Isolation and screening of lactic acid bacteria producing anti-Edwardsiella from the gastrointestinal tract of wild catfish (Clarias gariepinus) for probiotic candidates

Abstract

Abstract Introduction Members of lactic acid bacteria (LAB) have been well known for their antimicrobial activities against various bacterial pathogens in aquaculture species. Thus, the present study aimed at isolating LAB members from the intestinal tract of wild-caught catfish, Clarias gariepinus, and screening them for antimicrobial production against one of the most common bacterial pathogens, Edwardsiella ictaluri. Material and methods LAB were isolated from the intestinal tract of wild catfish caught at the Brantas River, East-Java Indonesia. Then, LAB were screened for antimicrobial activity against E. ictaluri by in vitro assays and further assessed for probiotic candidates. Results A total of 29 LAB were successfully isolated and further screened for anti-edwarsiella activities. Of the 29, six isolates had strong anti-edwardsiella activity (diameter of inhibition zone, >10 mm). Based on their 16 s rRNA gene sequences, these LABs were identified as Lactococcus lactis, Enterococcus hirae, Weissella confusa, Weissella cibaria, and Enterococcus faecalis (two isolates). Further in vitro assays indicated that E. faecalis, L. lactis, W. confusa, and W. cibaria had good viability in the intestinal tract condition, having good adhesion capacity to intestinal mucus, and being harmless to catfish. However, two species (E. faecalis and W. cibaria) were resistant to novobiocin and enrofloxacin, respectively. Conclusion Three LAB species (E. faecalis, L. lactis, and W. confusa) are potential probiotic candidates in aquaculture to prevent enteric septicemia of catfish disease. However, further studies are needed to evaluate the use of probiotics in vivo.