The purpose of this review was to analyze the findings of domestic and foreign researchers on the development of modern drugs for the specific prevention of plague and to illustrate the possibilities of using bioinformatics analysis at the design stages to create an effective and safe vaccine. Work on the creation of an effective new-generation plague vaccine is hampered by several factors associated primarily with the presence of mechanisms of evasion from the immune system of the macroorganism, as well as a large number of pathogenicity determinants in the plague agent. Due to the development of approaches that are based on in silico studies, there is a progressive development of vaccine technologies oriented primarily to the use of the most important immunogens of the plague microbe (F1 and V antigen). Studies aimed at improving the antigenic properties of F1 and LcrV, as well as work on bioinformatic search and analysis of additional promising components to be included in the composition of subunit vaccines are considered as topical applications of bioinformatics data analysis in developing the tools for enhancing the effectiveness of protection through vaccination with subunit preparations.

This review systematizes and analyzes the data published over the past decade, devoted to the study of low-molecular-weight high affinity iron chelators – siderophores. Siderophores, which are found in bacteria, fungi and mammals, are able to extract iron from insoluble inorganic compounds, and in the host organism – from complexes with proteins that perform the function of nonspecific protection of mammals from infections. The extracted iron is delivered to cells through surface protein receptors specific for each siderophore, as well as various protein transport systems that make up membranes. Siderophores play an important role in virulence in pathogenic bacteria, performing many functions in the host organism, in addition to providing microbes with iron and other biological metals. They participate in the storage of excess iron, toxic to cells, protect bacteria from reactive oxygen compounds, compete for iron with phagocytes, and have a harmful effect on host cells, acting as secreted bacterial toxin in some cases. Bacterial siderophores perform a signaling function and regulate both, their own synthesis and the synthesis of other virulence factors. Many pathogenic bacteria produce several siderophores that are active under different conditions, against various sources of iron in the host organism and at different stages of infectious process. The review presents the results of the experimental studies aimed at elucidating the structure and diverse functions of bacterial siderophores, the mechanisms of their biosynthesis and regulation of expression, as well as the role of these molecules in the physiology and virulence of pathogenic bacteria. Special emphasis is put on siderophores of bacteria causing particularly dangerous infections.

Yersinia pestis strains of the 1.ORI lineage originate from China as a result of evolution of the 1.ANT phylogenetic branch. Strains of the biovar orientalis are divided into three major lines of evolution: 1.ORI1, 1.ORI2, 1.ORI3. Lines 1.ORI1 and 1.ORI2 originated in China and then spread across the east and west coasts of India, respectively. Strains of the biovar orientalis have widely spread throughout the world, mainly as a result of introduction by sea. This way, the 1.ORI1 line was imported onto the territory of North America. 1.ORI2 line has spread to Southeast Asia, Africa, Europe, and South America. In addition, the strains of the biovar orientalis were brought to the territory of Australia, however, the formation of natural foci did not occur. The spread of strains to new territories during the third plague pandemic, as a rule, took place with the participation of one strain, which caused epizootics among synanthropic rodents. After that, outbreaks were recorded among the population of port cities, followed by drifting into the countryside and the formation of natural foci under suitable natural conditions. In the absence of such, the plague pathogen was eliminated from natural biotopes, and the formation of a natural focus did not occur. In recent decades, most cases of human plague in the world have been caused by strains of the biovar orientalis (1.ORI). However, the emergence and spread of the evolutionary line “1” is insufficiently studied. Currently, there is a lack of both historical data and strains that are ancestors of modern strains in many countries to clarify the details of the irradiation of strains of the biovar orientalis. As a result, the concepts of dissemination of many evolution branches of the strains, biovar orientalis are in the form of hypotheses to date. In this work, the collection and analysis of literature data on the history and epidemiology of plague over the third pandemic, a search for a connection between epidemic manifestations and the appurtenance of the strains that caused them to certain phylogenetic lineages was carried out.

