Olga V. Duvanova

The aim of the work was to analyze the epidemiological situation on cholera in the world and in Russia and to make its forecast for 2026. Proactive epidemiological surveillance data showed that over the period of 2016–2025 there was an upward trend in cholera incidence worldwide: 5,474,013 cases were documented in 91 countries. The proportion of patients was distributed among countries as follows: Yemen (53.4 %), Afghanistan (11.7 %), Democratic Republic of the Congo (6.3 %), Nigeria (4.7 %), Somalia (3.2 %), South Sudan (2.5 %), Sudan (2.5 %), and Haiti (2.4 %). In 2025, 42 countries reported 589,571 cases and 8,140 deaths (5.1 % more than in 2024). The increase in cholera cases in 2025, compared to 2024, amounted to 5.12 %. Population migration remained the main risk-forming factor for the spread of cholera to different countries. In the Russian Federation, monitoring of labor migration was introduced with the organization of medical observation of arriving persons for seven days after arrival from cholera affected countries. As a result of monitoring surface water bodies in 2025, 50 non-toxigenic strains of Vibrio cholerae O1 circulating in the territory of the Russian Federation and belonging to different genetic lines were isolated. A decrease in the number of acute intestinal infections was noted from 13 (2024) to 5 (2025), caused by non-toxigenic V. cholerae nonO1/nonO139. Forecast for 2026: the risk of cholera importation persists due to the expected increase in the intensity of labor migration. Registration of acute intestinal infections and extra-intestinal infections caused by non-toxigenic strains of V. cholerae nonO1/nonO139 is probable. Detection of non-toxigenic strains of V. cholerae O1 and their clonal complexes circulating in water bodies will continue. Stable epidemiological situation on cholera in the Russian Federation is predicted for 2026.

Introduction. Vibrio cholerae motility plays a key role in the pathogenesis of cholera, so finding ways to suppress it is a promising approach to combating this infection. Objective: to study the effect of Fluorothiazinone on the motility of V. cholerae. Materials and methods. Flagellar motility was determined in 0.3% agar, with the motility zone measured, in 40 strains V. cholerae El Tor of varying epidemiological significance. The ability of these strains to acquire resistance to Fluorothiazinone was also assessed through repeated subcultures on alkaline agar containing Fluorothiazinone (100 mg/L). Results. A significant decrease in the motility of all studied cultures was observed in the presence of Fluorothiazinone, without the development of resistance. Conclusion. The dose-dependent ability of Fluorothiazinone to reduce the motility of V. cholerae was demonstrated for the first time.

The aim of the work was to conduct a comparative study of the composition of preparations made of outer membrane vesicles (OMV) of toxigenic and atoxigenic strains of Vibrio cholerae O1 El Tor and O139 serogroups. Materials and methods . The work used toxigenic and atoxigenic strains of V. cholerae O1 and O139 serogroups, from which OMV preparations were obtained. The structure of OMV preparations was investigated applying transmission electron microscopy. Genome-wide DNA sequencing was performed using the MiSeq and DNB-Seq-g50 platforms. The computer analysis of the obtained data was carried out using the SeqAnalayser 2.1 software. To conduct bioinformatic analysis, the following programs were used: Exonerate version 2.4.0 and SnapGene Viewer. Protein profiling was performed using MALDI-TOF mass spectrometry. The identification of antigenic determinants: cholera toxin and outer membrane proteins (OmpT, OmpU) was carried out by enzyme immunoassay (ELISA). Enzymatic activity was detected using appropriate media and substrates. Fatty acids were indicated through gas chromatography-mass spectrometry. Results and discussion . A comparative analysis of the composition of OMV preparations obtained from toxigenic and atoxigenic V. cholerae O1 and O139 strains has been carried out. The difference/similarity in the composition of OMV preparations has been revealed. According to the data of genome-wide sequencing and bioinformatics analysis, fragments of chromosomes containing a different set of genes and mobile genetic elements were found in OMV preparations obtained from strains with different genotypes. V. cholerae O1 and O139 OMV are able to participate in sorting and docking of cell contents, in vesiculation, contributing to the evolutionary transformations of the genome. OMV may be an additional factor in the pathogenicity/adaptation/persistence/competitiveness of the cholera pathogen.

