Theses and Dissertations


Name: Maxwell, Vanessa Jane

Degree: MS

Chair: Ronald P. Phelps


University: Auburn University

Location: Auburn, Alabama

Date: 2003

Pages: 71

Keywords: probiotics,red snapper


Probiotics are viable cultures of microorganisms that have a beneficial affect when given to an animal. Probiotics have only recently been researched for application in the aquaculture industry, particularly with the first feeding of larval fish. A protocol was developed for the probiotic potential of bacteria isolated from the intestine of adult red snapper, Lutjanus campechanus, and the water used for larval culture. Thirty-four different bacteria were isolated from the adult red snapper representing various species including the pathogen Vibrio parahaemolyticus. Fourteen isolates of gram positive cocci were obtained from the water source along with an additional fourteen presumed Vibrio sp. Four species of bacteria known to have probiotic effect against known fish pathogens were obtained from the American Type Culture Collection (ATCC): Carnobacterium piscicola, Wessella hellencia, Lactobacillus alimentarius, and Vibrio alginolyticus were evaluated to establish a positive control. Three pathogens, Aeromonas hydrophila, Aeromonas salmonicida, and Listonella anquillarum (formerly Vibrio anquillarum) were used as target organisms. Of the techniques for evaluating the potential of a bacterial isolate as a probiotic, the most effective was an agar well technique. Seven wells were made into an agar plate poured with a pathogen inoculum, six wells were filled with a potential probiotic and the seventh is filled with sterile saline. A clear measurable zone of inhibition occurred around wells of W. hellencia against A. salmonicida. This was used as the positive control when screening the isolates from the snapper and larval culture water. Of the 62 bacteria screened with this method only three isolates showed consistent clear zones of inhibition against Vibiro sp. These three isolates were mass cultured and inoculated into larval tanks prior to stocking larvae. The bacterial loads for each tank were measured for the first four days of each culture period on three different agar types: Marine Agar Difco, Phenyl Ethanol Agar Difco, and TCBS Agar Difco. The bacterial densities ranged from 10 to 109 CFU/mL, and each day had a large degree of variation within the bacterial counts. There was no determined probiotic effect, of three culture trials. Only one trial had any survival to the end of the culture period.

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