Genetic diversity and virulence gene profiling of Vibrio harveyi in a vibriosis-affected European seabass (Dicentrarchus labrax) aquaculture tank

Aquaculture is crucial for meeting global seafood demand; however, intensification often leads to the development of bacterial diseases that threaten productivity. Dicentrarchus labrax, a key species in European aquaculture, is highly vulnerable to vibriosis, primarily caused by Vibrio harveyi. This study investigates genetic diversity of V. harveyi isolates collected from a seabass tank affected by vibriosis. Sampling from biofilm and water environments yielded 946 bacterial isolates, of which 56 were identified as V. harveyi using MALDI-TOF MS. ERICPCR genotyping revealed four distinct profiles. Despite observing variability in the presence of the 80 virulence genes tested, the overall genetic variation among these profiles was not pronounced. The aim of this study was to determine if the presence of any V. harveyi environmental genotype profile could be used as an early predictor of vibriosis outbreak. Notably, no single environmental genotypic profile was linked to this latter. These findings suggest that the presence of virulence genes alone may not predict disease outbreaks, thus underscoring the need for future research on environmental and transcriptional factors that influences the virulence and pathogenicity to improve disease control in aquaculture systems.