Investigation of pathogenic and toxigenic vibrio in Irish aquaculture

In recent years marine waters have warmed, causing more favourable environments for Vibrio species. With climate change, the distribution of Vibrio marine pathogens is expected to expand leading to an increase in pathogenic and toxigenic Vibrio throughout Europe posing a greater threat to human health and aquaculture. Vibrio vulnificus, V. parahaemolyticus and V. cholerae are causative agents of gastroenteritis in humans. Furthermore, opportunistic Vibrio species such as V. alginolyticus have been implicated in rising human and aquaculture infection. Reports on the presence of Vibrio species in Irish waters is sparse. V. parahaemolyticus is largely connected with seefood associated gastroenteristis. Genomics revealed the presence of Type III Secretion System 2 (T3SS2) complexes and an array of pathogenic genes responsible for host colonisation and infections. This study uses a combination of culture, molecular and genomic methods to explore the occurrence, phylogeny and pathogenicity of the dominant Vibrio community. Shellfish, water and sediment samples were sourced from 5 prominent aquaculture sites located at the north and west of Ireland over a minimum of 12-month to provide a view on the naturally present and potentially pathogenic Vibrio. From this study, a diverse Vibrio community was identified at prominent coastal Irish aquaculture sites. The pathogen V parahaemolyticus along with a number of Vibrio species; Vibrio alginolyticus, Vibrio diabolicus, Vibrio jasicida, Vibrio metschnikovii and Vibrio proteolyticus were detected over the course of the study. The dominant Vibrio species detected from Irish oysters and mussels was V. diabolicus and opportunistic pathogen V. alginolyticus. Molecular and genomic analysis of Vibrio genomes identified the presence of potentially pathogenic V. parahaemolyticus and V. diabolicus isolates. The presence of V. diabolicus isolates containing the Type III Secretion System 2β (T3SS2β) with high homology to the virulent T3SS2β V. parahaemolyticus was observed through genomic comparison of whole genome sequenced isolates. Furthermore, potential for antimicrobial resistance and biosynthetic potential was uncovered using a genome mining approach. Tetrodotoxin (TTX) is a potent neurotoxin demonstrating a wider distribution throughout European waters. The biosynthesis of TTX in Vibrio remains complex and unclear. This study set out to provide a comparative whole genome sequencing approach to investigate possible TTX producing Vibrio genes. This study provides a comprehensive review on the bacterial biosynthesis of tetrodotoxin with a focus on determining a molecular target. Immunological and UPLC-MS methods were explored to provide analysis on the toxigenic potential of Irish Vibrio and Shewanella with the aim of gaining insight into the TTX producing capabilities of Irish bacterial isolates

Funder

Department of Agriculture, Food and the Marine

Publisher

University of Galway

Rights

Attribution-NonCommercial-NoDerivatives 4.0 International

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Collections

University of Galway Theses (Research Masters Theses)