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The aim of the study was to develop an algorithm for intraspecific differentiation of tularemia agent strains using a set of approaches based on amplification and sequencing technologies.Materials and methods. 97 strains of Francisella tularensis of various subspecies, biovars and subpopulations from the State Collection of Pathogenic Bacteria of the Russian Research Anti-Plague Institute “Microbe” were used in the work. The intraspecific identification of tularemia agent strains was carried out using the “F. tularensis-4c” system; analysis of the variability of the RD1 differentiation region, the sdhA gene, by applying the disk diffusion method using disks with erythromycin. Fragment Sanger sequencing was performed on a 3500 XL genetic analyzer (Applied Biosystems, USA) taking into account the manufacturer’s recommendations. Sequence homology assessment was conducted using the BLAST algorithm, the GenBank NCBI database, MEGA11 v11.0.13 and Unipro UGENE v50.0 software.Results and discussion. Subspecies- and biovarspecific mutations have been detected in the 23S rRNA gene. Promising regions of this gene for further investigation have been identified using fragment sequencing. A comprehensive scheme for intraspecific differentiation of tularemia microbe strains has been put forward, where at the first stage the subspecies and biovar japonica are determined, and at the second stage, the results are verified based on the determination of mutations in the 23S rRNA gene. The effectiveness of the proposed integrated approach has been confirmed in a study of 97 collection strains of tularemia agent. The conducted research allows for rapid identification of tularemia agent strains of different subspecies and verification of their taxonomic appurtenance using molecular-genetic methods, expanding data on the circulation of various subspecies, biovars and subpopulations of the pathogen in Europe, Asia and other regions of the world.

The aim of the study was to compare the nucleotide sequences of pgm‑region genes in Yersinia pestis strains isolated on the territory of the Caspian sandy and adjacent plague foci in 1925–2015. Materials and methods. 65 Y. pestis strains from the Caspian sandy and adjacent plague foci were used in the work. DNA isolation was performed using the PureLink Genomic DNA Mini Kit. Whole genome sequencing was conducted in Ion S5 XL System (Thermo Fischer Scientific). Data processing was carried out using Ion Torrent Suite software package 3.4.2 and NewblerGS Assembler 2.6. To compare the obtained sequences with the NCBI GenBank database, the Blast algorithm was used. The phylogenetic analysis was performed according to the data of whole genome SNP analysis based on 1183 identified SNPs. The search for marker SNPs was performed using the Snippy 4.6 program. The phylogenetic tree was constructed using the Maximum Likelihood algorithm, the GTR nucleotide substitution model. Results and discussion. The nucleotide sequences of pgm‑region genes of 65 Y. pestis strains from the Caspian sandy and adjacent plague foci have been assessed. Single nucleotide substitutions have been identified in Y. pestis strains from the Caspian sandy and Kobystan plain-foothill foci in the hmsR, astB, ybtS, ypo1944, ypo1943, ypo1936 genes, as well as a deletion of 5 bp in the ypo1945 gene, which is characteristic of strains of one of the phylogenetic lines of Y. pestis from the foci of Caucasus and Transcaucasia, isolated in 1968–2001. The data obtained can be used to differentiate Y. pestis strains from the Caspian sandy focus, as well as to establish the directions of microevolution of the plague pathogen in this region and adjacent foci.

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 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.

The aim was to evaluate the effectiveness of using the “Sterius 60” microwave disinfection system (Russia) for decontamination of objects infected with PBA of groups I–IV emerging as a result of working with infected laboratory animals.Materials and methods. Effectiveness verification of disinfection of biological waste generated as a result of the life of laboratory animals by SHF radiation was carried out in the microwave system “Sterius 60”, recommended by the manufacturer for disinfection of epidemiologically hazardous and extremely dangerous medical waste, including biological ones (classes B and C), by volumetric SHF heating. Carcasses of uninfected laboratory animals (white mice, Guinea pigs, suckling rabbits), granulated feed and bedding material (wood shavings), which are objects directly in contact with biomodels, were used as vivarium waste to be decontaminated. The following microorganisms were utilized as model test ones: Bacillus subtilus VKM B-911, Bacillus stearothermophilus VKM B-718, Bacillus licheniformis G VKM B-1711-D, Alcaligenes faecalis 415, Yersinia pestis EV, Bacillus anthracis STI. Laboratory utensils (plastic Petri dishes, porcelain mortars and pestles) were used as a mock-up chamber filler for model test microorganisms.Results and discussion. As a result of the study, data were obtained indicating that the microwave system for disinfection of medical waste “Sterius 60” is ineffective for decontamination of biological waste in laboratories working with biomodels infected with PBA of groups I–II. The established standard mode of disinfection of this system was effective only for non-spore forms of microorganisms, pathogenicity groups III–IV. Therefore, in our opinion, it is advisable to use it for decontamination of laboratory utensils infected with PBA of groups III–IV, directly at sites of waste generation.

