Antimicrobial activity of sulbactam-durlobactam against Acinetobacter baumannii-calcoaceticus complex strains causing non-respiratory and non-bloodstream infections from the United States (2023–2025)

Acinetobacter baumannii most often causes pneumonia in critically ill patients. However, A. baumannii is also an important cause of a broader range of infections, including skin/wound and urinary tract infections. This study aims to evaluate the in vitro activity of sulbactam-durlobactam and comparator antibiotics, including meropenem and cefiderocol against A. baumannii-calcoaceticus complex isolates from non-respiratory and non-bloodstream sources. Samples included 285 A. baumannii-calcoaceticus complex isolates enriched for carbapenem resistance collected across 17 states in the United States (January 2023–May 2025). Antimicrobial susceptibility tests were conducted by manual broth microdilution and interpreted according to Clinical and Laboratory Standards Institute (CLSI) and Food and Drug Administration (FDA) (cefiderocol) standards. A. baumannii complex isolates were primarily cultured from skin/wound (58.6%), urinary tract (31.6%), and other sources (9.8%), including cerebrospinal and peritoneal fluid. Carbapenem resistance was observed in approximately 70% of isolates and more common among skin/wound cultures. Sulbactam-durlobactam was observed to be highly active (96.9% susceptible [S]; MIC₉₀ 4 mg/L) and demonstrated greater activity than sulbactam (37.9% S; MIC₉₀ 32 mg/L). Sulbactam-durlobactam also displayed high susceptibility rates across isolate sources, ranging from 96.4 (skin/wound) to 97.8% (urine). Cefiderocol demonstrated similar in vitro activity across culture sources and patient location, inhibiting >90 and >80% of isolates at CLSI and FDA susceptible breakpoints, respectively. Minocycline susceptibility was 69.1%, while tigecycline and eravacycline MICs_50/90 were 1/4 and 0.5/1 mg/L, respectively. The observed data are consistent with results from surveillance studies among respiratory and bloodstream isolates and show that sulbactam-durlobactam demonstrates potent in vitro activity against clinical A. baumannii complex isolates from a variety of culture sources.