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

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.

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.

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.

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