Cholerae El Tor Strains Research Articles

Analysis of changes in the genome of Vibrio cholerae O1 El Tor genovariants during the current period of the cholera pandemic

Introduction. The genome variability of genetic variants of El Tor cholera agent has led to the emergence of strains carrying mutations in various genes associated with epidemically important pathogen properties. This situation requires an assessment of the trends in these changes in order to predict the pathogenic potential of previously unknown variants and promptly develop new tools for their diagnostics and prevention.
 The purpose of this work was to analyze the dynamic changes in pathogenicity and drug resistance genes of V. cholerae El Tor genetic variants from endemic countries and Russia.
 Materials and methods. We analyzed complete genome nucleotide sequences of 104 V. cholerae El Tor strains from the NCBI Gen Bank and European Nucleotide Archive databases, as well as those obtained by us. The nucleotide sequences were analyzed using the UGEN v. 45.1 software. The dendrogram was constructed using maximum parsimony algorithm in BioNumerics v.7.6 software package based on the multiple alignment generated using the Snippy 4.6.0 program.
 Results. Genomic sequences of 103 strain genovariants isolated on the territory of nine endemic countries of Asia and Africa, as well as in Russia in 1991-2022, have been compared. It is shown that the process of genovariant genome changing was multistage and occurred due to the continuous accumulation of point mutations in key (ctxB and tcpA) and additional (rtxA) genes of pathogenicity and core genes of antibiotic resistance (gyrA, parC and carR), as well as a deletion in SXT element. The most important was the change in the ctxB gene and the emergence of new genovariants with the ctxB7 allele, which replaced the previously prevalent strains. Analysis of altered genome regions of 83 strains from endemic regions has revealed eight genotypes, while the strains (21 isolates) imported to Russia belonged to only five of them including highly virulent strains with the ctxB7 allele and lost PolR biovar-specific feature due to carR gene mutation. The established close phylogenetic relatedness of genovariants from Russia with strains from endemic Asian countries confirms their importation from this region.
 Conclusion. The sequential occurrence and accumulation of mutations in the pathogenicity and drug resistance genes in the genome of genovariants in endemic regions have been shown, which leads to a change in their epidemically important features. The importation of new highly virulent genovariants into Russia has been established, which indicates the need for an ongoing assessment of changes in the genome of this pathogen for the timely development of adequate means of gene diagnostics and prevention.

Two defence systems eliminate plasmids from seventh pandemic Vibrio cholerae.

Horizontal gene transfer can trigger rapid shifts in bacterial evolution. Driven by a variety of mobile genetic elements-in particular bacteriophages and plasmids-the ability to share genes within and across species underpins the exceptional adaptability of bacteria. Nevertheless, invasive mobile genetic elements can also present grave risks to the host; bacteria have therefore evolved a vast array of defences against these elements1. Here we identify two plasmid defence systems conserved in the Vibrio cholerae El Tor strains responsible for the ongoing seventh cholera pandemic2-4. These systems, termed DdmABC and DdmDE, are encoded on two major pathogenicity islands that are a hallmark of current pandemic strains. We show that the modules cooperate to rapidly eliminate small multicopy plasmids by degradation. Moreover, the DdmABC system is widespread and can defend against bacteriophage infection by triggering cell suicide (abortive infection, or Abi). Notably, we go on to show that, through an Abi-like mechanism, DdmABC increases the burden of large low-copy-number conjugative plasmids, including a broad-host IncC multidrug resistance plasmid, which creates a fitness disadvantage that counterselects against plasmid-carrying cells. Our results answer the long-standing question of why plasmids, although abundant in environmental strains, are rare in pandemic strains; have implications for understanding the dissemination of antibiotic resistance plasmids; and provide insights into how the interplay between two defence systems has shapedthe evolution of the most successful lineage of pandemic V. cholerae.

