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The aim of the review was to analyze and assess the epidemiological situation on cholera in the world and Russia in 2013–2022 and to make a forecast for 2023. Over the period of 2013–2022, 500 administrative territories affected by cholera were identified in various regions of 71 countries of Asia, Africa and America (the Caribbean region) with formation of 69 endemic foci in 16, 41 and 12 countries, respectively. In 2022, 1 209 301 cases of cholera were registered in 36 countries of the world. The intensity of epidemic process in Asian countries (Syria, Lebanon) increased. Unfavorable epidemiological situation on the African continent persisted. Epidemics and large outbreaks, which began in 2021–2022 due to emergency situations (ES) of social and natural character, continued. The prediction of the stability of the epidemiological situation on cholera in the territories of constituent entities of the Russian Federation (RF), given for 2022, has been confirmed. In 2022, 43 non-toxigenic strains of Vibrio cholerae О1 were isolated from surface water bodies, 8 V. cholerae nonO1/nonO139 strains – from humans. Similarity of those strains with genetically closely related ones isolated in the course of monitoring in previous years in Russia, Donetsk People’s Republic (DPR) and Zaporozhye Region was demonstrated. In 2023, the risks of importation of the infection into RF are retained. It is associated with the intensification of epidemic processes in Asian, African and Caribbean region countries. The extended border with Ukraine, to where importation of cholera from endemic countries is possible, contributes to increased degree of threat. Bioterrorism is also not excluded. The consequences of a possible cholera epidemic complication in DPR, Lugansk People’s Republic, Zaporozhye and Kherson Regions are exacerbated by social emergencies resulting in disruption of infrastructure, interruptions in water supply, etc. In the absence of implementation of the risks of importation of this infection on the territory of RF, a stable epidemiological situation on cholera will be retained. Detection of non-toxigenic V. cholerae O1 strains (including probability of clonal complexes formation), as well as strains of non-O1/non-O139 serogroups, which can be etiological factors of sporadic cases or outbreaks of diarrheal diseases, in surface water bodies is predicted.

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 work was to summarize the results of cholera monitoring in 2021, to assess current trends in the development of the epidemic process, and to predict the epidemiological situation in the Russian Federation for 2022. It was established that within the period of 2012–2021, 4117264 cases of cholera with the spread of infection across 83 countries on all continents were registered in the world and there was a downward trend in the incidence in Asia and Africa. The dynamics of monthly morbidity in 2021 was associated with emergencies as factors of epidemiological risk. Epidemics and outbreaks of cholera were documented against the background of COVID-19 pandemic and laid a double burden on healthcare systems. At the same time, based on the overview of the results of cholera monitoring in the constituent entities of the Russian Federation, it was shown that the forecast of epidemic well-being given for 2021 was fully justified. It has been determined that the increase in the number of non-toxigenic strains of Vibrio cholerae O1 (67) isolated from water bodies compared to 2020 (25) is mainly due to the appurtenance of a number of isolates to clonal complexes. The study of phylogenetic relation has demonstrated that the detection of strains with genotypes which were previously identified in the isolates evidences the persistence potential. The identification of strains with new genotypes, which were earlier established in the strains circulating in other territories, pointed at the possibility of the occasional importations. The forecast of the epidemiological situation on cholera in Russia for 2022 is associated with the continuous existence of risks of introduction. If these epidemiological risks are not realized, a favorable epidemiological situation is predicted regarding this infection in the country. It is expected that the detection of epidemiologically insignificant strains of V. cholerae O1 in environmental water bodies, along with their clones and/or clonal complexes, will remain, including strains that may be an etiological factor in sporadic cases or outbreaks of disease.

The aim of the study was to analyze the resistance to antibacterial drugs of Vibrio cholerae strains isolated from environmental water bodies on the territory of Russia in 2019.V.cholerae O1 El Tor (14) and V.cholerae nonO1/nonO139 strains were used in this work. Sensitivity/resistance to 11 antibacterial drugs was determined using the method of serial dilutions in a solid nutrient medium. The presence of drug resistance genes was determined using real-time PCR. Fluctuations in sensitivity/resistance of V.cholerae were found in various years. The phenotypic resistance of the strains to tetracycline and trimethoprim/sulfamethoxazole correlated with the presence of the tetR and dfrA1 genes in them. The presence of ICE was not detected in V.cholerae strains containing the tetR and qnrVC1 genes. The variability and wide spectrum of V.cholerae resistance require close attention to the problem of antibiotic resistance of cholera. The detection of ICE in the studied V.cholerae strains, as well as antibiotic resistance genes not associated with ICE elements, emphasize the need for molecular genetic monitoring of V.cholerae antibiotic resistance.

