Abstract
BackgroundV. parahaemolyticus is autochthonous to the marine environment and causes seafood-borne gastroenteritis in humans. Generally, V. parahaemolyticus recovered from the environment and/or seafood is thought to be non-pathogenic and the relationship between environmental isolates and acute diarrhoeal disease is poorly understood. In this study, we explored the virulence potential of environmental V. parahaemolyticus isolated from water, plankton and assorted seafood samples collected from the Indian coast.ResultsTwenty-two V. parahaemolyticus isolates from seafood harboured virulence associated genes encoding the thermostable-direct haemolysin (TDH), TDH-related haemolysin (TRH), and Type 3 secretion systems (T3SS) and 95.5% of the toxigenic isolates had pandemic strain attributes (toxRS/new+). Nine serovars, with pandemic strain traits were newly identified and an O4:K36 tdh−trh+V. parahaemolyticus bearing pandemic marker gene was recognised for the first time. Results obtained by reverse transcription PCR showed trh, T3SS1 and T3SS2β to be functional in the seafood isolates. Moreover, the environmental strains were cytotoxic and could invade Caco-2 cells upon infection as well as induce changes to the tight junction protein, ZO-1 and the actin cytoskeleton.ConclusionOur study provides evidence that environmental isolates of V. parahaemolyticus are potentially invasive and capable of eliciting pathogenic characteristics typical of clinical strains and present a potential health risk. We also demonstrate that virulence of this pathogen is highly complex and hence draws attention for the need to investigate more reliable virulence markers in order to distinguish the environmental and clinical isolates, which will be crucial for the pathogenomics and control of this pathogen.
Highlights
V. parahaemolyticus is autochthonous to the marine environment and causes seafood-borne gastroenteritis in humans
Identification of V. parahaemolyticus from the environment Four hundred and seventeen V. parahaemolyticus isolates were identified from environmental and seafood samples collected through five districts of the coastal belt of Kerala during the sampling period
The present study examined the distribution of virulence related genes in 417 V. parahaemolyticus isolated from the environment and seafood and focused on tdh and/or trh isolates to determine the pathogenicity
Summary
V. parahaemolyticus is autochthonous to the marine environment and causes seafood-borne gastroenteritis in humans. V. parahaemolyticus recovered from the environment and/or seafood is thought to be non-pathogenic and the relationship between environmental isolates and acute diarrhoeal disease is poorly understood. We explored the virulence potential of environmental V. parahaemolyticus isolated from water, plankton and assorted seafood samples collected from the Indian coast. Though a majority of clinical V. parahaemolyticus generally carry tdh and/or trh, only a small proportion of environmental isolates have been found to harbour the hemolysin genes [6,7,8]. The environmental population of V. parahaemolyticus is increasingly acquiring the virulence-related genes that classically define a clinical isolate [10, 11]. The true pathogenic potential of such strains has not been evaluated at large
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