance to sulfamethoxazole/trimethoprim (SMX/TMP) and minocycline or levofloxacin. Time trends were assessed with regression analyses to estimate annual average percent changes (AAPC) with 95% confidence intervals using Joinpoint Software. RESULTS: Over the 9-year study period, we identified 18,285 S. maltophilia cultures (57% VAMCs, 3% CLCs, 40% Outpt). S. maltophilia cultures made up 0.4% of all positive cultures in the VA. In VAMCs and CLCs, the number of S. maltophilia cultures decreased 5.1% and 8.5% per year, respectively. Alternatively, of all positive cultures in VAMCs, the proportion that were S. maltophilia increased significantly by 2.6% per year. SMX/TMP resistance decreased significantly by 8.5% (2010, 15%; 2018, 6%) per year in VAMCs, and decreased non-significantly by 8.7% (2010, 13%, 2018, 6%) per year in CLCs and 6.0% (2010, 12%; 2018, 7%) in the outpatient setting. No other significant changes in resistance were observed over the study period. MDR increased non-significantly by 1.2% per year. CONCLUSION: While previous studies found increasing rates of S. maltophilia, the number of positive S. maltophilia cultures decreased in the national VA Healthcare System between 2010 and 2018. However, S. maltophilia is making up a greater proportion of positive culture over time. During the study period, resistance to SMX/TMP decreased and now more closely reflects previously reported resistance rates worldwide (0-10%). DISCLOSURES: Aisling Caffrey, PhD, Merck (Research Grant or Support)Pfizer (Research Grant or Support)Shionogi (Research Grant or Support) Haley J. Appaneal, Pharm.D, Shionogi, Inc. (Research Grant or Support) Kerry LaPlante, PharmD, Merck (Advisor or Review Panel member, Research Grant or Support)Ocean Spray Cranberries, Inc. (Research Grant or Support)Pfizer Pharmaceuticals (Research Grant or Support)Shionogi, Inc. (Research Grant or Support)