The aim of the review is to show the groundlessness of the unconditional assessment of rhamnose-positive strains of plague pathogen as avirulent for most species of carriers and humans and having no epidemiological significance. The main carriers of rhamnose-positive strains are several species of voles and the Mongolian pika. The vast majority of experts are of the opinion that rhamnose-positive (“vole`s” and “pika`s”) strains of Yersinia pestis are avirulent or weakly virulent for many species of warm-blooded animals and humans, and therefore have no epidemiological significance. However, in a series of experiments on infecting marmots, ground squirrels, and large gerbils with rhamnose-positive strains, some of the experimental animals fell ill acutely and died from the plague. In nature, rhamnose-positive strains have been isolated from carcasses of relatively resistant red marmots. When evaluating the epidemiological significance of rhamnose-positive strains, such an important criterion as the presence or absence of effective factors and pathways of pathogen transmission in foci of the vole and pika types is omitted. Voles and pikas are not eaten; therefore, the contact route of infecting humans in these foci is impossible. The second way of transmission of the pathogen to humans – vector-borne – is difficult due to the lack of migration of vole fleas from burrows to the surface and their low efficiency as vectors. Nevertheless, cases of human infection with rhamnose-positive strains of the plague agent in the Caucasus and Mongolia give grounds to assert that at least some rhamnose-positive strains have a sufficiently high virulence and are capable of causing infectious process in humans as well. Therefore, epidemiological surveillance in the foci of plague of the vole and pika types cannot be totally abandoned. It can be conducted according to an abbreviated scheme.

Tick-borne viral encephalitis (TBVE) is one of the most significant natural-focal infections in the Russian Federation.

The aim of the study was to analyze the current epidemiological situation on TBVE in the Buryat Republic in 2010–2020 with a subsequent differentiation of municipalities by epidemiological risk groups in order to elaborate proposals for optimization of preventive measures.

Materials and methods. A retrospective analysis of the epidemiological situation on TBVE in the Buryat Republic was carried out using forms of federal statistical surveillance No. 2 “Information on infectious and parasitic diseases” over 2010–2020 and the data from the Reference Center of the Irkutsk Research Anti-Plague Institute of Siberia and Far East of the Rospotrebnadzor on the epidemiological situation and preventive measures in the municipalities of the constituent entity. Statistical processing was performed applying conventional methods of variation statistics. Based on calculated 95 % parametric confidence interval for the data on variability of the long-term average TBVE incidence in the municipalities of the Republic of Buryatia over a 10-year period, the entities were differentiated by epidemiological risk groups. QGis 2.18.28 and a set of open geodata OpenStreetMap were used for mapping.

Results and discussion. All municipalities have been classified into five groups by the level of epidemiological risk: with zero TBVE incidence – 2 districts, with a low level – 4, medium – 8, high – 5, very high – 2. In addition, the administrative center has been placed into a separate group. Each individual group of municipalities is characterized by the number of TBVE cases, the level of morbidity, the frequency of seeking medical aid because of tick bites, the scope of specific and non-specific prevention measures. Recommendations for optimizing the tactics of TBVE prevention in certain municipal districts have been provided.

Cellular immunity plays an important role in the pathogenesis and formation of protective immune defense against the SARS‑CoV‑2 virus.

The aim of the work was to study the cellular immunity of rhesus monkeys applying flow cytometry after experimental infection with the SARS‑CoV‑2 virus.

Materials and methods. Male rhesus monkeys were intranasally inoculated with the SARS‑CoV‑2 virus, Isolate B strain and hCoV-19/Russia/SP48-1226/2020 strain (abbreviated name U-2), at a dose of 5.0 lg PFU. Using flow cytometry, the levels of 21 populations/subpopulations of mononuclear cells in the peripheral blood of animals were determined before experimental infection with the pathogen and on day 14 after infection. SARS‑CoV‑2 coronavirus RNA was assessed using real-time polymerase chain reaction. Determination of the titer of virus-neutralizing antibodies to the SARS‑CoV‑2 virus in the blood sera of animals was conducted through neutralization test evaluating the ability to suppress negative colonies.

Results and discussion. Infection with Isolate B strain culture has led to an increase in the relative content of total T-lymphocytes (p˂0.2), cytotoxic T-lymphocytes (p˂0.1), as well as monocytes expressing the early activation marker CD25 (p˂0.2). The decrease in levels has been observed for total B-lymphocytes (p˂0.2) and T-helper cells (p˂0.1). Infection with the U-2 strain culture revealed an increase in the relative content of monocytes expressing the early activation marker CD25 (p˂0.2). Thus, for the first time in the Russian Federation, flow cytometry was used to study the cellular immunity of rhesus monkeys before and after experimental infection with the SARS‑CoV‑2 virus. The obtained information can be used for studying the pathogenesis of SARS‑CoV‑2 infection, course, and outcome of the disease, and developing strategies for vaccination and treatment.

