Data on mechanisms of resistance to antimicrobials in bacteria are reviewed and summarized. Main causes of resistance emergence and spread in bacteria are analyzed. Mechanisms of innate resistance of pathogenic bacteria (non-specific efflux pumps, antibiotic-inactivating enzymes and mechanisms serving as permeability barriers) are characterized. Mechanisms of acquired resistance are described: antibiotic modification or degradation; active removal of an antimicrobial from a bacterial cell – efflux (draining out); sequestration; target modification (bypass). The origin of antimicrobial resistance mechanisms in pathogenic bacteria is shown to be debatable. It is noted that producer microorganisms can directly transfer antimicrobial resistance genes to pathogenic bacteria, but a reliable link between this process and antimicrobial resistance spread has not been identified and proven so far. Horizontal gene transfer, including free DNA transformation, transduction by bacteriophages and plasmid-involving conjugation, is believed to play an important role in antimicrobial resistance spread. All three mechanisms are widespread in nature, although some bacterial species use one mechanism to a great extent than the other two. Transduction is supposed to play an important role, in particular, in the antibiotic resistance gene transfer, but the significance of transformation or transduction in the resistance gene transfer under the laboratory or environmental conditions has not been clarified so far due to the difficulty of naturally emerging recombination detection. Data on the role of conjugation in the antimicrobial resistance gene spread in nature, in particular carbapenem- and quinolone-resistance genes in gram-negative and gram-positive bacteria are presented. New trends in the antimicrobial resistance gene spread are indicated. 

The article presents data on the phenotypic and genotypic characteristics of antimicriobial resistance in Escherichia coli clinical isolates recovered from bovine microbiota (secretions from mammary glands, cervical swabs). 127 Escherichia coli isolates were studied, i.e. 44 from mammary glands secretions and 83 from cervical swabs. Disk diffusion method was used to study antimicrobial resistance of the cultures; minimum inhibitory concentrations of antimicrobials were determined in a serial dilution method; resistance genes were detected by polymerase chain reaction. The carried out research demonstrates a wide distribution of the isolates belonging to the phenotype resistant to ansamycins (rifampicin), semi-synthetic penicillins (ampicillin and amoxicillin), tetracyclines (doxycycline). The isolates showed a lower level of resistance to macrolides (azithromycin), amphenicols (levomycetin) and aminoglycosides (tobramycin). It was found that Escherichia coli clinical isolates are sensitive to third-generation cephalosporins and fluoroquinolone antimicrobials. However, since 28.46% of cultures demonstrate intermediate resistance to third-generation cephalosporins and 49.02% of Escherichia coli DNA samples isolated from mammal gland secretions had blaDHA gene associated with resistance to this group of antimicrobials, these antimicrobials could be hardly recommended as antibiotics of choice. Absence of VIM carbapenemase-encoding gene in the DNA of the recovered isolates and a low level of phenotypic resistance (10.22% of isolates from cervical swabs) can be one of the reasons for recommending first-line carbapenems as antibiotics of choice to treat animal diseases associated with Escherichia coli, along with fluoroquinolones as reserve antimicrobials. It was found that the recovered Escherichia coli isolates are more sensitive to combination antibiotics than to mono-antibiotics. 

The widespread use of antimycotic agents for the treatment of mycoses in humans and animals is of concern to medical and veterinary specialists due to the emergence of resistance of pathogenic and opportunistic fungi to antifungal agents. In recent years, information has been accumulated on the various molecular mechanisms underlying this phenomenon, but in-depth studies are needed to successfully predict resistance in various groups of fungi. To treat and prevent fungal infections several groups of antimycotics are used, where azoles and allylamines are the most frequent ones, which leads to resistance development in pathogenic and opportunistic fungi. The article presents the results of molecular methods identification of azole-resistant Candida albicans isolates and terbinafine-resistant Trichophyton isolates. The analysis of gene ERG11 nucleotide sequences of 10 Candida albicans isolates, recovered from different animal species, enabled the division of phenotypically resistant and susceptible strains, but could not differentiate between the strains, which have dose-dependent resistance to azoles. Study of single nucleotide polymorphisms in gene SQLE, associated with the resistance development to terbinafine in 12 fungal isolates of genus Trichophyton, did not allow grading them by their resistance, which is likely associated with another resistance mechanism, which can be observed in these strains. The results obtained can serve as a basis for the use of molecular methods to characterize fungi of Candida and Trichophyton genera, however, taking into account the biological features of pathogens from different groups it is reasonable to use several significant genome regions or the results of the whole genome sequencing, as well as the gene expression analysis for successful forecasting of potential resistance. 