Objective: to analyse the possibility of Vibrio cholerae survival in surface reservoirs of the Russian Federation subjects under conditions of low water temperature, compared to the temperature optimum for the growth and reproduction of these microorganisms in environmental objects (EO).Materials and methods: official data of the reference centre for cholera monitoring on the detection of Vibrio cholerae strains in the aquatic environmental objects of the Russian Federation subjects within the framework of monitoring studies for the period from 2019 to 2024 were used. Monitoring studies were organised and conducted in accordance with the current regulatory and methodological documentation. All isolated Vibrio cholerae strains were identified by regulated bacteriological, serological, molecular-biological methods.Results: 553 strains of Vibrio cholerae O1 serogroup (three of them toxigenic) and 13013 strains of NAG-vibrios were isolated for the period from 2019 to 2024. The range of minimum water temperatures of surface reservoirs from which the first strains of Vibrio cholerae were isolated in the administrative territories of types I–III on cholera epidemic manifestations was in the range from 1 °C to 15 °C, which is lower than the temperature optimum (above +16 °C) for their growth, and indicates the possibility of survival of these microorganisms in conditions of low temperatures of water bodies, and, therefore, does not exclude the possibility of spreading infection by water in the event of a toxigenic strain entering the reservoir.Conclusions: detection of NAG vibrios and non-toxigenic strains of Vibrio cholerae O1 serogroup in the water of surface reservoirs at temperatures up to 15 °C is an indicative sign of the existence of conditions conducive to the spread of infection in case of cholera importation into the territory of the Russian Federation and indicates the expediency of an earlier start and a later end of cholera monitoring studies in Russia.

The aim of the work was to analyze the peculiarities of the cholera epidemiological situation in the world and in Russia in 2024; forecast for 2025. The results of proactive epidemiological surveillance showed a continued upward trend in cholera morbidity in the world despite of the decrease in this indicator in 2024 (762 830 cases in 42 countries) as compared to 2023 (816 235 in 47 countries). A special feature was the import of a polyantibiotic-resistant Vibrio cholerae O1 El Tor strain from Tanzania to Island Mayotte. Active labor migration to the Russian Federation (RF) from countries with unfavorable cholera situation was noted (11 686 foreigners, 88.17 % – from India). No cholera patients (vibrio carriers) were identified in RF. The features of epidemiological situation have been established: two toxigenic V. cholerae O1 strains similar to the one isolated in 2023, and one toxigenic strain of NAG, documented in RF for the first time, were detected in surface water bodies. It has been determined that the non-toxigenic V. cholerae O1 strain, which caused a case of acute intestinal infection, and waterborne O1 strains circulating in Russia belong to the same clone. For the first time, the non-toxigenic V. cholerae O139 strain was isolated from a patient with acute intestinal infection. An increase in the number of non-toxigenic O1 strains isolated from water bodies was noted (335 in 2024, 52 in 2023), mainly due to the clonal complex (250 strains, Krasnodar Territory) spread through karst waters. Diseases caused by non-toxigenic NAG vibrios V. parahaemolyticus and V. fluvialis, were detected. The forecast for 2025 covers the risks of cholera importation, including cases caused by antibiotic-resistant strains; increase in labor migration from countries with an unfavorable cholera situation; the likelihood of detecting toxigenic O1 and nonO1/nonO139 strains in the environment, an increase in the number of acute intestinal infections caused by non-toxigenic cholera and other pathogenic vibrios; possible detection of extra-intestinal infections, an increase in the number of non-toxigenic V. cholerae O1 in environmental objects. It is advisable to start monitoring studies earlier (April) and finish them later (October) in RF in 2025 in type I territories classed according to epidemic manifestations of cholera.

