In vitro assessment on intestinal microfora from commonly farmed fshes for control of the fsh pathogen Edwardsiella tarda

Abstract

This study was aimed to evaluate the microfora isolated from the intestines of tilapia ( Oreochromis niloticus), freshwatercatfsh (Clarias batrachus), snakehead (Ophicephalus striatus), snakeskin gourami (Trichogaster pectoralis), climbing perch ( Anabastestudineus), and river catfsh (Pangasius pangasius) for their potential probiotic development. Isolates were initially screened for theirinhibitory efect against one of the most common fsh pathogens, Edwardsiella tarda . Positive antagonists were subsequently tested forhemolytic activity, antibiotic susceptibility, and production of bacteriocin-like inhibitory substances (BLISs). Our results revealed 55of the 405 isolates tested showed inhibitory effects towards the pathogen. Forty isolates were γ-hemolytic bacteria. Only 7 isolates werenonresistant to tested antibiotics. Tey were identifed as Lactococcus lactis based on 16S rRNA characterization. Our BLIS data suggestthat L. lactis subsp. lactis CF4MRS at the cell density of 106 cfu/mL could be effectively used to control E. tarda .