The purpose of the work was to analyze the phylogenetic relations and origin of Yersinia pestis strains isolated in different periods of epizootic activity of the Caspian sandy natural focus (CSNF) of plague in the XX–XXI centuries.

Materials and methods. We used 40 Y. pestis strains from CSNF and adjacent plague foci, isolated in 1922–2015. Carried out was whole genome sequencing of 19 Y. pestis strains from CSNF. Phylogenetic analysis was performed using whole genome SNP analysis based on 1914 identified SNPs. The search for marker SNPs was conducted using the Snippy 4.6 software. The phylogenetic tree was constructed using the Maximum Likelihood algorithm, the GTR nucleotide substitution model.

Results and discussion. The whole genome SNP analysis has revealed that Y. pestis strains of the medieval biovar from CSNF belong to 2.MED1 phylogenetic lineage and fall into two major branches. One of them circulated in the focus in the first half of the XX century, and the other – in the second half of the XX – early XXI centuries. It is shown that strains of the first branch were the cause of outbreaks and individual cases of plague in the CSNF in the first half of the XX century. They are closely related to strains from the Caspian North-Western steppe and Volga-Ural sandy natural plague foci, which caused numerous outbreaks with high mortality rate in the same period. Y. pestis strains from the CSNF of the second half of the XX and early XXI centuries belong to the second phylogenetic branch of the 2.MED1 line, at the node of which the strains from the Northern Aral Sea region of 1945 lay. The latter were the predecessors of all strains isolated in the CSNF after a long inter-epizootic period that occurred in the middle of the XX century. There can also be traced a genetic relation between the strains from CSNF and the Dagestan plain-foothill focus.

The aim of the study was to increase the efficiency of decontamination of biological material and media (by the example of food products) by pulsed (non-thermal) radio emission and asses the prospects of its application in medicine and biology.

Materials and methods. To achieve the goal an experimental setup has been designed, manufactured and tested, which makes it possible to study the process of exposure of biological materials and media to pulsed (non-thermal) radio emission, in particular, by the example of food products. The basis of the method is optimum control of the electro-physical parameters of the irradiating radio signal, depending on the type of the irradiated object. We used pulsed magnetrons with operating frequency of (2.45±0.05) GHz, authorized for bio-medical research, generating pulsed radiation with an adjustable power within the range of 0.1...10 kW. The pulse repetition rate with a duty cycle of 500...10000 is 0.1...5 kHz. The setup has an operating chamber into which the test sample is placed, as well as additional elements of magnetron protection and measuring the parameters of the microwave power incident on biological object.

Results and discussion. The setup has been successfully used to irradiate various food samples with pathogenic micro flora (Salmonella spp. etc.) with pulsed microwave radiation. In particular, as shown by the studies, the arithmetic mean number of pathogenic bacteria in the irradiated samples of minced meat decreased by 27.5 times after 28 days of storage as compared to the control group of non-irradiated samples. Preliminary conducted experiments in the field of investigating the effect of microwave radiation on the process of cell division and other aspects of electromagnetic field influence on pathological microorganisms confirm the prospects and the expediency of continuing the ongoing studies in medicine and biology. 

The aim of study was to conduct epizootiological monitoring of natural tularemia foci of the steppe type and investigate epizootic activity in the south-east of the Rostov Region.

Materials and methods. An epizootiological survey was carried out on the territory of Remontnensky, Sal’sky and Peschanokopsky districts of the Rostov Region in 2019–2021. To capture and collect mammals, Ixodidae ticks and to study the samples of field material conventional methods were used.

Results and discussion. Habitation of 16 species of small mammals, 6 species of Ixodidae ticks has been found. Molecular-genetic analysis of the voles has revealed the presence of the species Microtus arvalis obscurus in the studied area of the region. The circulation of the tularemia agent has been established in the population of common and social voles, forest mouse, hare, rook, Dermacentor marginatus, Hyalomma marginatum, removed from rooks. In May 2020, a high increase in the number of the social vole in the Remontnensky district (up to 21 %), in July 2020 – the common vole in the agrocenoses of the Sal’sky district (up to 33 %) was observed. An extensive epizooty of tularemia was detected in the population of common vole in the south-east of the Rostov Region and in adjacent territories in the Republic of Kalmykia and the Stavropol territory. Two cultures of the pathogen were isolated from the fallen and captured social voles, and four cultures – from the common vole. The isolated strains belong to the Holarctic subspecies of Francisella tularensis EryR. The results obtained attest to the activation of the natural tularemia focus in the south-east of the Rostov Region and its high epizootic activity.