The article provides data on antimicrobial resistance (AMR) of Salmonella isolates recovered from animal products tested in the Laboratory for Microbiological Testing of the FGBI “ARRIAH” from 2019 to 2020. 106 isolates of Salmonella enterica subsp. Enterica were recovered from 4,500 tested samples of raw materials and products of animal origin, 23% of them wereuntyped, and 77% belonged to 17 serological variants. Isolates of S. enteritidis (n = 37) and S. virchow (n = 9) serovariants dominated among the typed cultures of Salmonella, which is consistent with the data from other authors. Antimicrobial susceptibility of the microorganisms was determined in a disk diffusion test in accordance with the recommendations of the European Committee on Antimicrobial Susceptibility Testing. Different Salmonella serovars demonstrated different proportions of susceptible and resistant isolates, in terms of antibiotics from ten pharmacological groups. The largest number of polyresistant isolates was noted in Salmonella serovars S. virchow, S. nigeria, S. infantis, S. colindale. Both resistant and polyresistant Salmonella isolates were most often isolated from poultry products. S. typhimurium serovar, which is referred to in literature as polyresistant, was resistant to one or two antimicrobial agents as the research demonstrates. Isolates of 9 Salmonella serovars out of 17 (65%) showed resistance to nalidixic acid. 97% (n = 36) of S. enteritid isisolates were resistant to this antimicrobial agent. Isolates of S. Colindale serovar (n = 2) were resistant to 8 antimicrobials, S. papuana (n = 5) – to 6 antibiotics, and S. agona (n = 3) – to 5 antimicrobials. Untyped Salmonella isolates were resistant to 9 antibiotics, 2 cultures out of them showed resistance to ciprofloxacin. 

The purpose of the present study is to assess how cultivation conditions influence growth and formation of Pseudomonas aeruginosa biofilms. The topic is of great importance due to high incidence of P. aeruginosa-caused infections and P. aeruginosa resistance associated with its ability to form biofilms. The paper analyzes factors that influence biofilm formation, i.e.: growth phase used for inoculation (log, stationary), volume of the growth medium (0.2 and 1.0 ml) and concentration of nutrients (liquid nutrient media diluted to concentrations of 50; 25; 12.5 and 6%) in the cultivation volume. As the research demonstrates, all these factors influence biofilm formation; and a P. aeruginosa growth phase before inoculation is a determining factor in the biofilm formation. When P. aeruginosa is inoculated at a stationary phase, biofilm formation shows non-linear dependence on concentration of nutrients and on their total amount in the cultivation volume. The linear dependence of biofilm formation on concentration of nutrients in the culture medium is more pronounced, when P. aeruginosa is inoculated at a log phase. The study shows that lower concentrations of nutrient media components lead to more noticeable differences in biofilm formation, and such differences are statistically significant. Two-fold dilution of the liquid nutrient medium does not affect the intensity of biofilm formation; however, a 4 to 8-folddecrease in concentration of nutrients in 0.2 ml of cultivation volume in habited the biofilms formation. In 1.0 ml of the culture medium, the biofilm forms evenly, and in 0.2 ml of 4–8-fold dilution of nutrient medium it grows slower. The slow growth rate is statistically significant. The cultivation volume is also of great importance. For example, cultures grown in 0.2 ml of nutrient medium at different concentrations of nutrients formed fewer biofilms than microorganisms cultivated in 1.0 ml. At the same time, when inoculating P. aeruginosa both at log and stationary growth phases, biofilm formation is more pronounced in wells containing more cultivation volume. 

Data on the etiological structure of potential pneumonia agents in monkeys based on postmortem findings and subsequent bacteriological tests of lung tissues collected from the organ areas showing morphological changes are presented. In the period between 2019 and the first half of 2021, 377 animals died of pneumonia. The highest pneumonia-associated mortality was observed in newborn (0–8-day-old) and baby monkeys under the age of 1 month (161 animals). Polysegmental bronchopneumonia was detected in the dead monkeys in 94.4% of cases, croupous pneumonias accounted for 4.5%. Pneumonia was typically the only disease detected in baby monkeys. The microbial landscape in pneumonia affected monkeys was characterized by a broad diversity: 899 bacteria of different taxonomic groups were isolated from the lung tissues. Staphylococci (23.8%) prevailed among gram-positive bacteria, Escherichia coli (32.1%) – among gram-negative bacteria. Streptococcus pneumoniae made up 0.3%. Based on data from bacteriological tests, the proportion of pneumonias of undetermined etiology was 0.7%. Besides, bacterial associations, two- or three-component ones as a rule, were detected in the tests of lung tissue samples. The most frequent combinations of associative pathogens were the following: Escherichia coli + Proteus spp. (24.7%), Staphylococcus aureus + Escherichia coli (19.6%), Staphylococcus spp. + Enterococcus spp. + Escherichia coli (35.5%), Staphylococcus spp. + Escherichia coli + Proteus spp. (21.2%). Almost all the enterobacteria detected have a high associativity coefficient and occur mainly in the form of associations. The analysis of the study results showed that practically any microorganism alone or in combination can cause pneumonia in an animal with a weakened immunity; therefore, the effect of microbiota should not be underestimated. Also, significance of associative microbes in the development of pneumonia in captive monkeys is increasing. 

