Molecular mechanisms and genetic determinants of resistance to antibacterial drugs in microorganisms (review)

The emergence of antibiotic resistance is a serious public health problem, since antibiotic-resistant bacteria that develops in conditions of agro-industrial enterprises can easily transmit to humans through products and raw materials of animal origin and contaminate the environment with agricultural waste. Several reviews cover the problem (C. Manyi-Loh et al., 2018; A.N. Panin et al., 2017). A significant number of publications describe the mechanisms of antibiotic resistance, including modification of the target affected by the drug; the acquisition of metabolic pathways alternative to those inhibited by an antimicrobial agent; overproduction of the target enzyme; enzymatic inactivation and active efflux of the antibiotic (it’s excretion outside the microbial cell). These mechanisms can be natural for some microorganisms or acquired from other microorganisms (M.F. Varela et al., 2021; W.C. Reygaert, 2018; A.L. Bisekenova et al., 2015). Understanding these mechanisms will allow us to choose the best treatment option for each specific infectious disease and develop antimicrobial drugs that prevent the spread of resistant microorganisms. The most clinically significant antibiotic resistance genes are usually located on different mobile genetic elements (MGE) that can move intracellularly (between the bacterial chromosome and plasmids) or intercellularly (within the same species or between different species or genera) (C.O. Vrancianu et al., 2020). Among the three main mechanisms involved in horizontal gene transfer, transformation of antibiotic resistance genes between bacterial species happens rarely. However, conjugation with the participation of mobile genetic elements, such as transposons and plasmids, is the most effective and important method of spreading antibiotic resistance (J.M. Bello-López et al., 2019). The purpose of this review is to describe antibiotic resistance genes distinctive for the microbiota of farm animals under the conditions of the agro-industrial complexes, as well as the mechanisms of the formation of antibacterial resistance to antimicrobial drugs used in veterinary medicine. In addition, this report covers the direct localization of the genetic determinants of antibiotic resistance, outlines the main measures to control antibiotic resistance, which include i) reducing the use of antibiotics due to improving animals' welfare and living conditions and ii) monitoring and supervision of the spread of antibiotic-resistant bacteria.