Objective: retrospective analysis of the results of monitoring studies of environmental water bodies in Rostov-on-Don for the presence of V. cholerae for the period from 1989 to 2023 at stationary sampling points assigned to the Rostov-on-Don Anti-Plague Institute of Rospotrebnadzor, identification of trends and features of the dynamics of isolation and biological properties isolated strains. Materials and methods: in the period from 1989 to 2023, 4362 samples from aquatic ecosystems were examined. The organization and conduct of research was carried out in accordance with regulatory and methodological documents (SanPiN 3.3686-21, MUK 4.2.3745- 22, MUK 4.2.3746-22). Sequencing of isolated strains was performed on the MiSeq (Illumina) platform. Results: during the analyzed period, V. cholerae strains were found in all studied reservoirs of the Rostov-on-Don: in the Don, Temernik and Dead Donets rivers, mainly in July and August. Of the 122 isolated strains, 8 are epidemiologically significant (toxigenic strains) and 114 are nontoxigenic. The largest number of strains was isolated in 2022 — 21 strains. V. cholerae strains O1 (119 strains) and O139 (3) of serogroups, biovar classic and El Tor (Ogawa, Inaba and Gikoshima serovars) were found. Conclusions: epidemiological risks of the introduction of the cholerae pathogen from endemic countries, as well as from neighboring countries, in cases of complications of the epidemic of this infection, remain. In the surface reservoirs of the Rostov-on-Don, there are favorable conditions for the circulation of V. cholerae and the risk of spreading infection by water, in case of contamination by the cholerae pathogen of aquatic ecosystems.

The aim of the work was to study the composition of vesicle preparations (OMV) in Vibrio cholerae strains O1 El Tor (ctxAB^– tcpA^– ; ctxAB^– tcpA⁺ ) and O139 (ctxAB^– tcpA^– ) isolated from various sources. Materials and methods. V. cholerae strains O1 and O139 serogroups were used in the work, from which OMV preparations were obtained. The structure of OMV preparations was studied by transmission electron microscopy (TEM). Genome-wide DNA sequencing was performed on the MiSeq platform. The nucleotide and corresponding amino acid sequences of the genes were studied using bioinformatics analysis. Protein profiling was conducted using MALDI-TOF mass spectrometry. Enzymatic activities were detected using appropriate media and substrates. Determination of (surface determinants) lipopolysaccharide (LPS) and outer membrane proteins in the composition of OMV was carried out by enzyme immunoassay (ELISA). The analysis of the spectrum of fatty acids was performed by gas-liquid chromatography mass spectrometry. Results and discussion. OMV preparations have been obtained from non-toxigenic strains of cholera vibrios. TEM has revealed that OMVs are represented by spherical structures of about 40–200 nm. Genome-wide sequencing has shown that fragments of chromosomes containing genes of V. cholerae strains, O1 and O139 serogroups, from which they were isolated are present in the OMV. The bioinformatic analysis revealed differences in the structure of the ompT gene in the initial strains and in OMV obtained from V. cholerae strains O1 and O139 serogroups. The ΔompT gene of the OMV preparation from V. cholerae O139 serogroup was trunked and formed a peptide of 17 amino acid residues (-LENHHQKNREPDKEFPY-). Analysis of the OMV composition has revealed the presence of enzymes (N-acetyl-β-D-glucosaminidase and DNAazes), proteins of outer membranes (ompT and OmpU), LPS, saturated, сis/trans isomers of unsaturated fatty acids and branched fatty acids. Differences in the composition of OMV obtained from non-toxigenic strains of V. cholerae O1 and O139 serogroups have been identified.

