Conservation of cholera vibrios in complex microcosm containing green microalgae

BACKGROUND: In the summer-autumn period, the peak of phytoplankton reproduction and flowering occurs and results in the deterioration of the quality of river water is noted. At the same time, cases of gastrointestinal diseases in humans are recorded, and epidemic complications of cholera may occur in endemic areas. V. cholerae form biofilm on the surface of chitinous hydrobionts and plastic components can lead to the spread of V. cholerae, possibly explaining the autochthonous mechanism of their existence in water bodies.

AIM: This study determines the duration of Vibrio cholerae preservation on biotic (chitin) and abiotic (plastic) substrates in the presence of green unicellular algae with a change in cultivation temperature under experimental conditions.

MATERIALS AND METHODS: This study used bacteriological and molecular genetic methods to achieve its goal.

RESULTS: The preservation of toxigenic and non-toxigenic strains of V. cholerae O1 El Tor and V. cholerae O139 (ctxАВ⁺tcpА⁺csh1^– and ctxА^–tcpА^–csh1⁺) for six months, including three months at a low temperature simulating the autumn-winter period, as part of biofilms in microcosms, where one component is green microalgae. We noted an excess of the concentration of V. cholerae O1 and O139 serogroups by two orders of magnitude in samples where one of the components is chitin and the reproduction of green microalgae in the presence of a chitin substrate. This is probably one stage in the food chain in the ecology of water bodies and, accordingly, can be a reservoir for biofilm forms of cholera vibrios. Preservation of V. cholerae O1 El Tor non-toxigenic strain in a viable state in biofilm samples on plastic at decreased temperatures 8±2°C for three months is possibly due to the presence of a cold shock gene in its genome.

CONCLUSION: Without a substrate for adhesion, colonization, and biofilm formation, vibrios are incapable of long-term persistence at low temperatures.