The aim of the work was to study the profile of antibiotic resistance of uropathogenic Escherichia coli strains isolated from patients with urinary tract infections in the urological inpatient facility of the clinical hospital in the Saratov city, depending on appurtenance to phylogenetic groups and subgroups, as well as O-serogroups.

Materials and methods. We assessed sensitivity/resistance to 25 different antibacterial drugs in 102 strains of uropathogenic E. coli. The studies were carried out using the disk diffusion method. The production of extended spectrum beta-lactamases was evaluated by the double disk method. Carbapenemase output was determined using the CIM test. The PCR method was applied to determine appurtenance to phylogenetic groups and subgroups, O-serogroups, as well as the frequency of occurrence of the mcr‑1, mcr‑2, mcr‑3, mcr‑4, mcr‑5 genes encoding the proteins that mediate the development of resistance to colistin.

Results and discussion. It has been established that all strains of uropathogenic E. coli are more or less resistant to antibacterial drugs. All studied 102 strains showed resistance to 23 antibacterial drugs from 8 functional groups. The resistance of uropathogenic E. coli had certain differences depending on belonging to phylogenetic groups and subgroups, O-serogroups. Strains of uropathogenic E. coli with high resistance (up to 100 %) belonged to the B2₃ phylogenetic group, the main representatives of which are cultures of the most common O-25 serogroup. The production of extended-spectrum beta-lactamases has been phenotypically confirmed for 69 (67.6 %) strains. No carbapenemaseproducing cultures were found in the study. The mcr‑1 and mcr‑2 genes encoding resistance to colistin have been identified in 3 uropathogenic E. coli strains (2.9 %).

The aim was to present the experience of using mobile laboratory for monitoring and diagnostics (MLMD) during the epizootiological monitoring of the northern provinces of Vietnam. MLMD was transferred by Federal Service for Surveillance in the Sphere of Consumers Rights Protection and Human Welfare to the Socialist Republic of Vietnam as part of implementation of cooperation programs on combating infectious diseases. The use of MLMD made it possible to obtain new information on the circulation of pathogens of natural-focal infectious diseases on the territory of Vietnam. It also provided the necessary conditions for conducting research using methods of express diagnostics, bacteriological analysis, performing a full cycle of work – from the receipt of samples to the disinfection and destruction of infected material in compliance with the requirements of biological safety in the field. The effectiveness of using mobile laboratories in response to the emergencies of sanitary and epidemiological nature, both to strengthen stationary laboratory bases and to organize diagnostic studies in remote regions, has been shown. The use of MLMD for the diagnosis of COVID‑19 has been an effective component of countering the new coronavirus infection in Vietnam and significantly increased the volume of testing in the country.

The most important component of strengthening the potential for responding to biological threats both at the national and interstate levels is the formation of a unified system for monitoring and responding to emergencies (ES) of sanitary-epidemiological nature in the CIS territory.

The aim of the work was to review the systems for monitoring and responding to emergencies of sanitary-epidemiological character in the CIS countries by the example of the Russian Federation, the Republic of Belarus, the Republic of Kazakhstan and the Kyrgyz Republic, to characterize the main areas of international cooperation on countering biological threats and coordinating international response measures in the CIS countries.

Materials and methods. Information and analytical materials provided by organizations responsible for epidemiological surveillance and control in the CIS countries, Internet sources, and publications were used for the study.

Results and discussion. The organization and functioning of the systems for monitoring and responding to emergencies in the CIS countries is a state function. It includes, as a rule, the national, regional (sub-national) and territorial (local) levels, which have horizontal and vertical connections. The legal framework is made up of documents of the legislative level. Interdepartmental interaction in response to emergencies is carried out both at the republican level and in administrative territories; the basis for interaction is the integrated planning of preventive and anti-epidemic measures and the functioning of the relevant organizational structures on an ongoing basis. Since 2015, with the support of the Government of the Russian Federation, programs have been implemented aimed at assisting partner countries in the implementation of the International Health Regulations (2005) in order to increase national response capacity and form a unified sanitaryepidemiological emergency response system in the CIS countries. The main areas of collaboration are strengthening the material and technical base and human resources of specialized institutions and scientific cooperation. As a result of the program implementation, a unified system for monitoring and prompt response to emergencies in the field of public health of sanitary-epidemiological nature has essentially been formed in the CIS countries to date, uniting more than 15 specialized institutions from 8 CIS countries.

