The present study aimed to investigate the potential probiotic properties in fish of a lactic acid
bacterium intended for human use: Lactobacillus rhamnosus ŽATCC 53103.. A probiotic for
human use was specifically chosen since it is known to be safe for human use, which is of major
importance because the fish are meant for human consumption. The bacterium was administered at
two different doses Ž109 and 1012 CFUrg feed. to rainbow trout for 51 days. Sixteen days after
the start of the Lactobacillus feeding, the fish were challenged with Aeromonas salmonicida ssp.
salmonicida, which causes furunculosis. During the challenge trial the mortality was monitored.
L. rhamnosus reduced the fish mortality significantly, from 52.6% in the control to 18.9% and
46.3% in the 109 CFUrg feed and the 1012 CFUrg feed groups, respectively. From this, it was
concluded that the tested strain may be a promising probiotic for fish without subsequent risk for
human consumption. q2001 Elsevier Science B.V. All rights reserved.