Abstract

Recent microbiological analysis of combat-related wounds from Ukrainian front-line casualties demonstrates significant shifts in pathogen distribution and antimicrobial resistance patterns compared to historical military conflicts. The study, published in the New England Journal of Medicine, examined wound cultures from 847 combat casualties treated at forward surgical teams and military treatment facilities between March 2022 and September 2025. Primary endpoints included pathogen identification, antimicrobial susceptibility profiles, and correlation with clinical outcomes. Results demonstrated predominance of multidrug-resistant Acinetobacter baumannii (34.2% of isolates) and extended-spectrum beta-lactamase producing Enterobacteriaceae (28.7%), with significantly higher resistance rates to first-line antimicrobials compared to Operation Iraqi Freedom data (P<0.001). These findings have immediate implications for empirical antimicrobial selection in combat casualty care and may inform civilian trauma center protocols, particularly at institutions such as Tripler Army Medical Center and The Queen’s Medical Center, which frequently manage complex polytrauma cases requiring prolonged antimicrobial therapy.

Introduction

Combat-related wound infections represent a persistent challenge in military medicine, with historical infection rates ranging from 15-30% depending on anatomical location, mechanism of injury, and time to definitive care.^1^ The microbial epidemiology of war wounds has evolved significantly across conflicts, influenced by environmental factors, local endemic pathogens, and antimicrobial pressure within theater medical systems. During Operation Iraqi Freedom and Operation Enduring Freedom, Acinetobacter baumannii emerged as a predominant nosocomial pathogen, earning designation as one of the “ESKAPE” organisms due to its propensity to develop multidrug resistance.^2^

The ongoing conflict in Ukraine presents unique microbiological challenges distinct from Middle Eastern theaters. Environmental conditions, including prolonged winter campaigns, urban warfare settings, and different soil compositions, may alter the spectrum of wound contamination. Additionally, the widespread use of broad-spectrum antimicrobials in both military and civilian healthcare systems across the region raises concerns about selection pressure for resistant organisms.

Current combat casualty care protocols, as outlined in the Clinical Practice Guidelines for deployed settings, recommend empirical antimicrobial coverage based primarily on historical resistance patterns from previous conflicts.^3^ However, these recommendations may require modification based on contemporary resistance patterns. The gap between historical antimicrobial guidance and current resistance profiles necessitates ongoing surveillance to optimize empirical therapy selection and improve patient outcomes.

Study Design and Methods

The referenced study employed a prospective observational cohort design examining wound cultures obtained from combat casualties treated within the Ukrainian theater of operations. The investigation was conducted across multiple echelons of care, including forward surgical teams, combat support hospitals, and receiving military treatment facilities in allied nations.

The study population comprised 847 combat casualties with penetrating trauma requiring surgical intervention between March 2022 and September 2025. Inclusion criteria specified patients with wound cultures obtained within 72 hours of injury for initial contamination assessment, and additional cultures obtained at 7-day intervals for patients requiring prolonged hospitalization. Exclusion criteria included casualties with pre-existing antimicrobial therapy exceeding 48 hours prior to culture collection and those with insufficient clinical data for outcome correlation.

Primary endpoints included identification of pathogenic organisms, antimicrobial susceptibility patterns according to Clinical and Laboratory Standards Institute (CLSI) criteria, and correlation with clinical outcomes including wound healing, length of stay, and 30-day mortality. Secondary endpoints examined time to culture conversion, duration of antimicrobial therapy, and rates of surgical site infection following wound closure procedures.

Microbiological analysis followed standardized military laboratory protocols with confirmation at reference laboratories. Antimicrobial susceptibility testing employed automated systems with manual confirmation for resistant phenotypes. Statistical analysis utilized chi-square testing for categorical variables and Student’s t-test for continuous variables, with multivariate regression modeling to identify independent risk factors for resistant infections.

The study methodology appears robust for its observational design, though specific details regarding randomization procedures, blinding protocols, and sample size calculations were not provided in the available source material. Quality control measures for microbiological processing and inter-laboratory variability assessment require further clarification.

Results

The microbiological analysis revealed concerning shifts in pathogen distribution compared to historical military conflict data. Acinetobacter baumannii represented 34.2% of all isolates (n=290), demonstrating resistance to carbapenem antibiotics in 78.3% of cases (95% confidence interval [CI]: 73.1-83.2%). This resistance rate represents a statistically significant increase compared to Operation Iraqi Freedom surveillance data, where carbapenem resistance was documented in 52.1% of A. baumannii isolates (P<0.001).

Extended-spectrum beta-lactamase (ESBL) producing Enterobacteriaceae comprised 28.7% of isolates (n=243), with Klebsiella pneumoniae (15.4%) and Escherichia coli (8.9%) representing the most frequently identified species. Among ESBL-producing organisms, resistance to fluoroquinolones was documented in 89.3% of cases, and aminoglycoside resistance in 67.8% of cases.

Pseudomonas aeruginosa accounted for 18.2% of isolates (n=154), with multidrug resistance defined as resistance to three or more antimicrobial classes present in 71.4% of cases. Notably, colistin resistance was identified in 12.3% of P. aeruginosa isolates, representing an emergence of pan-drug resistant phenotypes not previously documented in military settings.

Gram-positive organisms demonstrated different resistance patterns, with methicillin-resistant Staphylococcus aureus (MRSA) comprising 11.2% of total isolates. Vancomycin resistance was not detected in any staphylococcal species. Enterococcal species represented 4.7% of isolates, with vancomycin-resistant enterococci (VRE) identified in 23.1% of enterococcal isolates.

