Phenotypic and molecular genetic methods to determine antibiotic resistance of microorganisms in veterinary medicine

The paper presents scientific approaches to solving a global problem, namely the increasing antibiotic resistance among opportunistic and weakly pathogenic microorganisms, which pose a significant risk both in human medicine and in animal husbandry. In this regard, phenotypic, analytical and molecular methodological methods for determining and studying the antibiotic resistance of microorganisms are presented. Of the phenotypic methods, the method of standard disks and the method of serial dilutions, which are based on the diffusion of antibacterial drugs from the carrier onto a solid nutrient medium and inhibition of the growth of the studied culture of the microorganism, have received wide application. Among the analytical methods for detecting antibiotic resistance, electrophoretic, immunochemical (immunochromatography), UV and mass spectrometry are distinguished. The most promising and effective is mass spectrometry, in particular the MALDI-TOF test, which is the most optimal for routine determination of the sensitivity of a number of cultures of microorganisms. The molecular approach, namely the use of PCR using molecular beacons and DNA genes, expands the possibility of monitoring the resistance of microorganisms, and makes it possible to determine the mechanism of formation of resistance to antibacterial drugs by the presence of resistance genes. The analysis of methodological approaches made it possible to identify the following determinants of resistance: carbapenemase in Enterobacterales spp, P. aeruginosa and Acinetobacter; Extended-spectrum B-lactamases in Enterobacterales; mcr-mediated encoded resistance to polymyxins in gram-negative microorganisms; mecA/mecC, mediated resistance to beta-lactams in S.aureus; and vanA/vanB, mediated resistance to glycopeptides in E. faecium and E. faecalis. An analysis of the data of available scientific publications allows us to state that different methodological approaches provide different accuracy in indicating variants of resistance determinants. It should be noted that the presence of several databases of antibiotic resistance genes makes it difficult to use them to determine the phenotype of drug sensitivity. However, the use of genomic data to determine antibiotic resistance is crucial for the development of clinical metagenomics.