Features of the Biological Properties of <em>Vibrio cholerae</em> Isolated during the Monitoring of Water Bodies in Rostov-on-Don from 1989 to 2018

The goal is to study the features of the biological properties of Vibrio cholerae strains found in environmental objects (EO) on the territory of Rostov-on-Don from 1989 to 2018.Materials and methods. Bacteriological, molecular biological and statistical methods were used to study 73 strains of cholera vibrios O1, O139 and 1702 strains of nonO1/nonO139 serogroups isolated over a 30-year period.Results and discussion. It was found that in Rostovon-Don, 78.0 % of toxigenic strains were isolated from all isolated from environmental protection in Russia, among which 2 were genetically unchanged. The V. cholerae O1 classical strain and 72 V. cholerae El Tor strains were found, of which 70 % belonged to the Ogawa serovar, and 3 % of the nontoxigenic strains were susceptible to the classical phage. A “very weak direct relationship” was statistically revealed between the isolation of V. cholerae O1, O139 and V. cholerae nonO1/nonO139 strains, in which the dominant serogroups (O67, O76, O75, O53, O16) were identified, and 18 % of the strains showed atypical agglutinability. Revealing the biological characteristics of V. cholerae strains contributes to the optimization of monitoring studies.

Isolation of Vibrio cholerae from clinical and drinking water samples during Cholera Outbreak in Khairpur Sindh Pakistan

Background: Cholera is a diarrheal disease that is caused by the bacterium Vibrio cholerae that transmits through contaminated water, food, oral-fecal route and spread through poor sanitation system. This study aims to investigate the reports of clinical and drinking water samples during an epidemic in Pakistan.
 Methodology: This study was conducted in District Khairpur including 660 samples (360 from clinical and 300 from drinking water) from 2014-2016. All samples were enriched in Alkaline peptone water for 6 hours and then streaked on TCBS agar, incubated at 35ºC for 24 hours. The next day standard microbiological, biochemical, serological techniques were used for the identification of V. cholerae and further identification was performed using PCR.
 Results: Out of 360 clinical samples, 76(21.11%) were positive for V. cholerae. The species-specific Outer membrane protein W precursor (ompW) gene was amplified and shown at the correct size (588 bp) through agarose gel electrophoresis. The serotyping revealed that the isolates belonged to serogroup Inaba, O1. cholerae O1 strains shown typical El Tor phenotype similar to V. cholerae El Tor strain N16961 (PBR VP+) used as the reference strain in this study. All age groups were affected where the highest onset was seen among those aged 19 years and above. The culture of drinking water (n=300), observed negative on TCBS agar.
 Conclusion: As far as our knowledge, this is the first time when the presence of V. cholerae El Tor peak has been reported for causing cholera outbreaks in Khairpur Sindh, Pakistan. However, these findings can be used for further investigations and recognizing control measures.

Heterogeneity by antibiotic sensitivity and genotype of Vibrio Cholerae El Tor strains isolated from environmental objects in Russia

BACKGROUND: Waterborne diseases kill 3.4 million people worldwide each year. Cholera is one such disease. Up to 4 million cases of this infection occur in the world every year, leading to more than 100,000 deaths. The plasticity of the genome of the causative agent of cholera, the mobility of genetic elements carrying factors of pathogenicity and antibiotic resistance, contribute to the variability and unpredictability of the spectrum of resistance, the formation of new pheno- and genotypes. A single Vibrio cholerae isolate can contain up to 40 different genes that can confer resistance to 22 antibiotics, representing nine different classes of antimicrobial drugs. The ability of Vibrio cholerae to long-term survival in aquatic ecosystems in which there is an active exchange of genetic information and new ecological lines may arise that have potential advantages in the adaptation of microorganisms to adverse conditions, emphasizes the complexity of the ways of transmission of this infection and the need for studies at the environmental level. Periodic deliveries of cholera to the territory of the Russian Federation with (without) the spread of the infectious agent, V. cholerae contamination of surface water bodies used as sources of water supply and for recreational water use, the possibility of implementing the main route for cholera (water) the pathway for the spread of the pathogen of the infection indicate the need for conducting annual monitoring of antimicrobial resistance as part of the epidemiological surveillance of cholera in order to obtain information on the distribution, nature and dynamics of resistance in a specific period of time in a given territory.
 AIM: Analysis of the spectrum of antibiotic resistance of Vibrio cholerae O1 serogroup strains isolated from environmental objects in various territories of the Russian Federation in 2020.
 MATERIALS AND METHODS: 25 strains V. cholerae О1 El Tor, isolated from environmental objects in the Russian Federation in 2020. The sensitivity / resistance of the studied strains to 13 antibacterial drugs was determined by the method of serial dilutions on a solid nutrient medium in accordance with guidelines. PCR-genotyping of strains V. cholerae El Tor was performed for 14 target genes, followed by cluster analysis.
 RESULTS: The strains showed resistance markers to furazolidone, trimethoprim/sulfamethoxazole, ampicillin, nalidixic acid, ceftriaxone, which formed 5 phenotypes. PCR-genotyping genotyping of 14 target genes divided the strains into five genotypes (A1A5), corresponding to certain territories. The antibiotic resistance profiles within the same genotype in V. cholerae О1 El Tor belonging to different territories were both the same and different.
 CONCLUSION: The genotypic diversity of isolated strains was revealed, the variability of resistance markers even in one region, which indicates both changes in the V. cholerae population and the possibility of circulation of various geno- and phenotypes, which emphasizes the importance of constant monitoring of these pathogens.

