PROBIOTIC CHARACTERISTICS OF LACTOBACILLI FOR RANICULTURE

MONTEL MENDOZA, G.; PASTERIS, S.E.; ALE, C. E.; BUHLER, M.I.; NADER-MACÍAS, M. E.

Tucumán, Argentina

Simposio; III INTERNATIONAL SYMPOSIUM ON LACTIC ACID BACTERIA. II ARGENTINEAN LAB NET MEETING; 2009

Probiotics are used to prevent epizootics in aquaculture. This activity also includes the culture of some amphibian?s species, being Rana catesbeiana the most appropriate. In this area, bacterial infectious diseases such as red leg syndrome (RLS) also named bacterial dermatosepticemia, contributes to the animal mass mortality and therefore to a high impact in the production costs. Thus, the use of probiotics is becoming increasingly popular in aquaculture in order to avoid the use of antibiotics, being Lactic Acid Bacteria (LAB) the most suitable microorganisms for this purpose. In previous studies some LAB, Bifidobacterium and Bacillus were isolated from R. catesbeiana hatcheries. The aim of this study was to evaluate the beneficial properties of lactobacilli that include: a) the production of antagonistic compounds (organic acid, hydrogen peroxide, bacteriocin-like metabolites) against RLS-associated pathogens (Staphylococcus epidermidis, Pseudomonas aeruginosa and Citrobacter  freundii), food borne bacteria (S. aureus, Listeria monocytogenes, and Salmonella enteritidis), and b) lactobacilli surface properties (hydrophobicity and autoaggregation) related with their ability to adhere to epithelial cell surfaces or mucus as well as the biofilm formation. The results show that 72 Lactobacillus strains isolated from different areas of a R. catesbeiana hatchery (dorsal and ventral skin of healthy frogs, and cloaca) from Córdoba inhibited at least one of the pathogens assayed only by organic acid production when tested by the agar well diffusion method. However, a few strains (6) isolated from dorsal skin were able to produce hydrogen peroxide by using a specific method (MRS+TMB+peroxidase).When evaluating the surface properties, most of the strains (62) showed hydrophilic characteristics in relation to their ability to adhere to both intestinal and skin mucus. However, 10 strains presented hydrophobic properties. In this group some strains produced hydrogen peroxide but with the lowest level of antimicrobial activity, except an obligate heterofermentative lactobacilli (strain 362). Moreover, only 6 lactobacillus strains presented autoaggregation characteristics which also showed hydrophobic properties. The results of this work are the basis for the further design of a specie-specific probiotic product able to prevent bacterial diseases in raniculture.