The aim of the study was to retrospectively analyze the range of variability of antigenic properties and genotypic characteristics of Vibrio cholerae R-variant strains atypical in terms of agglutinability.

Materials and methods. 169 strains of V. cholerae R-variant with atypical agglutinability have been studied using the “AmpliSens® Vibrio cholerae-FL” test-system. The determination of O1 antigen was carried out using the “Ig-V. cholerae О1/О139 – ELISA/dot-ELISA” reagent kit.

Results and discussion. A retrospective analysis of the complex of phenoand genotypic characteristics of strains isolated from surface water bodies in the territories of three former Soviet republics and 13 constituent entities of the Russian Federation in the course of 30-year monitoring and identified upon isolation as nontoxigenic V. cholerae R-variant strains has been performed. Upon re-identification, it was found that the strains belong to both epidemically dangerous (3.0 %) and non-dangerous strains (97.0 %). The range of variability was expressed in their distribution into three groups and consisted in retaining of agglutinability only with cholera RO serum in the first group (34.5 % of strains); the loss of this trait, but the acquisition of the ability to agglutinate in different combinations with O1, Ogawa or Inaba sera – in the second (16.7 %); and also in the loss of agglutinability with all diagnostic cholera sera – in the third (48.8 %). The presence of the wbeT gene in the compared V. cholerae classical R-variant strain does not exclude the presence of the genomic region for O1 antigen biosynthesis in other R-strains, possibly in a modified form, which can be clarified in further molecular-genetic studies. Alternatively, such strains are likely to be attributed to V. cholerae nonO1/nonO139. Strains of V. cholerae R-variant with different amounts of surface antigen (optical density range – from 0.088±0.002 to 1.226±0.003) have been identified. The data obtained can be used for monitoring of cholera in laboratories of regional and federal levels.

The aim of the study was to investigate the features of resistance formation in Burkholderia pseudomallei to quaternary ammonium compounds, as well as to analyze its influence on the development of antibiotic resistance.

Materials and methods. 10 strains of melioidosis causative agent with typical cultural and morphological properties have been studied. The selection of variants resistant to benzalkonium chloride was carried out by successive passages on a dense nutrient medium with the addition of a disinfectant in increasing concentrations. The determination of sensitivity to benzalkonium chloride was performed through serial dilutions in agar, to antibacterial drugs from the groups of sulfonamides, β-lactams and tetracyclines – using disk diffusion method. Statistical processing of the obtained results was conducted with the help of the Microsoft Excel 2019 software. Arithmetic mean values and errors of mean values were calculated. The significance of differences between the parameters was determined applying Student’s t-test.

Results and discussion. All parental strains showed a similar degree of resistance to the disinfectant compound and most of the strains – susceptibility to the antibiotics tested. Cultivation of B. pseudomallei strains on a nutrient medium with the addition of benzalkonium chloride led to an increase in resistance to this disinfectant. In addition, an increase in the level of resistance to all studied antibiotics was found. Statistical processing of the data collected revealed a significant correlation between the change in sensitivity to benzalkonium chloride and the emergence of resistance to amoxicillin/ clavulanic acid and ceftazidime. It was found that the causative agent of melioidosis, with a natural high susceptibility to benzalkonium chloride, has a high potential for developing resistance to this disinfectant compound, which is of practical importance in the development of disinfection regimens using quarternary ammonium compounds. For the first time, a direct correlation between a decrease in the sensitivity to benzalkonium chloride in B. pseudomallei and emergence of resistance to amoxicillin/clavulonic acid and ceftazidime has been demonstrated.

The aim of the study was to determine the tropism of the human immunodeficiency virus in patients with virological failure of antiretroviral therapy (ART) from the Arkhangelsk Region based on the analysis of the env gene V3 loop nucleotide sequence.

