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Background. The problem of cholera remains acute for world health service and risks of importation of Vibrio cholerae strains from endemic countries to Russia do exist. Toxigenic strains (carrying cholera toxin genes ctxAB) can cause epidemic outbreaks of cholera and non-toxigenic (ctxAB-) single or multiple cases of cholera-like diarrhea. Investigation of their ability to survive in water reservoirs in climatic conditions of middle latitudes by means of forming biofilms is essential for potential threat evaluation. Materials and methods. Biofilm formation by 15 V. cholerae strains on abiotic surfaces was studied in microcosms with tap water and cover glasses. Identification of responsible genetic determinants in whole genome sequences and bioinformatics analysis were performed using BioEdit 7.2.5, BLASTN 2.2.29, Blastp and Vector NTI Advance 11 software. Results. The strains investigated differed in terms of biofilm formation which correlated with structural features of genes for MSHA pili (msh), matrix polysaccharides (vps) and proteins (rbm) as well as for certain regulatory factors. Strains with none or few genetic deviations from prototypes formed mature biofilms in 5-7 days while those containing truncated genes mshL, mshN, rbmC only in 13 days. One strain with truncated gene for positive regulator vpsR formed an immature biofilm. Acceleration of the process in some strains up to 2-3 days correlated with either truncated gene hapR (negative regulator) or altered structure of both msh and vps-rbm gene clusters. Conclusion. Analysis of genetic determinants responsible for biofilm formation may be used for prediction of V. cholerae ability to survive in environmental objects of Russia and thus the potential danger of the latters as sources of infection.

To the Editor: Cholera—a severe, waterborne, virulent enteric infection caused by toxigenic strains of Vibrio cholera—frequently causes epidemics in developing countries and sporadic cases or local outbreaks in developed countries. The geographic features of Russia and intensive globalization have established favorable conditions for travel-associated cholera from regions to which it is endemic. During 2005–2012, six such cases occurred in Russia; these cases were related to travel from India. Three of the cases were registered in 2010, three months before the cholera outbreak in Haiti, one of the most extensive outbreaks in recent history (1). We genetically analyzed 4 isolates collected in 2010 and 2012 using whole-genome sequencing (Technical Appendix 1) and compared the results with a public database of representative V. cholerae strains (Technical Appendix 2) to identify whether these isolates were linked to cholera in Haiti and Nepal.

We report the draft whole-genome sequences of two Vibrio cholerae O1 strains, the environmental toxigenic strain 2011EL-301 and the clinical nontoxigenic strain P-18785, both isolated in Russia. Some basic data comparing the two against the GenBank repository are provided.