Highly diverse recombining populations of Vibrio cholerae and Vibrio parahaemolyticus in French Mediterranean coastal lagoons.

Kévin Esteves,Thomas Mosser,Fabien Aujoulat,Patrick Monfort,Estelle Jumas-Bilak,Dominique Hervio-Heath

doi:10.3389/fmicb.2015.00708

Abstract

Vibrio parahaemolyticus and Vibrio cholerae are ubiquitous to estuarine and marine environments. These two species found in Mediterranean coastal systems can induce infections in humans. Environmental isolates of V. cholerae (n = 109) and V. parahaemolyticus (n = 89) sampled at different dates, stations and water salinities were investigated for virulence genes and by a multilocus sequence-based analysis (MLSA). V. cholerae isolates were all ctxA negative and only one isolate of V. parahaemolyticus displayed trh2 gene. Most Sequence Types (ST) corresponded to unique ST isolated at one date or one station. Frequent recombination events were detected among different pathogenic species, V. parahaemolyticus, V. cholerae, Vibrio mimicus, and Vibrio metoecus. Recombination had a major impact on the diversification of lineages. The genetic diversity assessed by the number of ST/strain was higher in low salinity condition for V. parahaemolyticus and V. cholerae whereas the frequency of recombination events in V. cholerae was lower in low salinity condition. Mediterranean coastal lagoon systems housed V. cholerae and V. parahaemolyticus with genetic diversities equivalent to the worldwide diversity described so far. The presence of STs found in human infections as well as the frequency of recombination events in environmental vibrios populations could predict a potential epidemiological risk.

Highlights

The genus Vibrio groups gram-negative halophilic bacteria that are found in marine and estuarine environments, among which some species are responsible for human infections (Colwell et al, 1977)
Many other O serogroups have been reported for cases of V. cholerae associated with diarrhea (Octavia et al, 2013) but the pandemic serogroups O1 and O139 are distinguished by the presence of two genetic elements, the lysogenic bacteriophage designated CTX containing the genes encoding cholera toxin and the Vibrio Pathogenicity Island (VPI) (Sack et al, 2004)
Most of V. cholerae isolated from the environment belong to non-toxigenic non-O1/non-O139 serotypes, Vibrio genetics in Mediterranean lagoons which have been involved in cases of diarrhea (Dutta et al, 2013), some of them carrying various repertories of virulence genes (Octavia et al, 2013)

Summary

Introduction

The genus Vibrio groups gram-negative halophilic bacteria that are found in marine and estuarine environments, among which some species are responsible for human infections (Colwell et al, 1977). Most of V. cholerae isolated from the environment belong to non-toxigenic non-O1/non-O139 serotypes, Vibrio genetics in Mediterranean lagoons which have been involved in cases of diarrhea (Dutta et al, 2013), some of them carrying various repertories of virulence genes (Octavia et al, 2013). Some pathogenic clones encountered an epidemic success that led to the dissemination of the pandemic O3:K6 clone in many countries (Nair et al, 2007) and to the worldwide emergence of other clones such as O4:K8, O4:K11, O4:K12, and O4:K13 as shown in Peru (Gavilan et al, 2013) These vibrios, especially V. parahaemolyticus, are recognized worldwide as agents of gastroenteritis resulting from consumption of raw or undercooked seafood (Tantillo et al, 2004; Pruzzo et al, 2005)

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