Bacteria with probiotic characteristics isolated from Patagonian fish.

MARISA GARCÉS; NELDA LILA OLIVERA; CYNTHIA SEQUEIROS

Valparaíso

Simposio; Latin America Zebrafish Network Symposium; 2014

ICGEB

Bacterial diseases are a major problem for aquaculture development. Misuse and abuse of antibiotics to treat or prevent microbial diseases has led to the emergence of resistant pathogens and antibiotic accumulation inside of the fish organs. For an environmentally sustainable aquaculture, the use of probiotics is an interesting alternative. Probiotics, which are microorganisms or their products with beneficial effects for the host health, are useful to control diseases of aquatic organisms by supplementing or even replacing the use of antibiotics. On the other hand, zebrafish (Danio rerio) has become a model organism for genetic, developmental, and drug discovery studies. More recently, zebrafish has been used as a model to evaluate the effects of the probiotic Lactobacillus rhamnosus on its reproduction. We have studied in vitro some probiotic characteristics of bacteria isolated from the intestinal microbiota of Patagonian fish. We assessed production of antimicrobial substances, tolerance to fish bile, adhesion capability, and sensitivity to antibiotics. Three strains isolated from rainbow trout showed antimicrobial activity against the fish pathogen Carnobacterium piscicola, in addition one of them also inhibited Lactococcus garvieae, the etiological agent of lactococcosis. Antimicrobial activity of these three strains remained stable after treatment at 100°C for 10 min (at pH 7) suggesting that the antimicrobial agent could be a bacteriocin. Moreover, one strain isolated from the intestinal tract of hake (Merluccius hubbsi) showed extracellular antimicrobial activity against Vibrio alginolyticus and Aeromonas salmonicida. Such activity was not observed when the culture supernatant was neutralized. Therefore, the inhibitory activity could be attributed to organic acid production. Two strains showed higher specific adhesion to fish skin mucus than to other surfaces such as glass. We conclude that these strains are promising candidates to be used as biological control agents in aquaculture. Current in vivo experiments are being conducted to evaluate the probiotic capabilities of these bacteria using the zebrafish as a model.