Development and evaluation of a formulation of probiont Phaeobacter inhibens S4 for the management of vibriosis in bivalve hatcheries

Abstract

Larval eastern oysters (Crassostrea virginica) grown in shellfish hatcheries are susceptible to bacterial diseases, particularly vibriosis. Probiotics are microbes that confer health benefits to the host and have been identified as promising tools to manage diseases in aquaculture. The marine bacterium Phaeobacter inhibens S4 (S4) protects larval eastern oysters against challenge with the bacterial pathogen Vibrio coralliilyticus RE22 (RE22). A concentrated liquid formulation of probiont S4 that maintained high cell viability after long‐term storage was developed for commercial use in shellfish hatcheries. The safety and efficacy of the formulation were tested in six different trials in two hatcheries. The S4 formulation was added to C. virginica larvae culture tanks daily at 104 colony forming units (CFU)/mL from Day 1 post fertilisation until Day 6, 12 or 14, depending on the trial. Treatment of larvae in the hatchery with the S4 formulation did not significantly affect the survival and growth of the larvae. Formulated probiont S4 treatment in the hatchery led to a significant increase in relative percent survival (RPS) when larvae were subsequently challenged with the pathogen RE22 (105 CFU/mL) for 24 h in a laboratory challenge as compared to probiotic‐untreated RE22‐challenged larvae (RPS increase of 46%–74%, p < 0.05). These results suggest that this novel S4 formulation is a safe, easy‐to‐use and effective tool in preventing larval losses due to vibriosis in hatcheries.

Microbial education plays a crucial role in harnessing the beneficial properties of microbiota for infectious disease protection inCrassostrea gigas

“…A diversity of studies on oystermicrobiota interactions have also opened a new field of investigations consisting in identifying bacteria beneficial for their associated host during adverse conditions (King et al 2019a;Clerissi et al 2020;Delisle et al 2022;Fallet et al 2022). Research on disease prevention in molluscs based on the use of probiotics has been ongoing for decades but has yet to see widespread applications in farms (Yeh et al 2020;Takyi et al 2023Takyi et al , 2024Muñoz-Cerro et al 2024). While several pre/probiotic-based methods to mitigate infectious diseases have demonstrated success in shrimp hatcheries (Swain et al 2009;Pham et al 2014;Wen et al 2014), their application in oyster farming, particularly in open-sea environments, faces distinct challenges and limitations.…”

The Probiotic Bacillus hwajinpoensis Colonizes the Digestive System of Crassostrea gigas Larvae and Protects Them from Vibrio alginolyticus Infection

“…The antibiotics have been applied to kill or inhibit pathogenic Vibrio growth [13,15]. While the overall effect of antibiotics varies considerably among cases, antibiotic usage is discouraged because of bacteria's potential development of resistance and negative impacts on healthy microbiota [18,19].…”

“…Several studies investigated certain mechanisms behind the beneficial effects, such as pathogen inhibition, secretion of antimicrobials, immunomodulation, host growth promotion, competition for nutrients with pathogens, and improvement of water quality [22,23,25]. For example, Phaeobacter inhibens S4 (S4) and Bacillus pumilus RI06-95 (RI) protect larval Eastern oysters (Crassostrea virginica) from Vibrio coralliilyticus RE22 infection through different mechanisms [19,26]. The health benefits of S4 were derived from biofilm formation, secretion of the antibiotic tropodithietic acid, quorum quenching, and host immune modulation [25,27,28].…”