The impact of pathogen-pathogen and host-pathogen signaling on the virulence of Vibrio harveyi towards gnotobiotic brine shrimp (Artemia franciscana) larvae

Subtitle:De impact van pathogeen-pathogeen en gastheer-pathogeen communicatie op de virulentie van Vibrio harveyi tegenover gnotobiotische pekelkreeftjes (Artemia franciscana)

Vibrio harveyi is amongst the most significant pathogens in the larviculture and aquaculture industry. It can affect a wide range of marine vertebrates and invertebrates, causing significant losses to the aquaculture industry worldwide. However, the pathogenicity mechanism of V. harveyi is not yet completely understood. In this work, we evaluated the impact of pathogen-pathogen signaling and sensing of host factors on the virulence of V. harveyi in a model system with gnotobiotic brine shrimp larvae. Our results suggested that quorum sensing, the bacterial cell-to-cell communication, positively regulated motility by affecting flagellar biosynthesis through LuxR, and that flagellar motility significantly affected virulence of V. harveyi in our gnotobiotic brine shrimp model. The inhibition of quorum sensing is a promising alternative strategy to control disease, nine quorum sensing-disrupting thiophenones were considered to be highly promising in this study. We proposed a new parameter AQSI, which was regarded as a straightforward and elegant way to exclude false positives by taking into account side effects related to the use of quorum sensing molecule reporters. Additionally, indole sensing was found to be able to reduce the virulence of V. harveyi towards gnotobiotic brine shrimp larvae and conventionally reared giant river prawn larvae. Indole also decreased the production of several virulence factors in V. harveyi. Finally, the host stress hormones norepinephrine and dopamine increased the virulence of V. harveyi by increasing swimming motility, biofilm formation, exopolysaccharide production and growth in environments with low iron availability. In conclusion, the work presented in this thesis indicates the complexity of the virulence mechanisms in V. harveyi and proposes a novel mechanism by which indole and host factors regulate the virulence of V. harveyi. Additionally, thiophenones are found to be promising antivirulence agent for infections caused by V. harveyi.

ISBN:9789059898448

Publication year:2015

Accessibility:Open