Materials and methods. We used blood plasma samples obtained from 76 HIV-infected persons from the Arkhangelsk Region with virological failure of antiretroviral therapy. The nucleotide sequences of the HIV env gene C2-V3-C3 region were studied by PCR followed by sequencing. The genotype of the studied strains was determined based on the analysis of their phylogenetic relations with reference sequences from the international GenBank database, as well as using specialized programs. To predict viral tropism, the Garrido rule and the online bioinformatic tool Geno2Pheno[coreceptor] were used. The Geno2Pheno[coreceptor] algorithm, determines the false positive rate (FPR) based on the analysis of the env gene V3 loop nucleotide sequence. Results and discussion. Significantly lower representation of R5X4/X4-tropic HIV variants in long-term infected persons with subsubtype A6 virus compared to subtype B virus has been shown. For all FPR cut-off algorithms, a significant correlation between subtype and HIV tropism was observed (p=0.0014 and p=0.013 for FPR 10 % and FPR 20 %, respectively). While among subtype B strains, at least 57 % were identified as R5X4/X4-tropic variants (for an FPR of 10 %), including two strains classified as X4-tropic; among HIV subsubtype A6 even at an FPR of 20 %, the frequency of R5X4/X4-tropic samples only slightly exceeded 22 %. It can be assumed that the dynamics of changes in HIV tropism depends on the virus subtype. Significant differences in the distribution of amino acid residues of the V3 region sequences in the examined group between R5-tropic and R5X4/X4-tropic strains of subsubtype A6 for positions 18 (χ2=7.616, p=0.0058), 21 (χ2=7.281, p=0.007), 24 (χ2=5.587, p=0.0181), and 34 (χ2=5.144, p=0.0233) have been demonstrated. Among the R5X4/X4-tropic strains of the A6 subsubtype, amino acid substitutions were registered at positions 6, 19, 21, 26, 29, 30, which were not found in the R5-tropic A6 strains. The high occurrence frequency of a number of mutations previously described as presumably associated with resistance to maraviroc and similar drugs may indicate a natural polymorphism characteristic of the A6 subsubtype, which does not correlate with resistance to CCR5 co-receptor antagonists.

The aim of the work was to characterize the epidemiological and epizootic situation on anthrax among population and animals in the Republic of Tatarstan over a period of 1920–2020.

Materials and methods. The analysis of the epidemiological and epizootic situation is based on the archival data, epidemiological maps of anthrax patients, results of epizootiological-epidemiological survey of anthrax foci conducted by the Rospotrebnadzor Administration in the Republic of Tatarstan and Center of Hygiene and Epidemiology in the Republic of Tatarstan, materials of the Main Directorate of Veterinary Medicine of the Republic of Tatarstan. Microbiological studies of samples from patients and environmental objects were performed in accordance with the requirements of MR 4.2.2413-08 “Laboratory diagnostics and detection of anthrax pathogen”, real-time PCR was set using the AmpliSense Bacillus anthracis-FRT test-system (Central Research Institute of Epidemiology, Moscow). Statistical data processing was carried out using the quantile ranking method.

Results and discussion. There are more than 1000 anthrax soil foci in the Republic of Tatarstan, which territorially belongs to the Volga Federal District. Analysis of the epizootic and epidemiological situation in the Republic of Tatarstan over the period of 1920–2020 has revealed that it has undergone significant changes, from mass diseases in animals and humans in early 20th century to sporadic cases of infection among population and animals at the beginning of the 21st century, primarily due to preventive veterinarysanitary measures, including veterinary and sanitary examination of animal products, mass specific immunization of animals against anthrax, arrangement of anthrax cattle burial grounds. In view of the improvement of epizootiological situation and implementation of preventive measures, there was a decrease in the incidence of anthrax among the population. The regions of the Republic have been ranked by the number of animal anthrax cases.

The aim of the study was to improve the methods for verifying the vaccine strain Francisella tularensis 15 NIIEG during long-term storage under current conditions.

Materials and methods. The paper summarizes the results of studying the phenotypic and genetic properties of lyophilized cultures of the vaccine strain F. tularensis 15 NIIEG (1953, 1966, 1969, 1987, 1990, 2003, 2012 and 2013) stored at SCEMAP for a period of one to 60 years.

