Characterization of probiotic carnobacteria isolated from rainbow trout (Oncorhynchus mykiss) intestine

Aims: To characterize two probiotic carnobacterial isolates, Carnobacterium maltaromaticum (B26) and C. divergens (B33), derived from rainbow trout (Oncorhynchus mykiss) intestine. Methods and Results: Both cultures, which were able to colonize the fish gut mucosal layer, comprised nonsporogenous, nonmotile, Gram-positive, catalase and oxidase-negative rods. The growth of both carnobacteria occurred between 0 and 37°C, in 0-10% (w/v) NaCl and at pH 5-10. Specifically, strain B26 grew in nutrient broth supplemented with 15% (w/v) NaCl. The most abundant cellular fatty acid of both cultures was 9-octadecenoic acid (18:1 n-9) (B26 = 52·6%; B33 = 40·6%), which was characteristic of Carnobacterium. Both cultures were inhibitory to Aeromonas salmonicida, Aer. hydrophila, Streptococcus iniae and Vibrio anguillarum, and strain B33 inhibited Listeria monocytogenes. Both carnobacteria, which did not contain plasmids, produced inhibitory compounds against Gram-positive and Gram-negative bacteria. Conclusions: Both probiotic cultures, B26 and B33, had unique phenotypic characteristics and showed a broad spectrum of antibiotic resistance against varying pathogenic bacteria. Significance and Impact of the Study: The results of this study contribute to new information and significance of carnobacterial species. © 2008 The Authors.