Pandrug-resistant Klebsiella pneumoniae isolated from Ukrainian war victims are hypervirulent

The price of WAR: AMR

Background

The ongoing conflict in Ukraine has exacerbated the risk of MDR bacterial infections in war-injured patients.

Methods

We present the case of a Ukrainian soldier who sustained a traumatic explosive injury to the bilateral lower extremities, underwent surgery and subsequently experienced an infection with a carbapenem-resistant Klebsiella pneumoniae. The isolate was subject to genomic WGS.

Results

This case study describes the successful management of a traumatic injury in a Ukrainian soldier infected with a carbapenem-resistant K. pneumoniae isolated from surgical wounds. WGS revealed a hypervirulent ST147 strain carrying multiple resistance and virulence factors, including bla NDM-1. Treatment with ceftazidime/avibactam and aztreonam was effective.

Conclusions

Ceftazidime/avibactam and aztreonam is highlighted as a promising regimen for MDR infections in conflict zones.

Management and Prevention of Multidrug-Resistant Bacteria in War Casualties

The growing threat of antimicrobial resistance (AMR) is a critical issue for both civilians and the military. With each successive conflict, pathogens become more resistant, making the management of infections in casualties increasingly challenging. To better understand the scope and characteristics of conflict-related AMR, a comprehensive literature search was conducted in the PubMed database in April 2025, using defined search terms related to war casualties and antimicrobial resistance. We screened and included 117 relevant publications, comprising original research articles, reviews, case series, case reports, editorials, and commentaries, published in English or French, with no date restriction. This narrative review synthesizes current evidence on multidrug-resistant bacteria most commonly isolated from war casualties, their associated resistance mechanisms, and the microbiological diagnostic tools available at various levels of the military continuum of care (Roles 1-4). It also presents strategies for preventing cross-contamination and infection in resource-limited combat settings and provides practical, field-adapted recommendations for clinicians, from first responders to specialized care providers, aiming to improve infection management in armed conflict zones and mitigate the spread of AMR.

In Vitro Elimination of Highly Multidrug-Resistant Bacteria by the Lactic Acid Bacterial Drug Candidate ILP100

INTRODUCTION

Multidrug resistance (MDR) has been identified in wound bacterial isolates from Ukrainian war victims treated in Ukraine and across Europe. ILP100, a drug candidate for the treatment of skin wounds, is composed of a Limosilactobacillus reuteri expressing human chemokine CXCL12. In this study, the antimicrobial effects of ILP100 were tested on MDR bacteria isolated from wounds of Ukrainian war victims.

METHODS

ILP100 was co-cultured with one of the wound pathogens (Pseudomonas aeruginosa, Acinetobacter baumannii, Enterobacter cloacae, Klebsiella pneumoniae, Proteus mirabilis, Staphylococcus aureus; 12 non-MDR and 12 MDR isolates) in broth media for 12 h with subsequent survival recovery on agar plates. Additionally, agar plates were precoated with ILP100 at clinical doses (3 vs. 24 h, 1 × 107 CFU/cm2) followed by co-culture with pathogens inoculated in soft agar (1 × 104 CFU/cm2). To compare ILP100 with relevant antibiotics, MDR-inoculated soft agar was applied to plates with standardized ILP100 drops and antibiotic-loaded discs, followed by 18-20 h aerobic incubation at 37 °C.

RESULTS

Dose-dependent growth inhibition of all pathogens was demonstrated, as 1000:1 and 100:1 (ILP100/isolate) inhibited pathogenic growth up to log 6.4 and log 4.3 CFU/ml, respectively. Potent antimicrobial effects were demonstrated after precoating with ILP100, as pathogen recovery was only demonstrated after 3 h of precoating, only for 10/18 isolates and then only partially. Benchmarking to relevant antibiotic discs resulted in large cleared zones surrounding the ILP100 spots but not the antibiotic discs, demonstrating potent bacterial killing by ILP100-secreted factors. Interestingly, the MDR pathogens were significantly more sensitive to the ILP100 released factors than the non-MDR isolates.

CONCLUSION

ILP100 effectively eliminates MDR wound pathogens, which reveals a promising strategy for the development of new classes of urgently needed antimicrobials.

Acinetobacter baumannii Clinical Isolates Resist Complement-Mediated Lysis by Inhibiting the Complement Cascade and Improperly Depositing MAC

INTRODUCTION

Acinetobacter baumannii is a gram-negative opportunistic bacterium that causes life-threatening infections in immunocompromised hosts. The complement system is a critical mechanism of innate immunity that protects the human body from bacterial infections. Complement activation leads to the deposition of the membrane attack complex (MAC), which can directly lyse gram-negative bacteria. However, A. baumannii has developed evasion mechanisms to protect itself from complement.

METHODS

Complement deposition was investigated by flow cytometry and Western blotting. Soluble MAC formation was assessed by ELISA. Bacterial serum resistance was determined by the SYTOX Green Assay. Galleria mellonella was used as an infection model. Genome sequencing revealed virulence genes carried by isolates.

RESULTS

We examined clinical isolates of A. baumannii and found 11 isolates with MAC deposition and 5 isolates without deposition. Trypsinization of MAC-positive isolates significantly reduced MAC, indicating incorrect insertion, consistent with a lack of lysis of these strains. MAC-negative isolates inhibited alternative pathway activation and were significantly more serum-resistant. These strains were also more virulent in a G. mellonella infection model. Whole genome sequencing revealed that MAC-negative isolates carried more virulence genes, and both MAC-negative and MAC-positive A. baumannii significantly differed in capsule type. Importantly, a correlation was observed between complement inhibition and capsule type (e.g., capsule locus KL171) of MAC-negative bacteria, while the capsule type (e.g., KL230) of MAC-positive A. baumannii was associated with increased sensitivity to MAC-mediated lysis.

CONCLUSION

Our findings suggest a relationship between capsule type, complement resistance, and host virulence in A. baumannii.

INTRODUCTION

Acinetobacter baumannii is a gram-negative opportunistic bacterium that causes life-threatening infections in immunocompromised hosts. The complement system is a critical mechanism of innate immunity that protects the human body from bacterial infections. Complement activation leads to the deposition of the membrane attack complex (MAC), which can directly lyse gram-negative bacteria. However, A. baumannii has developed evasion mechanisms to protect itself from complement.

METHODS

Complement deposition was investigated by flow cytometry and Western blotting. Soluble MAC formation was assessed by ELISA. Bacterial serum resistance was determined by the SYTOX Green Assay. Galleria mellonella was used as an infection model. Genome sequencing revealed virulence genes carried by isolates.

RESULTS

We examined clinical isolates of A. baumannii and found 11 isolates with MAC deposition and 5 isolates without deposition. Trypsinization of MAC-positive isolates significantly reduced MAC, indicating incorrect insertion, consistent with a lack of lysis of these strains. MAC-negative isolates inhibited alternative pathway activation and were significantly more serum-resistant. These strains were also more virulent in a G. mellonella infection model. Whole genome sequencing revealed that MAC-negative isolates carried more virulence genes, and both MAC-negative and MAC-positive A. baumannii significantly differed in capsule type. Importantly, a correlation was observed between complement inhibition and capsule type (e.g., capsule locus KL171) of MAC-negative bacteria, while the capsule type (e.g., KL230) of MAC-positive A. baumannii was associated with increased sensitivity to MAC-mediated lysis.

CONCLUSION

Our findings suggest a relationship between capsule type, complement resistance, and host virulence in A. baumannii.