The aim of the work was to study the structure of the alkyl sulfatase (asu) gene in Vibrio cholerae strains of various serogroups, as well as to compare nucleotide and amino acid sequences of alkyl sulfatases using various methods of bioinformatic analysis.Materials and methods. 483 strains of V. cholerae O1, O139 and nonO1/nonO139 serogroups were employed in the work. The search for the gene, its recurrence, and localization was carried out applying the Blast software. The nucleotide and corresponding amino acid sequences of the gene, as well as its structure, were studied using bioinformatic analysis. Sequencing was performed on the MiSeq (Illumina) platform. The enzymatic activity was detected using a medium, confirming the presence/absence of the gene by PCR in vitro and in silico.Results and discussion. Bioinformatic analysis of the nucleotide and corresponding amino acid sequences of the asu gene has been carried out and its structure investigated. Four functional domains have been identified. In the beta-lactamase domain, a conservative amino acid sequence -HAHADH- has been found in all strains of cholera vibrios, which is part of the Zn²⁺ binding motif. It has been established that the alkyl sulfatase of cholera vibrios belongs to the family of Zn²⁺-dependent β-lactamases. Blast analysis has revealed the similarity of nucleotide and amino acid sequences of alkyl sulfatases in representatives of V. cholerae O1 and O139 serogroups (ctxAB⁺tcpA⁺) and representatives of the genera Aeromonas and Pseudomonas, which is in the line with the data of 3D modeling of the amino acid sequence structures of the alkyl sulfatase enzyme in these microorganisms. The bioinformatic analysis of nucleotide and amino acid sequences of alkyl sulfatases in cholera vibrios has showed the conservativeness of these sequences in toxigenic strains and the presence of a number of single mutations in the asu gene in atoxigenic ones. The presence or absence of the asu gene has been established by PCR in vitro and in silico and confirmed by the results obtained using the Blast program. It is demonstrated that the presence/absence of the asu gene correlates with the ability/inability of O139 strains to hydrolyze SDS on the medium. These results can be used in studying mechanisms of cholera vibrios adaptation, persistence and pathogenicity.

Purpose: To evaluate the effectiveness and expediency of using vesicles of the outer membranes of atoxygenic strains of Vibrio cholerae O1 serogroup for the prevention of experimental cholera. Materials and methods: atoxigenic strains of V. cholerae O1 El Tor 18950 (ctxAB-tcpA-) and 18780 (ctxAB-tcpA+) isolated from the water of surface reservoirs were used to obtain vesicles. The protective properties of the obtained drugs were evaluated using a model of generalized cholera in white mice and a model of an isolated loop of the small intestine of an adult rabbit. Results: it has been shown that vesicles of the outer membranes isolated from atoxygenic strains of V. cholerae have a protective effect and prevent the development of infection in experimental animals when infected with a virulent strain of cholera. The obtained drugs are most effective when administered parenterally twice, with an interval of seven days, preventing the death of all white mice taken in the experiment and the development of pathogenetic processes in the small intestine of adult rabbits. Summary: the data obtained indicates the formation of pronounced immune protection against the disease in animals, as well as the possibility of using these structures to create preventive anti-cholera drugs.

Relevance. The process of production of outer membrane vesicles by bacteria is the main mechanism in intercellular communication and an intermediary in relationships of a very different nature (symbiosis, commensalism and parasitism), therefore, the study of the role of vesicles in the pathogenesis and immunogenesis of bacteria is an important and timely task.Aims. The purpose of this research was the analysis of scientific publications Russian and foreign journals for the period from 2002 to 2021 from the bibliographic databases of eLibrary.Ru, PubMed®, MEDLINE, dedicated to vesicles of outer membranes formed in various types of pathogenic and non-pathogenic bacteria.Conclusion. The study of the structure, factors of formation, functional significance of the mechanisms of action of bacterial vesicles, as well as the role of these structures in the pathogenesis and immunogenesis of various diseases, including especially dangerous ones, makes it possible to create new preventive drugs based on them. The use of vesicles as means of delivery of biological drugs and various antigens opens up new opportunities for improving the therapy and prevention of infections.