Today, antimicrobial resistance is the number one problem worldwide. According to the latest data, it has found that Acinetobacter baumani, Pseudomonas aeruginosa, Klebsiela pneumonia and Enterobacter cloacae are predominant among all isolated resistant pathogens. So, the search of a new antibacterial drug that can deal with antimicrobial resistance is task number one.

Aim. The study aimed to investigate theoretical and practical relationship of structure and antibacterial activity of quercetin and rutin against test Gram-negative strains: Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris, and clinical resistant strains such as Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, Enterobacter cloacae.

Materials and methods. The research subjects were quercetin and rutin. The theoretical research was carried out using AutoDockTools 1.5.6; antibacterial effects were evaluated by the well method. Clinical strain of P. aeruginosa, A. baumani, K. pneumonia, E. cloacea were taken from tracheal aspirate and bronchoalveolar lavage.

Results. Theoretical studies showed that none of the investigated antimicrobial drugs inhibit all “targets” mechanism of antibacterial action. Rutin revealed high selectivity to DNA-gyrase, dihydrofolate reductase (DHFR), deacetylase, AHS RhI, Diguanylate cyclase, unlike quercetin which revealed low selectivity. Experimental research demonstrated that against P. aeruginosa rutin and quercetin inhibited growth – 17.0 ± 0.4 mm and 18.0 ± 0.4 mm, against P. vulgaris – 14.0 ± 0.5 mm and 16.0 ± 0.5 mm, against E. coli – 16.0 ± 0.5 mm and 20.0 ± 0.4 mm, respectively. Resistant strain of P. aeruginosa, E. cloacea, A. baumani, K. pneumonia were sensitive to the action of rutin – 23.0 ± 0.3 mm, 25.0 ± 0.2 mm, 24.0 ± 0.3 mm, 23.0 ± 0.3 mm, respectively, while to the action of quercetin resistant strain were low sensitive – 12.0 ± 0.6 mm, 14.0 ± 0.5 mm, 12.0 ± 0.6 mm, 12.0 ± 0.6 mm, respectively.

Conclusions. Theoretical studies of “standard” antimicrobial drugs used in infectious disease treatment protocols are not highly selective inhibitors of “target” antibacterial mechanisms of gram-negative bacteria, unlike rutin, which turned out to be a highly selective inhibitor. According to the results of the theoretical study, it was found that the potential antibacterial activity of rutin exceeds the effect of quercetin by two times. This pattern is fully confirmed by in vitro studies, where the antibacterial effect of rutin against resistant strains was also two times higher.