Updating the Importance of Lactic Acid Bacteria in Fish Farming: Natural Occurrence and Probiotic Treatments

Abstract

Many recent papers have deepened the state of knowledge about lactic acid bacteria (LAB) in fish gut. In spite of high variability in fish microbiota, LAB are sometimes abundant in the intestine, notably in freshwater fish. Several strains of Streptococcus are pathogenic to fish. Streptococcus iniae and Lactococcus garvieae are major fish pathogens, against which commercial vaccines are available. Fortunately, most LAB are harmless, and some strains have been reported for beneficial effects on fish health. A major step forward in recent years was the converging evidence that LAB can stimulate the immune system in fish. An open question is whether viability can affect immunostimulation. The issue is crucial to commercialize live probiotics rather than inactivated preparations or extracts. There has been a regain of interest in allochthonous strains used as probiotics for terrestrial animals or humans, due to economical and regulatory constraints, but the short survival in sea water may limit application to marine fish. If viability is required, alternative treatments may include the incorporation of prebiotics in feed, and other dietary manipulations that could promote intestinal LAB. Antagonism to pathogens is the other main feature of candidate probiotics, and there are many reports concerning mainly carnobacteria and Enterococcus. Some bacteriocins were characterized which may be of interest not only for aquaculture, but also for food preservation.

Effect of probiotic supplemented diet on marine shrimp survival after challenge with Vibrio harveyi

“…This would be related to the capacity of lactic bacteria to produce antimicrobial compounds such as hydrogen peroxide, bacteriocins (like reuterins), lactic acid, and other organic acids. In addition, lactic bacteria present in the digestive tract can also produce immunostimulating substances (Gatesoupe, 2008).…”

“…Recently, an alternative that has been widely employed in the aquaculture industry is the dietary supplementation with probiotic bacteria (Gatesoupe, 1999;Vine et al, 2006). Gatesoupe (1999) defines probiotics as "live microbial cells administered to cultured organisms to colonize the digestive tract and improve their immune response".…”

“…Gatesoupe (1999) defines probiotics as "live microbial cells administered to cultured organisms to colonize the digestive tract and improve their immune response".…”

“…Among the probiotic bacteria used in aquaculture, the lactic acid bacteria stand out for their easy multiplication, production of antimicrobial compounds (bacteriocins, hydrogen peroxide, organic and lactic acids), and the stimulation of the non-specific immune response of the host (Gatesoupe, 2008). Studies have demonstrated the beneficial effect of the addition of such bacteria in the culture of several aquatic species (Gatesoupe, 2008).…”

“…Studies have demonstrated the beneficial effect of the addition of such bacteria in the culture of several aquatic species (Gatesoupe, 2008). Nevertheless, only a few studies have been conducted to assess the use of lactic acid bacteria strains isolated from marine shrimp.…”