Fast detection of Vibrio species potentially pathogenic for mollusc

A Global Perspective of Vibrio Species and Associated Diseases: Three-Decade Meta-Synthesis of Research Advancement

Outbreaks of Vibrio infections have a long history of global public health concern and threat to the aquaculture industry. This 3-decade (1990-2019) meta-synthesis of global research progress in Vibrio species and associated disease outbreaks was undertaken to generate the knowledge needed to design effective interventions with policy implications. Using PRISMA protocol, we obtained data on the online version of the Institute for Scientific Information (ISI), Web of Science (WOS), and Scopus from January 1990 to September 2021 by title search of the keywords "Vibrio species OR Vibrio spp. OR vibriosis." On the 3-decade survey, the result has shown that a total of 776 publications document types were published on the subject, with an average of 24.25 ± 13.6 published documents per year with an annual growth rate of 4.71%. The year 2020 recorded the highest output of 52 published documents accounting for 6.70% of the total. The most prolific author, Blanch A., published 12 articles on the subject and has received citations of 1003 with an h-index of 10. While the most global cited paper author is the journal of J. Bacteriol (Bassler et al), receiving total citation (TC) (550) and per Year (22). The top active corresponding authors country is the United States of America with (92) articles, freq. 12.40%; TC of 3103. The observations in this study, such as the collaborations network map, and index, which have outlined a big difference between countries based on economic status, have underscored the need for a sustained research mentorship program that can define future policies.

Susceptibility variation to the main pathogens of Crassostrea gigas at the larval, spat and juvenile stages using unselected and selected oysters to OsHV-1 and/or V. aestuarianus

French commercial hatcheries are massively producing Crassostrea gigas selected for their higher resistance to OsHV-1, and soon should also implement selection for increasing resistance to Vibrio aestuarianus. The first objective of this study was to optimize the breeding programs for dual resistance to OsHV-1 and V. aestuarianus to determine the earliest life stage for which oysters are able to develop disease resistance. Wild stocks and selected families were tested using experimental infections by both pathogens at the larval, spat and juvenile stages. Oyster families could be evaluated for OsHV-1 as soon as the larval stage by a bath method, but this only highlighted the most resistant families; those that showed the highest resistance to V. aestuarianus could be determined using the cohabitation method at the juvenile stage. The second objective of this study was to determine if selection to increase/decrease the resistance to OsHV-1 and V. aestuarianus could have an impact on other major pathogens currently detected in hatchery at the larval stage, and in nursery and field at the spat/juveniles stages (V. coralliilyticus, V. crassostreae, V. tasmaniensis, V. neptunius, V. europaeus, V. harveyi, V. chagasi). No relationship was found between mortality caused by V. aestuarianus/OsHV-1 and the mortality caused by the other virulent bacterial strains tested regardless the stages, except between OsHV-1 and V. tasmaniensis at the juvenile stage. Finally, miscellaneous findings were evidenced such as (1) bath for bacterial challenges was not adapted for spat, (2) the main pathogens at the larval stage were OsHV-1 and V. coralliilyticus using bath, while it was V. coralliilyticus, V. europaeus, and V. neptunius at the juvenile stage by injection, and (4) variation in mortality was observed among families/wild controls for all pathogens at larval and juvenile stages, except for V. harveyi for larvae.

Increased survival of juvenile turbot Scophthalmus maximus by using bacteria associated with cultured oysters

Preventing vibriosis in juvenile cultured Turbot Scophthalmus maximus caused by Vibrio anguillarum frequently requires the use of feed supplemented with antibiotics in addition to vaccines. Whether the use of probiotics instead of antibiotics in juvenile Turbot is a safer strategy requires more study. The antibacterial potential of 148 Vibrio spp. strains (mostly isolated from cultures of healthy oysters, clams, and Turbot) was analyzed in vitro against V. anguillarum and other pathogens by means of an agar diffusion assay. A wide spectrum of inhibitory activity was shown by 9 strains. Based on their easy phenotypic differentiation from V. anguillarum, we selected two strains (S1 and S2, both isolated from the European flat oyster Ostrea edulis) for testing in juvenile Turbot (3 g). None of the strains were virulent by intraperitoneal or bath challenges, and all were susceptible to the antibiotics most frequently used in aquaculture. Three different stocks of Turbot, which were assayed separately, were significantly protected from infection with V. anguillarum. The final survival rates of fish treated in mixed challenges with S1 or S2 and V. anguillarum were 44% and 66%, respectively, whereas only 17% of the fish treated with only the pathogenic strain survived. The application of probiotic strains also increased the survival time of juvenile Turbot after infection with V. anguillarum. Both strains persisted in the epidermal mucus layer of the fish for 30 d, and they were not displaced by the pathogen. These data prove the efficacy of using bacteria well adapted to the dynamics of culture production as a way to provide juvenile Turbot immediate protection against infection by V. anguillarum. Moreover, the epidermal mucus sampling was useful for investigating the persistence of both probiotic strains when exposed to the pathogen.

Mar Piccolo of Taranto: Vibrio biodiversity in ecotoxicology approach

Microorganisms play an indispensable role in the ecological functioning of marine environment. Some species are sensitive while others are insensitive for a specific pollutant. The aim of this work is a preliminary study of the quantitative and qualitative distribution of cultivable vibrios in sediments and water samples characterized by different toxicity levels. For 1 year, in three suitably selected sampling stations of Mar Piccolo in Taranto (Ionian Sea, Italy), we have evaluated the toxicity level by Microtox® system, vibrios, total, and fecal coliform densities. The results of the Microtox® tests showed sediments characterized by an elevated level of toxicity, while the interstitial water of the same sites always showed biostimulatory phenomenon. The quantitative results show that vibrios and coliforms are more abundant in water than in sediment samples. The most often isolated strains were: Vibrio alginolyticus, Vibrio mediterranei, Vibrio metschinkovii, and Vibrio splendidus II. This work is the first example of study on the distribution of Vibrio species related to toxicity evaluation conducted by the Microtox® bioassay. The results show the different distribution of Vibrionaceae in two environmental matrices analyzed and characterized by different levels of toxicity.