New method of post-mortem diagnosis of bovine leukosis is proposed and it involves use of agar gel immunodiffusion assay. The proposed method allows for the detection of antibodies against bovine leukemia virus (BLV) antigen located in the muscle and tissue fluids (plasma and lymph) of meat and offal. Post-mortem sampling was performed by dragging sterile cotton swabs across different parts of carcass and organs of both animals known to be seronegative and animals not tested alive. The collected samples and accompanied documents were submitted to the laboratory. 0.5–0.7 ml of isotonic solution (0.85% sodium chloride solution) were added to the tube with the swabs and the tube was left for 3–5 hours at 18–26 °C until homogenous substance formation. The tube was occasionally shaken so that BLV antibodies moved to the normal saline solution for further immunodiffusion assay. The assay results were visually recorded by detection of precipitation lines. Testing of 175 samples collected from animals not serologically tested for bovine leukosis before slaughter demonstrated five positive results (2.9%). Immunodiffusion assay of the tissue (lymphatic) fluid swabs collected from 148 animals, declared BLV seronegative alive in the veterinary certificates, demonstrated negative results. Therefore, along with autopsy, histological, molecular and genetic methods the immunodiffusion assay can be one of the tools for post-mortem diagnosis of bovine leukosis.

Animal microbiome plays a significant role in all the vital body processes. Studying the microbiome is essential for gaining a detailed insight into the interactions among microorganisms inhabiting a certain organ and their relationship with macroorganism cells. Evaluating the state of animal microbial community and its function can provide an invaluable assistance in seeking new strategies to improve feed efficiency and maintain cattle health. The aim of the study was to compare the taxonomic structure of the intestinal microbiome of Aberdeen Angus cattle imported to Kazakhstan with that of local breed cows using next generation sequencing technology. The tests of fecal samples allowed for determination of the complete microbial composition of animal intestinal contents, while leaving out the preliminary stage of microbiological cultivation using nutrient media. The results of 16S metagenomic analysis showed that Firmicutes and Proteobacteria were predominant bacterial taxons at the phylum level in the intestinal microbiome in both groups of animals, with their numbers being roughly the same. At the bacterial familylevel, the number of Clostridiaceae was a little higher in Aberdeen Angus cows (19.7%) than in the local breed cattle (15.4%). The representatives of the families Bacteroidaceae, Peptococcaceae, Ruminococcaceae and Coriobacteriaceae prevailed in the gut microbial community of local cattle. These microorganisms are involved in the synthesis of vitamins, they stimulate the immune function of the body, normalize digestion, improve nutrient utilization and thus contribute to body weight gain in animals. Small numbers (0.5%) of bacteria of the family Prevotellaceae were detected only in the local breed cows demonstrating high body weight gain. The microbiome of the local cattle was characterized by a considerable diversity at the genus level: the total number of taxons amounted to 65, whereas in Aberdeen Angus cattle it was 40. It was found that the intestinal microbiome of local breed cattle includes less methanogens and more acetogens. 

Modeling of potential nosoareals of sheep pox and goat pox that was performed in 2016 revealed a possible trend for aggravation of epizootic situation intensity with regard to these diseases up to 2020, but taking into account the cyclical fluctuations of the situation, it was assumed that the intensity level might reduce in 2017–2020. The highest frequency of reporting these nosounits was characteristic of regions with a higher probability of sheep pox and goat pox occurrence. The retrospective analysis was used to determine the structure, dynamics and properties of the epizootic process of these infectious diseases in the Republic of Tajikistan in 2000–2021. The main causes of sheep pox and goat pox outbreaks in the country were identified. The obtained results confirming the methodological validity of the epizootic situation analysis carried out in 2016 and correctness of the developed models of potential sheep pox and goat pox nosoareals, can become the basis for epizootological prediction of infectious disease risk when the pathogen interacts with susceptible animal population in specific climatic, socio-economic, organizational and managemental conditions. Based on systemic epidemiological analysis of the structure and dynamics of nosoareals, as well as risk assessment of sheep pox and goat pox entry, emergence and distribution, monitoring and establishment of infected and endemic zones, the features and patterns of distribution and occurrence of these diseases’ epizootic process were defined, which confirms the need for a systematic approach to epidemiological surveillance of highly dangerous and economically significant infectious diseases having a trend for transboundary spread, which will facilitate the solution of the problem regarding identification of possible threats and the implementation of veterinary and sanitary measures in case of disease occurrence in the territory of any country to ensure animal disease freedom. 

