Efficacy of a commercial probiotic relative to oxytetracycline as Gram-negative bacterial control agents in a rotifer (Brachionus plicatilis) batch culture

Authors: ROTMAN, FEDERICO - University Of Miami; Riche, Martin; VAN WYK, PETER - Scientific Associates Llc; BENETTI, DANIEL - University Of Miami

Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2011
Publication Date: 8/28/2011
Citation: Rotman, F.J., Riche, M.A., Van Wyk, P., Benetti, D.D. 2011. Efficacy of a commercial probiotic relative to oxytetracycline as Gram-negative bacterial control agents in a rotifer (Brachionus plicatilis) batch culture. North American Journal of Aquaculture. 73:343-349.

Interpretive Summary: Rotifers are an important live feed organism for marine larval fish. However, rotifer cultures can carry pathogenic bacteria. Two trials, one with an initial low rotifer density and one with an initial high rotifer density were conducted to evaluate two microbial control strategies in rotifer cultures. Rotifers were reared in the presence of the antibiotic oxytetracycline or a commercial probiotic to determine the efficacy of each for reducing pathogenic bacteria and enhancing population growth and reproduction. Oxytetracycline was an effective antimicrobial and enhanced rotifer production at high rotifer densities, but only had a marginal effect on production at low rotifer densities. Conversely, the low rotifer density culture with the probiotic had no effect on rotifer production. Inoculation of the high rotifer density culture had an adverse effect on rotifer production and reproduction. Utilization of probiotics in rotifer cultures to reduce the potential introduction of pathogenic bacteria into larval culture systems is not as effecious as oxytetracycline, and utilization of high doeses may adversely affect the rotifer culture.

Technical Abstract: Two trials were conducted to evaluate two gram-negative bacterial control strategies in batch cultures of the rotifer Brachionus plicatilis. In the first trial, rotifers at an initial density of 47/mL were cultured for 5 d and dosed with a 10-mg/L solution of either oxytetracycline or a commercial probiotic consisting principally of Bacillus and Lactobacillus. In the second trial, rotifers at an initial density of 140/mL were cultured for 4 d and dosed with 20-mg/L solutions of oxytetracycline or the probiotic. Rotifer density, egg counts, and egg : female ratios were determined daily. At the termination of trial 1 and on days 0, 2, and 4 of trial 2, counts of bacterial colonies were conducted to estimate bacterial loads in the rotifer culture water. Oxytetracycline was an effective antimicrobial and enhanced rotifer production in the higher-density culture but had only a marginal effect on production in the lower-density culture. Conversely, inoculation of the low-density culture with the probiotic had no effect on rotifer production. Inoculation of the high-density culture adversely affected rotifer production by increasing mortality and reproductive inhibition.