Aim of the work – to assess the epidemiological situation on cholera in 2020 and to make a forecast for 2021 based on the monitoring data and analysis of morbidity around the world for the period of 2011–2020. During the period between 2011 and 2020, 4 413 988 cases of cholera were recorded in 97 countries of the world with a general trend towards a decrease in the incidence (coefficient of accuracy of approximation R2 – 0.5705). However, due to the continuing epidemic manifestations of cholera in the endemic countries of Asia, Africa and America, the epidemiological situation on cholera on these continents was characterized as unfavorable in 2020. The emergence of a new “post-Haitian” lineage was observed among epidemically hazardous strains of Vibrio cholerae O1. In 2020, no epidemically dangerous strains of V. cholerae O1, O139 were isolated from humans on the territory of the Russian Federation. 25 non-toxigenic V. cholerae O1 El Tor strains were isolated from environmental objects, eight out of which (ctxA-, tcpA+), according to PCR-INDEL typing and SNP analysis of sequences, belonged to the clonal complex. The results of the analysis of biological properties and phylogenetic relations between the isolated non-toxigenic strains provided the basis for considering the epidemiological situation on cholera in Russia in 2020 as a stable one and a similar forecast of its development in 2021. At the same time, the possibility of importation of this infection from endemic countries cannot be ruled out, as well as the need to carry out a complex of differentiated anti-epidemic (preventive) measures within the framework of the state sanitary-epidemiological surveillance in order to localize and eliminate the imported focus and avoid the spread of the infection.

Objective of the investigation was a comparative bioinformatics analysis of Vibrio cholerae О1 Cef (CHO cell elongating factor) genes and proteins. Materials and methods. 36 Vibrio cholerae О1 strains from the Rostov-on-Don Research Anti-Plague Institute collection have been utilized. DNA sequencing was conducted on the MiSeq platform (Illumina); gene identification and analysis was carried out by means of BioEdit 7.2.5, BLASTN 2.2.29, BLASTP, MEGA 7, Vector NTI Advance 11 software programs. Results and conclusions. The data obtained confirmed Cef to be rather conserved in choleragenic strains (carrying cholera toxin genes ctxAB as a part of genome-integrated CTX prophage): all of them shared closely related prototype alleles cefС or cefЕ1. The Е1 allele was also revealed in ctxAB– strains carrying the pre-CTX prophage and in a single strain lacking both prophages. In the rest of CTX–/pre-CTX– V. cholerae four novel cef variants, that were not previously described, have been identified, two of which (E2 and E3), belonging to the Russian isolates, appeared to be unique, while for the two others absolute homologues were found in NCBI. In this connection several strains which caused severe cholera-like diseases in humans were placed in the group of cefЕ4 host strains. Since Cef is one of pathogenicity/persistence factors of cholera vibrios, we presume that conservation of its altered variants in the course of natural selection embodies a certain biological sense in respect of possible acquisition of qualities, significant for realization of both pathogenic and persistence potential.

Carried out has been whole-genome sequencing of the Vibrio cholerae 81 El Tor Inaba strain DNA, isolated from Temernik River waters in the territory of Rostov-on-Don in July, 2014. Identified is the presence of hybrid CTX prophage, which contains ctxB gene of the classical type ( ctxB1 allele), as well as rstR gene El Tor type, tcpA gene with the mutations in coding and promoter regions ( tcpET CIRS allele), the null-mutation in rtxA gene, and extended deletion inside the pandemicity island VSP-II. All the stated above peculiarities are characteristic of cholera vibrio genovariants, which have an enhanced epidemic potential and have recently replaced the typical strains of this biovar.

Identified are the peculiarities of biological properties and origin of cholera vibrio O1 serogroup strains isolated from the Rostov-on-Don water bodies in the course of surveillance in 2008–2012. 41 atoxigenic V. cholerae O1 strains have been isolated from 767 water samples and investigated. Stable tendency of isolation of increased numbers of atoxigenic V. cholerae O1 strains over time has been demonstrated. In addition, in the strains under study detected have been the genes of additional pathogenicity factors, by PCR genotyping using specific primers for 45 nucleotide sequences associated with V. cholerae pathogenicity. The strains have also been classified according to 19 VNTR-genotypes grouped into 6 clusters based on VNTR-typing using exclusive copyright locus-specific primers. Discovered have been the strains with similar genotypes though isolated at different points both throughout the year and over the period of several years. These ones have probably been imported. They are characterized by a capacity to persist in ambient water bodies for a certain period of time.