Temporal evolution of bacterial species and their antimicrobial resistance characteristics in wound infections of war-related injuries in Ukraine from 2014 to 2023.

BACKGROUND: This study continues surveillance of antimicrobial resistance associated with combat injuries in Ukraine. AIM: To compare species composition, antibiotic resistance profiles, and emergence of new resistance genes between 2014-2020 and 2022-2023. METHODS: Retrospective multicentre microbiological survey in Ukrainian hospitals. Antibiotic susceptibility, whole genome sequencing, and MLST typing were conducted on 154 organisms obtained from 125 casualties from 2022-2023. FINDINGS: The data reveals a predominance of gram-negative bacteria, particularly Acinetobacter baumannii (35.7%), Pseudomonas aeruginosa (14.9%), and Klebsiella pneumoniae (20.7%). High levels of carbapenem resistance was observed among A. baumannii (meropenem 72,2% [(39/54) 95% CI 58.4-83.5], imipenem 66.7% [(36/54) 95% CI 52.5-78.9]), Klebsiella (meropenem 90.6% [(29/32) 95% CI 75.0-98.0], imipenem 81.2% [(26/32) 95% CI 63.6-92.8]), and P. aeruginosa (meropenem 47.8% [(11/23) 95% CI 26.8-69.4], imipenem 60.8% [(14/23) 95% CI 38.5-80.3]) strains. A. baumannii ST-78 and ST-400 were prevalent from 2014 to 2020, while 5 strains of ST-1077 were newly identified. Pseudomonas aeruginosa strains showed diversity across 16 sequence types (STs), with ST-773 increasing in frequency and new STs emerging, but lacking carbapenemase genes. K. pneumoniae exhibited increased genetic diversity over time, with three STs from 2014 to 2020 and six new STs, including blaNDM-1, blaOXA-48, and blaKPC2 carriers, in recent years. CONCLUSION: There is a growing prevalence of multidrug resistant isolates from globally distributed sequence types.

Comparison of Pseudomonas aeruginosa strains reveals that Exolysin A toxin plays an additive role in virulence.

BACKGROUND: Pseudomonas aeruginosa possesses an array of virulence genes ensuring successful infection development. A two-partner secretion system Exolysin BA (ExlBA) is expressed in the PA7-like genetic outliers consisting of ExlA, a pore-forming toxin and ExlB transporter protein. Presence of exlBA in multidrug-resistant (MDR) strains has not been investigated, particularly in the strains isolated from wounded soldiers. METHODS: We screened whole genome sequences of 2439 MDR- P. aeruginosa strains for the presence of exlBA. We compiled all exlBA positive strains and compared them with a diversity set for demographics, antimicrobial profiles and phenotypic characteristics: surface motility, biofilm formation, pyocyanin production and hemolysis. We compared the virulence of strains with comparable phenotypic characteristics in Galleria mellonella. RESULTS: We identified 33 exlBA-positive strains (1.5%). These strains have increased antibiotic resistance, they are more motile, produce more robust biofilms and have comparable pyocianin production with the diversity set despite the phenotypic differences within the group. In in vivo infection models, these strains were less virulent than Type III Secretion System (T3SS) positive counterparts. CONCLUSIONS: exlBA-positive strains are wide spread among the PA7-like outliers. While not as virulent as strains possessing T3SS, these strains exhibit phenotypic features associated with virulence and are still lethal in vivo.