Fish Pathology
Online ISSN : 1881-7335
Print ISSN : 0388-788X
ISSN-L : 0388-788X
Effects of Sodium Nifurstyrenate and Tetracycline on the Bacterial Flora of Rotifers (Brachionus plicatilis)
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1989 Volume 24 Issue 1 Pages 29-35


The effects of sodium nifurstyrenate (NFS-Na) and tetracycline (TC) on the aerobic bacterial flora of rotifers (Brachionus plicatilis) were evaluated both in vivo and in vitro.
In vivo, the bacterial numbers on ZoBell's 2216e agar of rotifers exposed to 5μg/ml of NFS-Na decreased slightly, but the numbers on BTB teepol agar rapidly declined from 107 to 105 CFU/g after 5 h exposure. At the same time, a decrease in the incidence of Vibrio accompanied by an increase of Moraxella or Acinetobacter was observed in the NFS-Na medicated rotifers as compared with the controls. The viable counts on the two media and microflora of rotifers exposed to 1 or 5μg/ml of TC exhibited similar pattern to those of the controls throughout the exposure period.
In vitro, 60 strains of bacteria isolated from the rotifers were tested for their susceptibility to the two chemotherapeutics. All the Vibrio strains tested were sensitive to NFS-Na, the MIC values ranging from 0.1 to 1.6μg/ml. The strains of Acinetobacter, Moraxella and Pseudomonas were less susceptible or resistant to the drug. With respect to TC, most of the strains of the four genera were resistant.

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