The purpose of the study was to determine the effect of Yersinia pestis EV NIIEG on the process of neutrophil extracellular traps formation in vivo when modeling plague infection and assess their contribution to antiplague protection.Materials and methods. BALB/c mice, which were immunized subcutaneously with the Y. pestis EV NIIEG vaccine strain, were used in the study. Animals were infected with a virulent strain Y. pestis 231 at a dose of 20 LD50 (103 CFU). To evaluate the contribution of neutrophil extracellular traps (NETs) to antibacterial protection, an experimental model was used based on fermenting NETs in the abdominal cavity of mice with nuclease. To calculate the number of NETs in peritoneal exudate (PE) fluorescent microscopy was applied. Phagocytic activity of PE cells was determined by flow cytometry. Bactericidal effect of NETs was recorded using bacteriological method.Results and discussion. In pre-immunized mice, the process of NETs formation in response to the reintroduction of plague microbe living cells was 5 times more intense than in intact animals and was accompanied by a significant increase in the killing of Y. pestis cells in PE. The use of micrococcus nuclease in the experiment for fermentation of the NETs, produced in the body of immunized animals, provided evidence of NET participation in conferring anti-infective protection against plague infection. Thus, the established fact of the NET formation in case of Y. pestis infection of mice immunized with Y. pestis EV NIIEG vaccine strain and the influence of this process on the effectiveness of protection against plague is the basis for further clarifying the immunopathogenetic role of neutrophil granulocytes in plague.

Objective of the study was to select the standardized substrate containing dry hydrolysate of casein for preparation of nutrient medium utilized for manufacturing bivalent chemical cholera vaccine under submerged cultivation of cholera vibrio strains in fermenters. Materials and methods. We used Vibrio cholerae O1 strains of classical biovar: strain 569B Inaba and strain M-41 Ogawa. Examined were two dry substrates of the medium: enzymatic hydrolysate of casein, Type I Himedia (India) and pancreatic hydrolysate of casein, produced by the State Scientific Center of Applied Microbiology and Biotechnology (Russian Federation). Produced under laboratory conditions at the premises of the RusRAPI “Microbe” medium was used as a control. Submerged cultivation was conducted in bioreactors during (9±1) h with aeration and automatic feeding of glucose and ammonia. Production of protective antigens was measured applying immunochemical and biological methods. Results and discussion. It is demonstrated that submerged cultivation of cholera vibrio production strains on nutrient media under study provides for synthesis of protective antigens the parameters of which comply with the requirements of normative documentation. More standardized and higher indicator values of the target product are ensured by cultivation of producer strains on nutrient medium with a substrate from dry enzymatic hydrolysate of casein, containing (1.5±0.1) g/l of amino nitrogen for the strain V. cholerae M-41 and (2±0.1) g/l – for V. cholerae 569 B. Transition to the use of standardized dry protein components of cultivation media does not lower the quality of the chemical cholera vaccine, but allows for the reduction of cost price and duration of technological process.

Objective of this study was the molecular genetic characteristics of uropathogenic strains of Escherichia coli, isolated from urine of patients with urinary tract infections in Saratov City, in order to determine the phylogenetic groups and subgroups to which the strains belong, and to identify the genetic markers associated with virulence. Materials and methods. Molecular genetic characteristics of 102 strains of uropathogenic E. coli which were isolated from urine of patients with urinary tract infections, was performed. PCR was used to determine the frequency of oc-currence of genes (fimH, pap, sfa, afa, iha, irp2, iuc, iroN, hlyA, vat, usp, set-1, kpsMT, iss, cva, ompT) associated with factors of adhesion, iron intake, toxigenicity, resistance to action of serum (complement) and persistence, as well as belonging of studied strains to the specific phylogenetic groups and subgroups (by amplification of genes chuA,yjaA and TspE4.C2). Results and discussion. It was revealed that E. coli strains isolated from patients with urinary tract infections in Saratov city belonged to different phylogenetic groups and subgroups (A1, B1, B23, D3 и D2) and differed in their set of genes, which encode the basic virulence factors. At the same time, detection of uropathogenic E. coli which belong to the B23 subgroup was the most frequent. Moreover, the strains of this phylogenetic subgroup differed from others in the largest set of genes which encode virulence factors of the etiological agent. In all studied strains of uropathogenic E. coli which belong to different phylogenetic groups and subgroups the presence of genes responsible for the synthesis of siderophores (irp2, iuc, iroN), resistance and persistency (ompT) and adhesion factors (fimH, iha) was revealed. Therefore, strains of uropathogenic E. coli isolated from patients with urinary tract infections in Saratov city belong to different phylogenetic groups and subgroups and have a different set of genetic markers of virulence that can affect the degree of pathogenicity of the etiological agent, and the course of the disease.

