Аннотация:A quantitative assessment of the antibacterial effect of silver nanoparticles on polyantibiotic-resistant gram-positive and gram-negative microorganisms was carried out. Silver nanoparticles synthesized by environmentally friendly metal-steam synthesis method. The size and electronic state of nanoparticles were investigated by transmission electron and X-ray photoelectron spectroscopy. The assessment of the antibacterial properties of nanomaterials was carried out on two clinical pathogenic strains of gram-positive and four strains of gram-negative microorganisms. The typing and assessment of bacterial resistance to antibiotics was carried out on a microbiological analyzer. The quantitative assessment of the antibacterial effect of nanoparticles was carried out using the dilution method and the determination of the minimum inhibitory and minimum bactericidal concentrations. It was found that the studied silver nanoparticles have sizes in the range from 5 to 24 nm with an average diameter of 10.8 nm. It was shown that all clinical strains of microorganisms used in the study are characterized by multiple antibacterial resistance, the percentage of antibiotic resistance for them ranges from 12.5 to 93.3 %. It was found that for the studied microorganisms the values of the minimum inhibitory concentration (MIC) are in the range from 7.81 to 31.25 μg/ml, and the minimum bactericidal concentration (MBC) is in the range from 31.25 to 62.50 μg/ml. The obtained data on MIC and MBC can be used to create promising antimicrobial drugs and medical devices of the next generation.