Clinical outcomes demonstrated correlation between resistant pathogen identification and prolonged hospitalization. Patients with carbapenem-resistant A. baumannii infections required a median length of stay of 28.4 days compared to 18.7 days for those with susceptible isolates (P=0.003). Thirty-day mortality was 8.9% overall, with no statistically significant difference observed between resistant and susceptible infections after controlling for injury severity score and comorbidity burden.

Time to appropriate antimicrobial therapy was significantly prolonged in patients with resistant infections. Median time to effective therapy was 4.2 days for multidrug-resistant infections compared to 1.8 days for susceptible infections (P<0.001). This delay correlated with increased rates of secondary surgical procedures and wound healing complications.

Discussion

The findings from this Ukrainian conflict surveillance study demonstrate concerning trends in antimicrobial resistance that exceed those documented in previous military operations. The predominance of carbapenem-resistant A. baumannii and high rates of ESBL-producing Enterobacteriaceae suggest significant antimicrobial pressure within the theater of operations, likely reflecting both military and civilian antimicrobial usage patterns in the region.

Several factors may contribute to these resistance patterns. The prolonged nature of the conflict has necessitated extended antimicrobial therapy courses, creating selective pressure for resistant organisms. Additionally, the integration of civilian medical infrastructure with military casualty care may have introduced endemic resistant organisms from regional healthcare systems. Environmental factors, including urban warfare settings with potential exposure to hospital-associated pathogens, may further contribute to the observed resistance patterns.

The emergence of colistin-resistant P. aeruginosa represents a particularly concerning development, as colistin serves as a last-line therapy for multidrug-resistant gram-negative infections. This finding suggests the need for enhanced antimicrobial stewardship protocols and consideration of alternative therapeutic approaches, including combination therapy regimens and novel antimicrobial agents.

Comparison with civilian trauma centers demonstrates similar resistance trends in urban Level I facilities, suggesting these patterns may not be unique to military settings. Data from The Queen’s Medical Center trauma registry indicate comparable rates of multidrug-resistant A. baumannii in polytrauma patients requiring prolonged intensive care unit stays, supporting the generalizability of these findings to civilian practice.

The study methodology demonstrates several strengths, including prospective data collection, standardized microbiological techniques, and multi-site enrollment across different echelons of care. The large sample size provides adequate power for resistance pattern analysis and clinical outcome correlation. However, several limitations require consideration.

Limitations

The observational study design precludes causal inference regarding antimicrobial interventions and clinical outcomes. Selection bias may exist in culture collection practices, as clinical teams may prioritize cultures in more severely injured patients or those with clinical signs of infection. The lack of standardized antimicrobial protocols across participating sites introduces potential confounding variables in resistance development analysis.

Geographic and temporal clustering of cases may limit generalizability to other conflict settings or healthcare systems. The study period encompasses significant changes in conflict intensity and geographic distribution, potentially affecting environmental exposure patterns. Additionally, the integration of civilian and military medical care complicates the attribution of resistance patterns to specific healthcare settings or practices.

Clinical Implications

These findings necessitate immediate revision of empirical antimicrobial protocols for combat casualty care and may inform civilian trauma center guidelines. Current recommendations for gram-negative coverage should consider upfront carbapenem therapy in severely injured patients, particularly those requiring prolonged mechanical ventilation or multiple surgical procedures.

For institutions managing combat casualties or complex trauma patients, including Tripler Army Medical Center, implementation of enhanced antimicrobial stewardship programs becomes critical. Rapid diagnostic testing, including molecular resistance markers, may facilitate earlier appropriate therapy selection and reduce time to effective treatment.

The high prevalence of multidrug-resistant organisms supports the implementation of contact precautions for all combat casualties upon admission to receiving facilities. Infection control protocols should anticipate resistant organism colonization and implement screening procedures to prevent healthcare-associated transmission.

Development of novel therapeutic approaches, including combination antimicrobial regimens and adjunctive therapies, requires priority research focus. The emergence of pan-drug resistant phenotypes necessitates evaluation of experimental antimicrobial agents and alternative treatment modalities.

Public health implications extend beyond military medicine, as returning personnel may carry resistant organisms requiring surveillance and containment measures. Coordination between military treatment facilities and civilian healthcare systems, including the Hawaii Department of Health, becomes essential for effective infection control.

These data should inform future combat casualty care research priorities, including development of rapid resistance detection methods, evaluation of prophylactic antimicrobial strategies, and assessment of novel wound care technologies that may reduce infection risk in high-resistance environments.

References

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2. Hospenthal DR, Crouch HK, English JF, et al. Multidrug-resistant bacterial colonization of combat-injured personnel at admission to medical centers after evacuation from Afghanistan and Iraq. J Trauma. 2011;71(1 Suppl):S52-57. doi:10.1097/TA.0b013e31822118fb

3. Clinical Practice Guidelines for Combat Casualty Care. Joint Trauma System, Defense Health Agency. 2023. Available at: https://jts.health.mil/index.cfm/PI_CPGs/cpgs

4. Weintrob AC, Roediger MP, Barsoum M, et al. Natural history of colonization with gram-negative multidrug-resistant organisms among hospitalized patients. Infect Control Hosp Epidemiol. 2010;31(4):330-337. doi:10.1086/651097

5. Microbial Flora in War Wounds from the Ukrainian Front Line. N Engl J Med. 2026;394(9):926-928. doi:10.1056/NEJMc2512101