Results and discussion. Previous studies have revealed that freeze-dried cultures of F. tularensis 15 NIIEG generally had the characteristics of the vaccine strain, with the exception of deviations from the regulatory requirements for residual virulence and specific safety. The stability of preservation of deletions in the pilA and pilE genes (the region of differentiation RD19) and the genes encoding lpp lipoprotein (RD18) in the vaccine strain, which was stored for various periods of time in a lyophilized state, has been confirmed. The vaccine-strain-specific mutation C178404T (by the genome of F. tularensis LVS strain, GenBank NCBI no. CP009694) has been identified, and an approach to determine it has been developed. The data obtained are promising as regards using the above deletions in the RD18/RD19 regions in combination with the C178404T mutation to assess the authenticity of the vaccine strain using molecular genetic methods. Thus, the conducted retrospective analysis of the data on the cultures of tularemia microbe vaccine strain from the 1940s to 2013 and the gathered experimental data, made it possible to supplement the uniform requirements for the manufacture, study, maintenance, storage and movement of F. tularensis 15 NIIEG vaccine strain with new evidence. Based on the results obtained, the authors have drawn a draft methodological recommendations of the federal level “Vaccinal strain Francisella tularensis 15 NIIEG: order of handling”.

The aim of the study was to evaluate the effectiveness of MALDI‑ToF mass spectrometry in the identification of collection and newly isolated strains of tularemia pathogen using the database “Protein profiles of mass spectra of microorganisms belonging to I–II pathogenicity groups for the MALDI Biotyper software”.

Materials and methods. We investigated 142 strains of Francisella tularensis, including 59 collection strains and 83 newly isolated ones. Bacteriological, molecular-genetic and proteomic research methods were used to identify them. The acquisition of mass spectra, analysis, generation and expansion of reference libraries were performed on a mass analyzer “Microflex LT” using FlexControl v. 3.3, FlexAnalysis v. 3.3, and MALDI Biotyper 3.0 software packages. The cluster analysis was performed using the BioNumerics 7.6 software.

Results and discussion. The possibility of identifying tularemia pathogen has been assessed using the extended database for MALDI Biotyper 3.0 “Protein profiles of mass spectra of microorganisms belonging to I–II pathogenicity groups for the MALDI Biotyper software”. During identification to the species level, the significance of mass spectrometry results for collection strains and newly isolated ones was 91.5 % and 97.6 %, respectively. In determining the genus appurtenance, the reliability of identification was 100 %. Thus, the MALDI‑ToF mass spectrometry method allows for accurate species and genus identification of F. tularensis strains. Based on the cluster analysis of 66 F. tularensis strains in BioNumerics 7.6 software using «Pearson correlation» and the UPGMA algorithm, the possibility of subspecies differentiation has been evaluated. Due to the similarity of protein profiles of F. tularensis strains, a clear differentiation into subspecies could not be achieved. It is necessary to use other options for sample preparation, new generation devices with higher resolution, as well as apply additional approaches and analysis tools for successful subspecific differentiation.

The aim of the work was a comparative study of the expression of the main virulence genes in Vibrio cholerae strains of the classical biovar, typical and genetically modified strains of V. cholerae, El Tor biovar.

Materials and methods. Natural toxigenic strains of V. cholerae O1, classical biovar (J89, Pakistan, 1969), typical (M-887, Astrakhan, 1970) and genetically modified (301, Taganrog, 2011) strains of the El Tor biovar were used as model ones. The strains were grown under optimum conditions for the production of cholera toxin and toxin-coregulated pili. The assessment of strain growth was carried out in LB broth at room temperature with determination of the cells number on a Biowave DNA spectrophotometer (Biochrome Ltd., UK). Determination of gene expression was performed using real-time PCR with reverse transcription.

Results and discussion. The expression of structural (ctxA, tcpA) and regulatory (toxR, toxT, tcpP, tcpH) virulence genes has been investigated in V. cholerae strains of the classical biovar, typical and genetically modified strains of the El Tor biovar. Significant differences have been revealed in terms of time and level of maximum expression of these genes in strains of classical and El Tor biovars. It was found that ctxA and toxR genes expression in the genovariant strain reached its maximum 1–3 h earlier than in the other strains. At the same time, the level of ctxA gene expression corresponded to the level of the classical strain. The maximum expression of the toxR gene in the genovariant strain was higher than in typical El Tor and classical strains, and also had a clear inverse correlation with ctxA gene expression. Expression of the tcpA, toxT, and tcpH genes in the classical biovar strain reached its maximum 1–2 h earlier than in the El Tor biovar strains. These differences should be taken into account when conducting research work related to the study of the expression of the main virulence genes.