Objective of the study was to construct the recombinant Y. pestis strain producing fluorescent protein GFP and analysis of the prospects of its usage for investigation of interaction of the agent with the protozoa, and also macroorganism of mammals (rodents). Materials and methods. To create the strain producing fluorescent protein GFP, we used the natural Y. pestis strain isolated in 2016 in Gorno-Altai high-mountain plague focus. Fluorescent protein gen was inserted into commercial vector pTurboGFP-B via electroporation. Properties of the obtained recombinant Y. pestis strain 367 pTurboGFP-B were studied using microbiological, biological, and molecular-genetic methods. Results and conclusions. The plague agent strain, containing vector plasmid pTurboGFP-B which encodes synthesis of green fluorescent protein GFP, and being resistant to ampicillin was constructed applying electroporation. The designed Y. pestis strain, producing green fluorescent protein, does not differ from the stock strain by its cultural-morphological, biochemical properties, virulence and survivability in mixed culture with Acanthamoeba castellani. On solid nutrient media, recombinant strain and its subcultures, obtained from infected animals, formed colonies of greenish-yellow color, becoming fluorescent under UV-light. In preparations from animals and from co-cultures with amoeba, fluorescent cells of plague agent were observed. The constructed strain can be utilized as a model one for investigation of interactions between plague agent and cells of protozoa (soil amoeba, nematodes) and mammals under laboratory conditions.

Objective of the study is to investigate phenotypic and molecular-genetic features and perform whole genome sequencing of Y. pestis strains isolated in Vietnam. Materials and methods. Studied were phenotypic and genotypic peculiarities of 20 plague agent strains isolated in different prefectures of Vietnam. Carried out was SNP-analysis of the strains, sequenced were genomes of 8 Y. pestis strains. Results and conclusions. Based on the results of studies of differential biochemical characteristics all the investigated strains were attributed to oriental biovar of the main subspecies of plague agent, which was confirmed by the presence of marker indel mutation – deletion of 93 bps in glpD gene. Investigated was also the plasmid composition of the strains. On the basis of the conducted genome sequencing and SNP-analysis appurtenance of 19 out of 20 strains under examination was determined. They belong to 1.ORI2v phylogenetic branch, relative to the strains isolated in Yunnan Province, China, which points to their common origin. Identified was a marker SNP and developed the method of SNP-typing for 1.ORI2v strains from Vietnam.

Various methods for evaluation of virulence properties of causative agents of infectious diseases in vitro were analyzed: molecular-genetic, cultural-biochemical, immunologic, physiologic. Predominant use of molecular-genetic methods, expediency of a complex approach, relevance of search of novel informative parameters of virulence are noted. Study of biological properties of pathogens in vitro is the first screening stage of evaluation of their virulence.

Objective of the study was to develop and then conduct medical trials of the “Monoclonal immune-enzyme test-system for the detection of plague agent (“EIAPESTF1-M”).Materials and methods. Utilized were materials for carrying out sandwich EIA. MCA 1B3 to Y. pestis F1 served as diagnostic immune-reagent. To determine sensitivity and specificity of the designed immune-enzyme test-system, investigated were samples of 24 natural and genetically modified pFra+ and pFra– Y. pestis strains and 56 strains of heterologous bacteria Enterobacteriaceae family.Results and conclusions. Based on monoclonal antibodies to Yersinia pestis capsular antigen, constructed was “Monoclonal immune-enzyme test-system for the detection of plague agent (“EIAPESTF1-M”), which is characterized by high specificity and allows for the detection of encapsulated plague agent strains in biological samples and for identification of pure cultures with sensitivity of 5·105 – 1·106 mc/ml. It is highly competitive with comparator drug – “Diagnostic fluorescent absorbed equine plague immunoglobulins”, lyophilizate for diagnostic purposes, by RusRAPI “Microbe”. It possesses such advantages as objective result recording and capability of result documentation. “EIAPESTF1-M” is registered in the RF Federal Service for Surveillance in the Sphere of Healthcare and Social Development, reference No 2013/711, dated 31.05.2013 and approved for use in the territory of the Russian Federation.