Antibiotic resistance in Vibrio cholerae El Tor strains isolated during cholera complications in Siberia and the Far East of Russia

Currently, the spread of antimicrobial resistance (AMR) is a global trend and poses a severe threat to public health. The causative agent of cholera, a severe infectious disease with pandemic expansion, becomes more and more resistant to a wider range of drugs with every coming year. The Vibrio cholerae genome is highly flexible and adaptive; the acquisition of the SXT mobile element with a cluster of antibiotic resistance genes on it has marked a new stage in the adaptive evolution of the pathogen. The territory of Siberia and the Russian Far East is free of cholera; however, in the 1970s and 1990s a number of infection importation cases and acute outbreaks associated with the cholera importation were reported. The aim of this study was to describe the phenotypic characteristics and genetic determinants of AMR in V. cholerae strains isolated during epidemic complications in Siberia and the Far East of Russia, as well as to clarify the origin of the strains. The present research comprises analysis of nine V. cholerae El Tor strains isolated from patients and water sources during epidemic complications in Siberia and the Russian Far East in the 1990s. Here, we compared the phenotypic manifestations of antibiotic resistance among strains, harbored the resistance patterns in genomes; we also determined the structure, the type of SXT elements, and the mobilome profile based on the accepted classification. We identified that strains that caused outbreaks in Vladivostok and Yuzhno-Sakhalinsk in 1999 had ICEVchCHN4210 type SXT element with deletion of some loci. The research shows that the integration of the genome, SNP and the mobilome, associated with antibiotic resistance, analyses is necessary to understand the cholera epidemiology, it also helps to establish the origin of strains. The study of resistance determinants features allowed to make a conclusion about the heterogeneity of V. cholerae strains that were isolated during outbreaks in Vladivostok and Yuzhno-Sakhalinsk in 1999.

Comparative analysis of adaptation properties in typical and genetically altered Vibrio cholerae El Tor strains

Aim. Study of biological properties in natural strains of genovariants of V. cholerae biovar El Tor, affecting their adaptation capacities under nutrient deficiency while comparing them with typical strains. Materials and methods. Competitive sampling was carried out through plating a mixture of cells of the two strains under investigation into autoclaved river water. Growth rate was evaluated through the optic density values. Gene expression was studied applying RT-PCR with designed primers and probes. Results. It is established that during combined cultivation of V. cholerae El Tor typical strains and genovariants under the shortage of nutrient substances (autoclaved river water), at room temperature, the level of survivability in genetically altered strains is higher than in typical strains, which points to their expressed adaptation advantages over the typical ones under the stated conditions. It is demonstrated that selective benefits of genovariant strains are provided by higher cell growth rate and increased rpoS gene expression. Conclusion. Obtained have been new data on the ability of bacterial strains of V. cholerae El Tor genovariants to rapidly grow and better express global regulator of stress response, rpoS gene, which, probably, contributes to their enhanced adaptation not only under nutrient deficiency, but under the influence of other stress factors too.

VIBRIO CHOLERAE EL TOR ANTIBIOTIC RESISTANCE GATHERED FROM ENVIRONMENTAL OBJECTS ON THE TERRITORY OF THE RUSSIAN FEDERATION

The paper presents the analysis of Vibrio cholerae El Tor strains antibiotic resistance gathered from environmental objects on the territory of the Russian Federation during 2007–2016. We determined the sensitivity of 268 strains of V. cholerae El Tor to 12 antibacterial drugs by the method of serial dilutions in a dense nutrient medium. The strains showed resistance to 1–7 antibacterial drugs. The emergence of quinolone resistance in polyresistant strains of V. cholerae E.

