CHARACTERIZATION OF A LACTIC ACID BACTERIA ISOLATED FROM FISH TO SELECT IT AS A PROBIOTIC FOR PREVENTION OF INFECTIOUS DISEASES IN RAINBOW TROUT CULTURE

MARÍA GABRIELA SICA; LORENA BRUGNONI; PATRICIA MARUCCI; MARÍA AMELIA CUBITTO

San Miguel de Tucumán

Congreso; VII Congreso Argentino de Microbiología General.; 2011

Sociedad Argentina de Microbiología General

The present study aimed to investigate the probiotic properties of a lactic acid bacteria (LAB), F2, isolated from the skin and intestinal content of the fish Ramnogaster arcuata from Bahía Blanca Estuary, Argentina, by examining its in vitro adhesion to rainbow trout mucus, competitive exclusion of salmonid pathogens (Yersinia ruckeri and Aeromonas salmonicida), pH and rainbow trout bile tolerances and characterize cell surface properties. According to 16S rDNA phylogenetic analysis, the isolate was affiliated as Lactobacillus paracasei subsp tolerans (GenBank accession FJ892732), and was selected for this study by presenting growth inhibitory effects against the salmonid pathogens: A. salmonicida subsp. salmonicida, Y. ruckeri and two strains of Lactococcus garvieae. Lactobacillus paracasei subsp tolerans showed high resistance at pH 3.0 and no change in viable count were observed and tolerate pH 2.0 with reduction of 4 log, with respect to control (pH 6.5). This strain tolerated fish bile concentration of 10% for 1.5 h of incubation and no significant changes in viable counts compared to the control were observed. The cell surface hydrophobicity, expressed as affinity for n-hexadecane, and the aggregation and co-aggregation properties were investigated. The strain F2 assayed showed low ability of autoaggregate and coaggregate, and displayed a hydrophilic nature. The LAB strain was able to attach to rainbow trout skin mucus, glass and stainless steel, between 104-105 cells/cm2. The strain F2 was capable to inhibiting the attachment of salmonid pathogens, Y. ruckeri and A. salmonicida, to mucus at different degree, in the competitive exclusion conditions tested: competition, exclusion and displacement. In base to the observed characteristics in this study and the antagonist activity against salmonid pathogens, previously determined, our data suggest a probiotic potential of Lactobacillus paracasei subsp tolerans as anti-infective agent in the rainbow trout culture