Probiotics in aquaculture

Abstract

Probiotics, which are micro-organisms or their products with health benefit to the host, have found use in aquaculture as a means of disease control, supplementing or even in some cases replacing the use of antimicrobial compounds. A wide range of microalgae (Tetraselmis), yeasts (Debaryomyces, Phaffia and Saccharomyces) and Gram-positive (Bacillus, Carnobacterium, Enterococcus, Lactobacillus, Lactococcus, Micrococcus, Streptococcus and Weissella) and Gram-negative bacteria (Aeromonas, Alteromonas, Photorhodobacterium, Pseudomonas and Vibrio) has been evaluated. However, the mode of action of the probiotics is rarely investigated, but possibilities include competitive exclusion, i.e. the probiotics actively inhibit the colonization of potential pathogens in the digestive tract by antibiosis or by competition for nutrients and/or space, alteration of microbial metabolism, and/or by the stimulation of host immunity. Probiotics may stimulate appetite and improve nutrition by the production of vitamins, detoxification of compounds in the diet, and by the breakdown of indigestible components. There is accumulating evidence that probiotics are effective at inhibiting a wide range of fish pathogens, but the reasons for the inhibitions are often unstated

Probiotics in aquaculture of China — Current state, problems and prospect

“…Most studies on the effects of probiotics on cultured aquatic animals have emphasized a reduction in mortality or the improved resistance against putative pathogens (Irianto and Austin, 2002). However, the beneficial effects are sometimes temporal, depending on the time of exposure (Verschuere et al, 2000).…”

“…At present, probiotics are well established for use in humans, poultry and cattle. The probiotics could be considered as veterinary medicine used for animal protein production (Irianto and Austin, 2002). In the field of aquaculture, Verschuere et al (2000) extended the concept of probiotic as " a live microbial adjunct which has a beneficial effect on the host by modifying the host-associated or ambient microbial community, by ensuring improved use of the feed or enhancing its nutritional value, by enhancing the host response towards disease, or by improving the quality of its ambient environment".…”

Diversity of cutaneous bacteria with antifungal activity isolated from female four-toed salamanders

“…and Saprolegnia sp.). Flavobacterium strains have been used as probiotics and growth promoters in algae (Chaetoceros gracilis) (Verschuere et al, 2000;Irianto and Austin, 2002). It seems reasonable that bacteria related to these biocontrol agents will work as powerful disease preventing agents against amphibian pathogens on their skin and embryos.…”

“…Some antifungal bacteria or their metabolites are used in marine and freshwater aquaculture to reduce the susceptibility of the animals toward microbial pathogens including fungi (Gil-Turnes and Fenical, 1992;Verschuere et al, 2000;Irianto and Austin, 2002). A cutaneous microbiota that includes antifungal species may be important for the health of adult and embryonic amphibians.…”

Testing the efficacy of probiotics for disease control in aquaculture

“…Probiotics can inhibit the growth of pathogens in the gut through the excretion of antagonistic substances including bacterocins 6,7 ; prevent pathogen adhesion in the gut through competition of space and nutrients 3 and by modulating the immune system 5 . Some probiotics have been reported to improve growth and feed utilisation efficiency 5 and others can also improve water quality 2,8,9 , which confers indirect benefits to host health 6 .It has been estimated that 50 000 tonnes of probiotics are used annually in the aquaculture industry 10 yet analysis of the literature reveals a great deal of equivocal data on their efficacy. This is likely due, at least in part, to the wide diversity of both hosts and probiotic species within this industry and the fact that probiotic efficacy against particular pathogens is often both host specific and probiotic strain specific 5 .…”