Comparative genomics of Vibrio cholerae El Tor strains isolated at epidemic complications in Siberia and at the Far East

The territory of Siberia and the Far East of Russia is classified as epidemically safe for cholera; however, in the 1970s and 1990s a number of infection importation cases and acute outbreaks associated with the cholera importation were reported. Here, we analyze genomes of four Vibrio cholerae El Tor strains isolated from humans during epidemic complications (imported cases, an outbreak) in the 1990s. The analyzed strains harbor the classical allele of the cholera toxin subunit B gene (ctxB1); thus, belong to genetically altered variants of the El Tor biotype. Analysis of the genomes revealed their high homology with the V. cholerae N16961 reference strain: 85–93 SNPs were identified in the core genome as compared to the reference. The determined features of SNPs in the CTX prophage made it possible to propose the presence of a new subtype – CTX-2a in two strains; the other two strains carried the prophage of CTX-3 type. Results of phylogenetic analysis based on SNP-typing demonstrated that two strains belonged to the second wave, and two – to the early third wave of cholera dissemination in the world. Phylogenetic reconstruction in combination with epidemiological data permitted to trace the origin of the strains and the way of their importation to the Russian Federation directly or through temporary cholera foci.

A. LECTINS IN THE IMPLEMENTATION OF ANTI-LACTOFERRIN ACTIVITY OF VIBRIO CHOLERAE

Anti-lactoferrin activity (AlfA) is one of the factors contributing to the persistence of V. cholerae in human body in formation of human vibriocarriers. It is shown that in the AlfA mechanism cholera vibrio lectins are participating as an initial link specifically binding to lactoferrin at the surface of microbial cells, providing for subsequent cleavage of this protein with the help of V. cholerae exoproteases. Lectins are proteins or glycoproteins of non-immune class, capable to reversibly bind to the carbohydrate fraction of glycoconjugates without breaking the covalent structure of any of the recognizable glycosyl ligands. As glycoproteins, lectins ensure the complementary highly specific carbohydrate-protein binding of the active sites of target cells (namely lactoferrin). It is proved that all V. cholerae El Tor and Bengal strains possess hexose-specific lectin receptors (especially mannose). Atoxigenic V. cholerae O1 and O139 strains possess, in addition to hexose receptors, lectins specific to aminosugars.

Resistance to high temperatures salmonellosis circulating in Kemerovo region

Anti-lactoferrin activity (AlfA) is one of the factors contributing to the persistence of V. cholerae in human body in formation of human vibriocarriers. It is shown that in the AlfA mechanism cholera vibrio lectins are participating as an initial link specifically binding to lactoferrin at the surface of microbial cells, providing for subsequent cleavage of this protein with the help of V. cholerae exoproteases. Lectins are proteins or glycoproteins of non-immune class, capable to reversibly bind to the carbohydrate fraction of glycoconjugates without breaking the covalent structure of any of the recognizable glycosyl ligands. As glycoproteins, lectins ensure the complementary highly specific carbohydrate-protein binding of the active sites of target cells (namely lactoferrin). It is proved that all V. cholerae El Tor and Bengal strains possess hexose-specific lectin receptors (especially mannose). Atoxigenic V. cholerae O1 and O139 strains possess, in addition to hexose receptors, lectins specific to aminosugars.

ANTIBIOTIC RESISTANCE OF VIBRIO CHOLERAE O1 EL TOR ISOLATED ON THE TERRITORY OF THE RUSSIAN FEDERATION IN 2006-2015

Aim of the study. The analysis of antibiotic resistance and molecular mechanisms of the persistence of Vibrio cholerae О1 El Tor strains, isolated from patients and environmental objects on the territory of the Russian Federation in 2006-2015. Material and Methods. The susceptibility of 34 V. cholerae El Tor strains to 13 antibacterial drugs was determined by the method of serial dilutions in a rich culture medium (Instructional Guidelines (МUК) 4.2.2495-09). Results. The strains showed resistance to 1-5 antibiotics (levomicetin, streptomycin, nalidixic acid, furazolidone, trimethoprim/sulfamethoxazole) and harbored SXT-element with antibiotic resistance genes. The emergence of quinolone resistance in V. cholerae O1 El Tor strains with accompanying multiple drug resistance limits the choice for drugs for etiotropic therapy and aggravates the possibility of unfavourable cholera outcome.

