Seafood products are widely consumed all around the world and play a significant role on the economic market. Bacteria of the Vibrio genus can contaminate seafood and thus pose a risk to human health. Three main Vibrio species, V. cholerae, V. parahaemolyticus and V. vulnificus, are potentially pathogenic to humans. These species are responsible for a dramatic increase of seafood-borne infections worldwide. Hence, early detection of total and pathogenic Vibrio is needed and should rely on quick and effective methods. This review aims to present the standard methods FDA-BAM, ISO/TS 21872–1:2007 and TS 21872–2:2007 and compare them to recent molecular biology methods including endpoint PCR, quantitative real-time PCR (qPCR) and PCR-derived methods with a focus on LAMP (loop-mediated isothermal amplification). The available methods presented here are dedicated to the detection and identification of the Vibrio species of interest in seafood.

Vibrio bacteria, and particularly members of the Harveyi clade, are the causative agents of vibriosis. This disease is responsible for mass mortality events and important economic losses on aquaculture farms. Improvements in surveillance and diagnosis are needed to successfully manage vibriosis outbreaks. 16S rRNA gene sequencing is generally considered to be the gold standard for bacterial identification but the cost and long processing time make it difficult to apply for routine identification. In contrast, MALDI-TOF MS offers rapid diagnosis and is commonly used in veterinary laboratories today. The major limiting factor for using this technique is the low environmental bacterial diversity in the commonly available databases. Here, we demonstrate that the sole use of the commercially available Bruker BioTyper database is not fully adequate for identifying Vibrio bacteria isolated from aquaculture farms. We therefore developed a new in-house database named Luvibase, composed of 23 reference MALDI-TOF mass spectra profiles obtained from Vibrio collection strains, mostly belonging to the Harveyi clade. The comparison of the accuracy of MALDI-TOF MS profiling and 16S rRNA gene sequencing revealed a lack of resolution for 16S rRNA gene sequencing. In contrast, MALDI-TOF MS profiling proved to be a more reliable tool for resolving species-level variations within the Harveyi clade. Finally, combining the Luvibase with the Bruker ver.9.0.0.0 database, led to successful identification of 47 Vibrio isolates obtained from moribund abalone, seabass and oysters. Thus, the use of Luvibase allow for increased confidence in identifying Vibrio species belonging to the Harveyi clade.

Nowadays, European seabass (Dicentrarchus labrax) aquaculture is undergoing a significant expansion. Nevertheless, the aquaculture industry is plagued by vibriosis. The spatial and temporal dynamics of Vibrio harveyi were studied on a European seabass farm in northern France during seven months of 2022. Concrete specimens were suspended and water was pumped from different depths (0.3 m, 2.15 m and 4 m deep), providing insights into the biofilm and planktonic V. harveyi dynamics. The abundances of V. harveyi, in the biofilm and free-living forms, were positively correlated. The water parameters revealed seasonal fluctuations in temperature, pH, and salinity, with no significant differences observed across the water column. Quantification of V. harveyi revealed no significant differences between depths, but seasonality, with peak abundances observed in August, correlated with temperature increases. Principal component analysis identified temperature as a primary driver, but also additional parameters, such as salinity and pH. Vibriosis occurred during the sampling period, providing valuable insights into the conditions before, during, and after the outbreaks. This study underscores the importance of understanding V. harveyi behaviour in aquaculture, particularly in the context of global warming, for effective disease management and sustainable practices.

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. ERIC-PCR 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.

La palourde japonaise, Venerupis philippinarum, a été introduite en France au début des années 70 à des fins aquacoles. Depuis 1987, d’importants épisodes de mortalité, causés par la bactérie pathogène Vibrio tapetis, touchent cette espèce le long des côtes françaises et européennes. Cette vibriose, appelée Maladie de l’Anneau Brun (MAB), est considérée comme une maladie d’eau froide. L’interaction tripartite entre V. philippinarum, V. tapetis et l’environnement a été explorée à travers le rôle du système enzymatique des phénoloxydases (POs) dans le but de mieux comprendre la réponse immunitaire de la palourde japonaise, la virulence de l’agent pathogène mais aussi l’impact de l’environnement et plus particulièrement de la température. Les POs sont des oxydoréductases impliquées dans la synthèse de la mélanine et de ses dérivés mais aussi dans les processus de reconnaissance du non-soi et d’encapsulation chez les invertébrés. Dans un premier temps, l’activité PO du sérum d’hémolymphe a été caractérisée d’un point de vue biochimique comme étant majoritairement de type laccase ; une activité minoritaire de type tyrosinase a également été identifiée. Des infections de palourdes par trois souches de V. tapetis, à différentes températures, ont mis en évidence une modulation de la réponse du système PO en fonction du temps et du compartiment étudiés. De façon générale, l’infection bactérienne s’est traduite par une augmentation de l’activité PO. Toutefois, le niveau basal d’activité PO est variable d’une population à une autre et cette variabilité semble traduire une susceptibilité différente à la MAB. L’augmentation de la température de 15 à 22°C a entraîné une augmentation des capacités immunitaires de la palourde japonaise. La températurea également eu un impact sur la pathogénicité de V. tapetis et ce, de façon différentielle selon les souches. L’inhibition de l’activité PO observée in vitro en présence de produits extracellulaires bactériens souligne la complexité de l’interaction entre V. philippinarum et V. tapetis. Ainsi, le suivi de l’activité PO constitue un biomarqueur pertinent des capacités immunitaires des invertébrés marins dans l’interaction tripartite hôte-pathogène-environnement.