Phenotypic and genotypic analysis of Acinetobacter baumannii isolated from combat wounds in Ukraine during 2022 and 2023

Background Acinetobacter baumannii is an important nosocomial pathogen worldwide. During the current invasion of Ukraine, reports of infections caused by this organism have proliferated. Here, we provide a phenotypic and genotypic analysis of A. baumannii associated with the conflict. Methods Between March 2022 and September 2023, 68 A. baumannii strains were cultured from wounded Ukrainian service members in three hospitals in west-central Ukraine. Antibiotic susceptibility and WGS were performed on all isolates. Results Strains encompassed eight different STs, including the emerging ST78 (and its single locus variant ST1077) and globally distributed ST2 lineages, with ST19 being the most common (25%). Fifty strains carried at least one acquired carbapenemase (bla_OXA-23 or bla_OXA-72), with seven strains carrying both. Overall, susceptibility ranged from 0% (fluoroquinolones) to 100% (SUL/durlobactam) and all strains had CST MICs <1 mg/mL. Notably, all but one ST2 isolates were resistant to FDC, and this correlated with the presence of the bla_PER-1 or bla_PER-7 ESBL genes. In contrast, 8 of 13 ST78 were FDC non-susceptible, but non-susceptibility was correlated with the disruption of the pirA siderophore receptor gene by ISAba35. Finally, passage in MEM of one strain for 8 days resulted in a mutation of the bla_GES-11 ESBL to the bla_GES-14 carbapenemase. Conclusions Sampling of A. baumannii strains infecting injured Ukrainian soldiers revealed the predominance of known (ST2) and emerging (ST19, ST78) lineages carrying carbapenemases. Antibiotic resistance was broad, including the recently approved catechol-substituted siderophore cephalosporin, FDC, highlighting the immense treatment challenges faced by medical personnel during this ongoing conflict.