Холерные вибрионы неО1/неО139 серогрупп в этиологии острых кишечных инфекций: современная ситуация в России и в мире

Cholera vibrios of nonO1/nonO139 serogroups (NAG vibrios) are well known as natural inhabitants of aquatic environments and as agents of acute intestinal infections (AII) with different degree of severity. On the background of the current vehement dissemination of the new highly virulent Vibrio cholerae El Tor strains, the moral and economic damage from NAG vibrios is not that evident, but still, not less real and rather significant. In spite of rare association with large outbreaks, NAG vibrios rank in the etiology of AII all over the world and pose a potential threat for the population health in our country. The paper reviews the present-day morbidity as regards NAG infections in various countries, including Russia; as well as the molecular premises of the agents’ pathogenicity and drug resistance. Analysis of the published data has revealed an utter heterogeneity of NAG populations, circulating in certain territories, by reference to the presence/absence of genetic determinants of pathogenicity, persistence, housekeeping and antibiotic resistance factors. Nevertheless, the joint gene-pool of the population includes rather a wide set of genes and can expand due to importations of strains, which differ from resident ones in the genotypes, from other regions. This brings about the danger of emergence of clones with higher pathogenic and, probably, even epidemic potential driven by gene exchange, and the consequences of their occurrence are unpredictable. Therefore, the NAG vibrios demand proper attention from investigators and sanitary-epidemiological institutions of the Russian Federation.

Structural-Functional Analysis of the Genes, Encoding Biosynthesis of Mannose-Sensitive Hemagglutinating Pili of Adhesion in Different Vibrio cholerae El Tor Strains

Objective of the study is to conduct comparative structural and functional analysis of the genes, encoding biosynthesis of man-nose-sensitive hemagglutinating pili in typical V. cholerae El Tor strains and genovariants. Materials and methods. Utilized were typical and genetically altered strains of cholera vibrio, biovar El Tor, isolated in the territory of the Russian Federation between 1970 and 2012 from ambient environment objects and from patients. Applied were microbiological and molecular-genetic methods, as well as analysis of the data on the whole genome sequencing. Results and conclusions. Using PCR assay the presence of mshA gene, encoding basic sub-unit of MSHA pili, has been detected in all of the tested strains. Comparative analysis of the nucleotide sequence of the genes, included into msh cluster, has revealed identity of the nucleotide sequence of mshA gene, both in typical V. cholerae strains and genovariants. Thereat, in strains of genovariants, isolated at the time of their emergence (1988, 1993, 1994), the structure of the other genes in msh operon is identical to typical El Tor vibrios. At the same time, since 1997, in strains of V. cholerae El Tor genovariants, in the sequence of the genes, involved in the assembly and secretion of MSHA pili, identified have been the SNPs, which do not influence biosynthesis of these pili, but their occurrence, probably, was due to adaptation of the genovariant strains to varying living conditions.

The Cpx system regulates virulence gene expression in Vibrio cholerae.

Bacteria possess signal transduction pathways capable of sensing and responding to a wide variety of signals. The Cpx envelope stress response, composed of the sensor histidine kinase CpxA and the response regulator CpxR, senses and mediates adaptation to insults to the bacterial envelope. The Cpx response has been implicated in the regulation of a number of envelope-localized virulence determinants across bacterial species. Here, we show that activation of the Cpx pathway in Vibrio cholerae El Tor strain C6706 leads to a decrease in expression of the major virulence factors in this organism, cholera toxin (CT) and the toxin-coregulated pilus (TCP). Our results indicate that this occurs through the repression of production of the ToxT regulator and an additional upstream transcription factor, TcpP. The effect of the Cpx response on CT and TCP expression is mostly abrogated in a cyclic AMP receptor protein (CRP) mutant, although expression of the crp gene is unaltered. Since TcpP production is controlled by CRP, our data suggest a model whereby the Cpx response affects CRP function, which leads to diminished TcpP, ToxT, CT, and TCP production.

Whole-Genome Sequencing of a Vibrio cholerae El Tor Strain Isolated in the Imported Cholera Focus in Siberia.

The draft genome sequence of Vibrio cholerae O1 strain I-1263, isolated from a patient in the imported focus in Siberia, was determined. The established structural features of the mobile genetic elements indicate stage-by-stage formation of a highly pathogenic V. cholerae clone and promote understanding of the mechanisms of evolutionary pathogen transformations.