Data on tests of chickens for their immune responses to infection with low pathogenic А/Н9N2 avian influenza virus isolates belonging to Y-280 and G1 genetic lines are presented in the paper. CD4⁺/CD8⁺ ratios were determined with flow cytometry for initial immune status examination and for detection of apparent immune system disorders. Quantitative analysis of peripheral blood lymphocyte subpopulations in chickens revealed changes characteristic of the immune suppression. Analysis of dynamics of T- and B-lymphocyte levels in blood of the infected chickens revealed decrease in relative T-lymphocyte counts and increase in relative B-lymphocyte counts. T-lymphocyte subpopulation composition expressed as CD4⁺/CD8⁺ ratio (%) changed after the infection: CD4⁺ cell proportion was found to decrease whereas CD8⁺ cell proportion increased. According to literature data, immune response activated by vaccination induces the reverse dynamics towards to increase in CD4⁺/CD8⁺ ratio. Both cell-mediated immunity and humoral immunity play role in development of the immune response in chickens infected with avian influenza viruses. Apparent humoral immune response was detected by serological tests of sera taken from chickens on day 14 after infection. Mean specific anti-A/H9N2 AIV antibody titre in all groups of test chickens infected with low pathogenic avian influenza virus isolates was higher than 6 log₂ . High level of specific antibodies to avian influenza virus was indicative of postvaccinal humoral immune response development. 

The results of the phylogenic analysis of the nucleotide sequence of the IBDV A and B genome segments have been presented. Traditionally the IBDV isolates are classified based on the phylogenic analysis of the hypervariable region of the VP2 gene. The analysis of the VP2 gene segments of the isolates detected in the Russian Federation demonstrated that most of them belong to the genetic group comprising highly virulent IBDV isolates. However, not all isolates belonging to one genetic group have the same phenotypic characteristics. This is related to the fact that the virulence is determined not only based on the characteristics of the VP2 gene (A segment) but on the characteristics of the VP1 gene (B segment) as well. The IBDV genome segmentation allows formation of reassortant viruses which can be identified as a result of the genome segment analysis. The phylogenic analysis of the nucleotide sequences of VP2 and VP1 genes of 28 IBDV isolates detected at RF, Ukrainian and Kazakh poultry establishments in 2007 and 2019 showed that 15 of them are reassortant viruses. Different combinations of the genome segments have been identified among these reassortant viruses. Detection of different combinations of IBDV genome segments is indicative of the fact that the heterogeneous virus population circulates on the poultry farms. Pathogenicity studies of the three IBDV isolates showed that the most virulent was an isolate having two genome segments characteristic of the highly virulent virus. Two reassortant viruses having only one genome segment A or B, characteristic of the infectious bursal disease, demonstrated less pronounced virulent properties. 

Animal management and breeding as well production, transportation, preparation, and processing of animal products and raw material result in generation of a considerable amount of biological wastes being a source of biological contamination of the environment and a clear threat to human and animal health. The animal biowaste incineration units are high threat facilities and require constant surveillance and control. Collection and analysis of data provided by the RF veterinary executive authorities were performed to objectively reflect the actual situation of the biological waste incineration facilities in the RF Subjects and to create a holistic view on the problem of interest in the country. The following parameters were analyzed: their number, type (stationary and mobile), type of ownership, location, availability of the certificate and highly-qualified specialists serving the biological waste incineration equipment as well as the availability of such facilities in the RF Subjects as for January 1, 2021. The analysis demonstrated that 4,459 biowaste incinerators were registered in the country. Most of these units are stationary and they belong to establishments involved in farm animal keeping, animal product processing, production and storing. Such equipment is mostly serviced by non-qualified staff ignorant of the technical characteristics and operating principles of this equipment. Almost one third of these units in the country are home made that is why their use does not guarantee complete destruction of biological wastes and pathogen inactivation. It was also revealed that the procedure for the incineration of biological waste of animal origin using home made incinerators is not legally fixed in the country. The results obtained show that the situation of the animal biowaste incineration in the Russian Federation is quite complicated.