The aim of the study was to identify and compare potential determinants of aminoglycoside resistance in gentamicin susceptible Burkholderia pseudomallei strains.

Materials and methods. A bioinformatics analysis of whole genome shotgun sequences of three B. pseudomallei strains having different levels of sensitivity to gentamicin was carried out.

Results and discussion. B. pseudomallei is intrinsically resistant to aminoglycosides. Such strains, as a rule, are not taken into account in the classical scheme of isolation and identification. At the same time, there were no significant differences in the clinical manifestations of melioidosis during infection with gentamicin-resistant and sensitive strains. In B. pseudomallei strains of different sequence types (ST70, ST948, and ST1566), point missense mutations were found in the genes of three efflux pumps of the RND family: AmrAB-OprA, BpeAB-OprB, BpeEF-OprC, and one with unknown functions, as well as in the gene aminoglycoside-6’-N-acetyltransferase AAC(6’)-III. All three strains had amino acid substitutions in the AmrA periplasmic linker: ARG160SER, Arg116Gln and Gly237Arg, Thr317Lys, respectively. In moderately sensitive strains (ST948 and ST1566), an identical Val222Met substitution was found in the repressor of the AmrAB-OprA operon, AmrR. It is likely that the intermediate level of sensitivity to gentamicin in the studied strains is mediated by the constitutive expression of the AmrAB-OprA operon, which partially compensates for the structural defects. It is also possible that a dinucleotide deletion in the AAC (6’)-III aminoglycoside-6’-N-acetyltransferase gene, as well as detected mutations in the homologues of the periplasmic linker (BPSL2234) of an uncharacterized efflux operon of the RND family, are involved in the loss of resistance to gentamicin.

The aim of the work was to study the pathogenicity of newly emerging variants of SARS-CoV-2 on the model of the Syrian golden hamster.

Materials and methods. We used the strains of SARS-CoV-2 virus related to the VOC circulating in the territory of the Russian Federation. The experiments were carried out on outbreed Syrian hamsters obtained from the nursery of the SSC VB “Vector”. The infectious titer of coronavirus in tissue samples collected from infected laboratory animals was determined on a Vero E6 cell culture. The Ct in RT-PCR was considered an additional parameter for monitoring the viral load in the samples. The severity of lung tissue damage in Syrian hamsters with COVID-19 was assessed by histological preparations.

Results and discussion. 50 % infecting doses in case of the intranasal infection have been determined, histological analysis of lung tissues performed. The pathogenicity of various variants of the SARS-CoV-2 virus for the Syrian hamster has been evaluated, differences in infecting doses and pathological changes in the lungs have been revealed. SARS-CoV-2 viruses belonging to Beta genetic variant have the highest virulence, while Alpha variant has the lowest one when comparing the studied strains by the ID50 value. The Delta and Omicron variants have a matched ability to cause specific damage to the tissues of the respiratory tract, while being inferior only to the Beta variant. It has been demonstrated that Syrian hamsters are an adequate model for assessing the pathogenicity of the SARS-CoV-2 virus variants of concern. Variants of SARS-CoV-2 virus during intranasal infection has shown different degree of pathogenicity in the Syrian hamster model.

The aim of the study was to develop a set of primers and fluorescent probes for the detection of two chromosomal targets of Bacillus anthracis using real-time PCR based on the lambda_Ba03 prophage genes.

Materials and methods. BLAST analysis of B. anthracis chromosomal DNA identified two target genes in the region of lambdaBa03 prophage, BA_5358 (AE016879.1: 4852332..4853642) and BA_5361 (AE016879.1: 4855298..4856278). The designed primers and fluorescent hydrolysable TaqMan probes for simultaneous detection of B. anthracis chromosomal DNA by two stated genes were tested in qPCR for sensitivity and specificity.

Results and discussion. Studies performed on chromosomal DNA samples of closely related bacteria (B. cereus, B. thuringiensis, B. subtilis, B. clausii) have shown 100 % specificity of the developed sets of primers/probes. The sensitivity of the devised multiplex kit, tested on DNA samples of the m55-VNIIVViM vaccine strain and archival DNA samples of B. anthracis, reached 100 fg of bacterial DNA, which sets the limit of sensitivity at 17 genomes per reaction. The developed multiplex kit can be used as a separate tool for research laboratories studying anthrax.