Epidemiological Surveillance of Cholera in Russia During the Period of the Seventh Pandemic

In this work basic stages of formation of the epidemiological surveillance of cholera in Russia are described. In 1990-s for the first time zoning by epidemic manifestations of cholera was carried out at the level of subjects forming parts of Russia and other Republics of the Soviet Union with the introduction of differential tactics of epidemiological surveillance. Improvement of epidemiological surveillance of cholera was aimed at harmonization with the IHR (2005), integration of epidemiological surveillance of cholera and social-hygienic monitoring of water objects of I and II categories. Characterization of isolated Vibrio cholerae strains (1990-2014) on the genomic basis determined the emergence of new VNTR-genotypes of V. cholerae O1 ctxAB+ tcpA+, responsible for outbreaks, simultaneously with isolation of V. cholerae 01 ctxAB-tcpA-strains during monitoring of environmental objectsfor cholera. A viewpoint is considered of the beginning of the eighth cholera pandemic in the context of emergence of V. cholerae El Tor strains with CTXφ prophage carrying ctxB gene of cholera toxin of classical biovar. Main directions offurther enhancement ofepidemiological surveillance include the study of basic data structures used in the epidemiological surveillance system, the use of zoning of municipal units offederal subjects with corresponding surveillance tactics and expected economic effect.

A retrospective macrorestrictive analysis of Vibrio cholerae eltor strains isolated under epidemic complications in the Russian Far East

A retrospective study of the clonal structure of 24 Vibrio cholerae eltor strains isolated during epidemic complications in the Russian Far East was carried out on the basis of a macrorestrictive analysis of Vibrio cholerae eltor genomic DNA using NotI and SfiI endonucleases. It was found that clonal (by amplification profiling data) toxigenic strains (n = 23) were characterized by variability of the NotI/SfiI-generated restriction profiles. The V. cholerae eltor isolated during an outbreak in the city of Yuzhno-Sakhalinsk were differentiated into four pulse types, with one dominating type detected in 76.5% of the strains. A separate NotI/SfiI-restriction profile was characteristic for the isolates from Primorskii krai. A nontoxigenic strain formed a separate dendrogram line from the toxigenic strains on the basis of the PFGE-pattern structure. The use of macrorestriction analysis was shown to be effective for deep characterization of the V. cholerae population structure and for ascertainment of molecular-epidemiological regularities in the territorial distribution of certain V. cholerae clones.

Model of Vibrio cholerae biofilm as a mechanism of its survival in surface water reservoirs

Vibrio cholerae eltor strains with different epidemic importance isolated from river water in the city of Vladivostok during a cholera outbreak (1999) and in the city of Irkutsk during a safe cholera period (2005) are used in the experiment. A biofilm structure consisting of a peripheral part, bundles, polysaccharide matrix, canals, and polymorphic vibrios is presented by light and luminescent microscopy. The metachromatic pink coloring of the matrix (crystal violet and toluidine blue) or fluorescent reddish orange color (acridine orange) are evidence of acid mucopolysaccharide (glucosaminoglycans) content. The biofilm of a toxigenic strain as opposed to a nontoxigenic one is formed much later, while the elements comprising its structure are more apparent. The viability of vibrio cells during the experiment (90 days) preserving the initial pathogenic potential testifies to the highly adaptable properties of the Vibrio cholerae eltor, which promotes its survival and existence in surface water reservoirs under favorable ecological conditions (optimal temperature, existence of chitin-containing substratum, etc.).

THE INFLUENCE OF SOME FACTORS ON THE FORMATION OF BIOFILM BY TOXIGENIC AND NON-TOXIGENIC VIBRIO CHOLERAE EL TOR STRAINS

The early stages of biofilm formation on polystyrene surface were studied in 14 Vibrio cholerae El Tor strains, all of which carried genes of vps cluster, mshA, and hapR genes. 13 Vibrio cholerae El Tor strains were shown to be capable of adsorption on the walls of microtiter plate wells and of ring formation at the "polystyrene-medium" interface. One of the Vibrio cholerae El Tor strains tested was defective in this ability. The use of different media - modified M1 medium and 1 per cent peptone - failed to reveal sufficient influence of culture medium composition on the ability of Vibrio cholerae to form multilayer biofilm at the phase boundary "polystyrene-medium". Temperature reduction from 37°C to 25°C also didn t result in statistically significant enhancement of monolayer formation in both media. Quantitative evaluation of biofilm formation showed that this ability was clearly marked only in two toxigenic and two non-toxigenic strains of Vibrio cholerae El Tor. Monolayer comparison in ELISA demonstrated that only two toxigenic and two non-toxigenic strains possessed the ability for exopolysaccharide production.