Probiotics inspired from natural ecosystem to inhibit the growth of Vibrio spp. causing white gut syndrome in Litopenaeus vannamei

Abstract

Probiotics inspired by host-microbe interactions in the natural ecosystem are propitious in controlling bacterial infections in aquaculture and veterinary systems. Here we report the isolation and characterization of pathogenic Vibrio spp. and lactic acid bacteria from an intensive culture system of Litopenaeus vannamei and natural ecosystem, respectively. The pathogen isolated from the gut of L. vannamei showing the symptoms of white gut disease were identified as V. parahaemolyticus and V. campbelli. Both the pathogens expressed the virulence genes, rtxA, and tcpA and were showing multiple antibiotic resistance (MAR) index of more than 0.5. The lactic acid bacteria isolated from the sediment and gut of benthic organisms (shrimp and polychaetes) collected from a tropical estuary were classified as member of 9 OTUs such as Pediococcus stilessi, Lactobacillus fermentum, L. rhamnosus, Weissella cibaria, Enterococcus durans, E. fecalis, Streptococcus gallolyticus and L. garvieae. Majority of these isolates were facultative in nature and were able to tolerate gastric juice and bile salt. Out of 83 bacteria isolated from sediment and gut, 36 showed abilities to reduce the pH of culture medium to less than five. Many of these isolates (34 Nos.) showed production of hydrolytic enzymes and secondary metabolites with antagonistic activity against both the pathogens (1 No.) or separately toward V. parahaemolyticus (9 Nos.) and V. campbelli (11 Nos.). Overall, the current study proposes a natural ecosystem as a potential source of lactic acid bacteria with probiotic potentials to prevent the vibriosis disease outbreaks in shrimp aquaculture systems. Further studies are required to understand the abilities of lactic acid bacteria to colonize shrimp intestine, stimulate immune system and manipulate microbiome.