846. Trends in Acinetobacter baumanii Antibiotic Resistance Rates

BACKGROUND: Carbapenem-resistant Acinetobacter baumannii is described as an urgent threat by the Centers for Disease Control and Prevention and several older studies have indicated increasing resistance in Acinetobacter. We sought to describe these trends in the national Veterans Affairs (VA) Healthcare System. METHODS: We assessed A. baumannii positive clinical cultures collected from VA patients (> 18 years) from 2010 to 2018. We categorized cultures based on location at the time of collection: VA medical center (VAMC), community living center (CLC), or outpatient (Outpt). Multidrug resistance (MDR) and extensive drug resistance (XDR) were defined as resistance to > 1 drug in > 3 or all of the following categories, respectively: extended-spectrum cephalosporins (es-CS), fluoroquinolones (FQ), aminoglycosides (AMG), carbapenems (CARB), piperacillin/tazobactam (PIP/TAZ), and ampicillin/sulbactam (AMP/SUL). Joinpoint Software was used for regression analyses of trends over time and to estimate annual average percent changes (AAPC) with 95% confidence intervals. RESULTS: We identified 19,376 A. baumannii positive cultures over the study period (53% VAMCs, 4% CLCs, 43% Outpts), which represented 0.5% of all positive cultures in the VA. In VAMCs, the number of A. baumannii cultures decreased significantly by 12.5% per year. Of all positive cultures in VAMCs, the proportion that were A. baumannii decreased significantly by 5.4% per year. Similar trends were observed in CLCs, while Outpt cultures remained stable. Over the 9-year study period, resistance decreased significantly, with MDR decreasing by 10.2% per year and XDR decreasing by 9.4%. Carbapenem resistance decreased significantly by 4.9% per year in VAMCs (2010, 39%; 2018 28%) and 11.3% in Outpts (2010, 12%; 2018, 6%). Similar annual significant decreases were observed with AMG (9.4%), es-CS (1.4%), and FQ (7.4%) in VAMCs; es-CS (2.7%) and FQ (5.6%) in CLCs; and AMG (9.5%) and FQ (8.2%) in Outpts. CONCLUSION: In the national VA Healthcare System, the prevalence of A. baumannii is decreasing, as is the resistance previously observed with this organism. MDR A. baumannii still made up one-third of cultures in VAMCs and CLCs in 2018, and thus remains a treatment challenge. 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)