Abstract
BACKGROUND: Acinetobacter baumannii most often causes nosocomial bacteremia and pneumonia. However, A. baumannii is becoming an important cause of a broader range of infections including skin and soft tissue infection (SSTI) and urinary tract infections (UTI). This study aims to evaluate the in vitro activity of sulbactam-durlobactam and other clinically utilized antibiotics against A. baumannii-calcoaceticus complex isolates isolated from non-respiratory and non-bloodstream sources. [Figure: see text] METHODS: Samples included 193 A. baumannii-calcoaceticus complex isolates collected from 2023-2025 across 19 states. Susceptibility tests for sulbactam-durlobactam (durlobactam fixed concentration of 4 mg/L), and comparator agents were conducted by manual broth microdilution and interpreted according to CLSI and FDA (cefiderocol) standards. RESULTS: A. baumannii complex isolates were primarily cultured from skin and soft tissue (56.5%), followed by urinary tract (31.6%) and other sources (11.9%) including bone biopsy, fluid aspirate etc. ICU patients contributed 20% of the isolates. Sulbactam-durlobactam was observed to be highly active (98.5% susceptible [S]; MIC(50/90) 1/4 mg/L), demonstrating greater activity than ampicillin-sulbactam (41.5% S; MIC(50/90) 8/32 mg/L) and meropenem (32.1% S; MIC(50/90) 32/128 mg/L). Sulbactam-durlobactam also displayed high susceptibility rates across sample sources, ranging from 97.3% (skin and soft tissue) to 100% (urine). The MIC(50/90) and susceptibility rates for all other agents including tetracycline derivatives are shown in Table 1. Notably, among the carbapenem-resistant A. baumannii (CRAB) isolates (n=130) in the collection, sulbactam-durlobactam retained high activity (97.7% S) relative to ampicillin-sulbactam (16.2% S). Cefiderocol inhibited 97.7% and 75.4% of isolates at CLSI and FDA susceptible breakpoints, respectively. CONCLUSION: The data reported here are consistent with results from surveillance studies among non-respiratory and bloodstream isolates and show that sulbactam-durlobactam demonstrates in vitro activity against clinical A. baumannii complex isolates from urinary tract and SSTI sources, including isolates that are resistant to ampicillin-sulbactam, carbapenems, and cefiderocol. DISCLOSURES: Tomefa E. Asempa, PharmD, Innoviva: Grant/Research Support Robin R. Chamberland, PhD D(ABMM), bioMerieux: Advisor/Consultant|Pattern Bioscience, Inc.: Advisor/Consultant|Pattern Bioscience, Inc.: Grant/Research Support Jonathan Hand, MD, AstraZeneca: Advisor/Consultant|AstraZeneca: Grant/Research Support|Ferring: Grant/Research Support|Innoviva: Advisor/Consultant|Janssen: Grant/Research Support|Pfizer: Advisor/Consultant|Pfizer: Grant/Research Support|Scynexis: Grant/Research Support|The Antibiotic Resistance Leadership Group (ARLG): Grant/Research Support|The Antibiotic Resistance Leadership Group (ARLG): Honoraria Amanda Harrington, PhD, Beckman Coulter: Grant/Research Support|bioMerieux/BioFire: Advisor/Consultant|bioMerieux/BioFire: Grant/Research Support|bioMerieux/BioFire: Honoraria|BioRad: Advisor/Consultant|Selux: Grant/Research Support Wesley D. Kufel, Pharm.D., BCPS, BCIDP, Merck & Co.: Grant/Research Support|Shionogi, Inc: Grant/Research Support|Shionogi, Inc: Honoraria Lars Westblade, PhD, Elements Materials Technology: Grant/Research Support|Hardy Diagnostics: Grant/Research Support|Melinta Therapeutics: Grant/Research Support|Selux Diagnostics: Grant/Research Support|Shionogi: Advisor/Consultant|SNIPRBIOME: Grant/Research Support Thomas Kirn, MD PhD, BD: Advisor/Consultant|BD: Honoraria Brian Mochon, PhD, D(ABMM), Shionogi: Advisor/Consultant Mark Fisher, PhD, Shionogi Inc.: Advisor/Consultant Rebekah Dumm, PhD D(ABMM), BD: Advisor/Consultant|BD: Grant/Research Support|Biomerieux: Advisor/Consultant|Biomerieux: Grant/Research Support|Diasorin: Grant/Research Support|Pattern Biosciences: Grant/Research Support|Qiagen: Grant/Research Support|Roche Diagnostics: Advisor/Consultant|Shionogi: Advisor/Consultant David P. Nicolau, PharmD, CARB-X: Grant/Research Support|Innoviva: Advisor/Consultant|Innoviva: Grant/Research Support|Shionogi: Advisor/Consultant|Shionogi: Grant/Research Support