Studies were made on tissue levels of ampicillin(Amp)in cultured yellowtail, Seriola quinqueradiata which were given 40 mg of Amp per kilogram of body weight. The fish were fed the drug-containing food once a day for successive 5 days prior to the drug analysis. The water temperature was 23.2 to 25.4°C, average 24.2°C, during the course of experiment. The highest tissue level of Amp was obtained 1 hour after medication in liver and 3 hours in kidney. The highest level of Amp was found in liver and the lowest level was in muscle.The levels of Amp in those tissue became almost undetectable after 48 hours.
The serological relationship between of causative organism of bacterial pseudotuberculosis in yellowtail, Seriola quinqueradiata, and Pasteurella piscicida JANSSEN and SURGALLA (1968) was investigated by Ouchterlony method and immunoelectrophoresis. Since the organisms isolated from cultured yellowtail in various places in Japan showed the similar immunodiffusion pattern, they were concluded to be the same serotype. The organism posesses one heat stable and four heat labile antigens in whole packed cells and three heat labile extracellular antigens. The immunodiffusion pattern of the organisms coincided with that of P. piscicida. Therefore it will support authors' previous result that the organism was identified as P. piscicida with the biological and biochemical characteristics. There was no taxonomical analogue strain investigated that cross-reacted with the causative organism except the strain Pasteurella plecoglosacida strain TA-IIK. TA-IIK isolated from ayu, Plecoglossus altivelis, produced one common precipitin line and spur.
Experiments on the effect of dilution of fish meat extract in the FME agar on the growth of MG-fungus revealed that the fungus grew best on the FME agar which consisted of 10% w/v fish meat extract plus 1.5% Difco agar. The MG-fungus grew well on the FME agar at 15 to 30°C, but failed to grow at 5 and 37°C. It grew in the FME broth at the pH range 5 to 10. Chloramphenicol, malachite green, cycloheximide and NaCl completely inhibited mycelial growth at concentrations of 100 ppm, 1.0 ppm, 0.4 ppm and 1.0%, respectively. The mycelium of MG-fungus was killed in 10 ppm cycloheximide solution and 2% NaCl within 24 hours and 0.5 ppm malachite green solution within 2 hours.
The experiment was designed to examine the application of trimethoprim (TMP) and sulfonamides (SA) as therapeutical agents for vibriosis in ayu, Plecoglossus altivelis. Microbiological evaluation was made for TMP and SA in alone and combined on the causative agent Vibrio anguillarum in comparison with some known chemotherapeutic agents. Antimicrobial activity in vitro and therapeutical effect in vivo were also observed for ayu infected experimentally and naturally. Results obtained are following: 1. In the antimicrobial activity, TMP was superior to other drugs, chloramphenicol, tetracycline, nitrofurazone and nalidixic acid against drug-resistant V. anguillarum strains. Synergism of TMP and SA was clearly obtain on SA-sensitive strains in vitro. 2. V. anguillarum growing in broth containing the rising concentration of TMP-SA increased resistance in 2 to 8-fold after 10 transfers, even in the strains of SA-sensitive. 3. Therapeutic effect of TMP on the diseased fish; TMP was effective on vibriosis which was caused experimentally and naturally by the drug-resistant strain of V. anguillarum.
Infection tests were attempted to clarify various conditions which precipitated diseases of young red seabreams. Vibrio alginolyticus CY-1 isolated from diseased fish in 1975 was used for the tests. Young red seabreams showed signs of disease both in the water containing V. alginolyticus and in the one with the bacteria and Rotifera. Higher mortality occurred in the latter case. Red seabreams reared in the seawater with the bacteria and Chlorella had a higher surviving rate than those in the seawater without Chlorella. It was observed through other experiments that V. alginolyticus in the sea water with both Rotifera and Chlorella tended to increase in number as the number of Chlorella was decreased by the consumption of Rotifera.
An immunodiffusion test with heat stable antigen extracted from the kidney of infected fish is described as a method of diagnosis of BKD. Specific precipitin bands were formed within 24 hours when the rabbit anti-serum reacted with the extract of affected parts of the kidney containing heat stable specific BKD antigen. No precipitin bands were formed with heat extract of the kidney of healthy fish and heat extract of cells of other fish pathogenic bacteria, i. e. Aeromonas salmonicida, Vibrio anguillarum, etc. From the above findings, it was suggested that the correct diagnosis of BKD could be easily made in distant diagnostic laboratory by the sending of heat treated field specimens.
Several kinds of insecticides have been applied in eel ponds in Japan to eliminate unfavorable zooplanktons for fish. Among these organisms, Ostracoda (Crustacea) is strongly resistant to the chemicals so far adopted. In the present study, methyl isoxathion, a new organo-phosphorous compound developed by Sankyo Co., was confirmed to be highly effective against the Ostracoda, Candonocypris assimilis SARS, 1895 and Heterocypris incongruens (RAMDOHR, 1808) subsp. attenuata (GAUTHIER, 1938), when applied in the water. A 50% emulsion of the compound killed the pests in clean water at levels of 0.1 to 0.2 ppm during 3 days at room temperature, but the effectiveness of the chemical was found to reduce at a low temperature and by the concomitance of phytoplankton and/ or the mud. The drug was not harmful to the young fishes of Anguilla anguilla, A. japonica, Carassius auratus and Cyprinus carpio, at concentrations below 2.5 ppm of the emulsion.