TESTING METAL-BETALACTAMASE INHIBITORS TO DETERMINE MICROORGANISMS SENSITIVITY TO ANTIBACTERIAL DRUGS BY THE DISC-DIFFUSE METHOD

The aim of the study is to evaluate the effect of metallo-β-lactamase inhibitors (MBLIs) on preserving the antimicrobial activity of antibiotics against microorganisms. Objectives: selection, synthesis, and evaluation of complexing agents capable of forming stable complexes with zinc, a metal contained in the active center of MBLIs, and evaluation of their compatibility with antibiotics; determination of the optimal ratio of antibiotic to metallo-β-lactamase inhibitor (MBLI); evaluation of the antimicrobial activity of combinations of an antibiotic with a metallo-β-lactamase inhibitor (MBLI) on a mixed culture of bacterial microorganisms causing diseases of the distal extremities (Staphylococcus spp.) and on a fungal test culture (Candida tropicalis). Data collection and analysis were conducted according to Guideline 4.2.3676-20 "Methods of laboratory research and testing of disinfectants to assess their efficacy and safety" in 2025 in the Veterinary Sanitation Laboratory of the Biotechnology Department of the Federal Center for Toxicology, Radiation, and Biological Safety, as well as in the Mycotoxins Laboratory of the Toxicology Department. Test cultures were obtained from the microorganism collection of the Federal Center for Toxicology and Radiation Safety (FCTRB-VNIVI). The choice of metallo-β-lactamase inhibitor (MBL) components was based on the complexing properties of zinc ions, which are part of the active site of β-lactamases. All test samples with the calculated content of IMBL based on benzylpenicillin, amoxicillin and ceftiofur showed antimicrobial activity against microorganisms (Escherichia coli, Clostridium perfrinens, Streptococcus spp., Staphylococcus spp., Candida tropicalis). The most pronounced antimicrobial and anti-drug resistance activity was observed with ceftiofur and amoxicillin when EDTA, a chelating agent, was added: it increased almost twofold. When using amoxicillin, a pronounced effect was observed when zoledronic acid was used as an IMBLM. However, when using tartrate, the opposite effect was observed. Therefore, tartrate should be excluded from potential IMBLM formulations when using amoxicillin (as well as any antibiotics containing a free phenolic group). High-molecular-weight chelating agents, particularly those like EDTA, exhibit inhibitory effects on mixed microbial cultures, Staphylococcus aureus strains, and even extremely antibiotic-resistant yeasts (Candida tropicalis). The study results will enable the development of new formulations of drugs using IMBLM.