Put forward are two alternatives of a new method for optimization of conditions of LPS obtaining and purification from Y. pestis strains; as well as for avoiding application of poisonous and hard-to-remove reagents; for simplification and cost-cutting of the technique; and for rationalization of production waste management. This method involves preliminary salt-water extraction of bacteria, for elimination of easy-dissolving substances, with the subsequent fracturing using ultrasound in lysing buffer (0,1 M Tris-HCl, pH 8,0; 10 mmol of EDTA, 1 % Triton X-100). The first alternative for deproteinization of non-purified endotoxin is the commercial preparation of proteinase K (Sigma), the second one - an enzyme complex - proteovibrin, isolated from waste material accumulated in the process of cholera chemical bivalent vaccine production. Apart from this, introduced has been a phase of sample acidification by applying glacial acetic acid up to pH 3,2-3,4 to decontaminate LPS from nucleic acids. These two variations of the method provide for enhancement of LPS preparation quality as compared to prototype method, and for obtainment of plague agent endotoxin that is hardly distinguishable in physical-chemical properties, homogeneity, immunochemical activity and specificity from the antigen, manufactured by means of water-phenol extraction following Westphal O. technique.

Objective of this review is to analyze diachronically paradigm shift as regards problems of specific plague prophylaxis and appreciate contribution of the present-day scientific discoveries in the sphere of plague agent investigations and peculiarities of its interaction with host organism to the solution of topical issues of vaccine development that will be safe and tangibly effective against this particularly dangerous disease. Outlined is the historical background of the conceptual evolution concerning specific plague prophylaxis and events that are landmarked with eminent scientific discoveries by A.Yersin, French researcher and microbiologist. Given are the data on the current state of plague immune-prophylaxis both in Russia and around the world. Through the prism of the latest researches that assume application of advanced technological resource of medical sciences (molecular biology, biotechnology, bioinformatics, molecular immunology) put forward is the prospective of search and construction of safe and effective anti-plague next generation vaccines.

mc/ml. Additionally, this test-system has been proving for acquisition of sustainable results after 6 months of storing (the observation period). Medical trials of the panel of reagents “Monoclonal dot-immuno-enzyme test-system for tularemia microbe detection” have shown it to be a prospective preparation for implementation into the national healthcare practices both under stationary and field conditions.

Designed is immuno-enzyme test-system for the detection of antibodies to Yersinia pestis capsular antigen F1 – “ELISA-Ab-F1 Yersinia pestis”. On the model of laboratory mice it is demonstrated that this test-system is highly specific, its diagnostic titer being 1/320.Diagnostic value of the test-system is 83.3–88.9 % as revealed through investigations of sera and blood suspension samples, swabs of thoracic organs of animals, inoculated with live plague vaccine, strains of plague microbe, containing and deprived of pFra, as well as with heterologous bacteria.

, and degraded polysaccharide (PS) are easily soluble in water and in 0,9 % NaCl solution. They are homogenous and characterized by an adequate degree of purity. Aside from that, it is demonstrated that potentially PS is the most productive molecule fragment of LPS for the construction of plague immunodiagnostic preparation, since despite its decreased cytotoxocity PS retains identity of chemical composition and immunechemical specificity of endotoxin.

Presented is the survey of the national and foreign literature concerning the questions of improvement of cholera immunodiagnostics. Considered are the problems and prospects of development of different preparations designed for cholera vibrios detection and serologic diagnostics of the disease.

Carried out was comprehensive immunochemical and immunobiological analysis of plague microbe species-specific capsule F1 protein, and glycoproteid main somatic antigen (MSA) the latter being common in specificity in closely related plague and pseudotuberculosis agents. Both preparations isolated from Yersinia pestis cells using standard techniques were examined in the test of accelerated ageing (exposure at 37 °C for 4 weeks) and in stress conditions (exposure at 60 °C for 24 hours). They were shown to preserve their main features that characterized their authenticity and specific activity (visual appearance, solubility, chemical content, immunochemical homogeneity and immunobiological activity) as compared with preparations stored in refrigerator at 4-8 °C.

This review is devoted to the analysis of the main achievements of the Russian and foreign scientists in the sphere of development of immunodiagnostic methods for detection of Francisella tularensis and specific serum antibodies. The most important problems concerning perspectives of constructing of the modern effective test-systems for tularemia immunodiagnostics are discussed.

Analysis of the recent domestic and foreign publications concerning the problems of anthrax immunodiagnosis is presented in the current review. The major achievements in the development of the procedures to detect Bacillus anthracis and its antigens using various immunodiagnostic assays are briefly characterized. The most important problems are discussed in connection with the efforts to increase the efficacy of the modern immunodiagnostic kits and their introduction into practice.