Tadatoshi Kitao

Protective efficacy ofAeromonas hydrophila vaccines in Nile tilapia

Protection and serum antibody production against Aeromonas hydrophila was examined in nile tilapia, Tilapia nilotica (L.). Intraperitoneally injected formal in-killed and Freunds complete adjuvant vaccines were compared using different doses (2.9 X 10(7) and 2.9 X 10(9) cfu/ml). Upon challenge, the protective ability and antibody titers resulting were significantly different between vaccinated and unvaccinated groups. A relative level of protection of 100% was obtained within two-weeks, and a maximum level of 53-61% protection was found one-week post-vaccination.

Immunomodulatory effects of the fermented products of chicken egg, EF203, on rainbow trout, Oncorhynchus mykiss

Abstract Immunomodulatory effects of immunoactive peptides from the fermented products of chicken egg (EF203) administered orally to rainbow trout, Oncorhynchus mykiss , were investigated. The chemiluminescent responses of kidney phagocytes after treatment with EF203 were significantly increased. Fish administered EF203 showed high phagocytic activities as compared to controls, and immunomodulatory effects were found to be dose dependent. Fish treated with EF203 displayed an increased resistance to both natural and experimental beta-haemolytic streptococcal infection.

Drug resistance and R plasmids in Vibrio anguillarum isolated in cultured ayu (Plecoglossus altivelis).

Two hundred twenty‐six strains of Vibrio anguillarum collected from cultured ayu (Plecoglossus altivelis) between 1978 and 1980 were studied for their sensitivities to 10 chemotherapeutics. In order to determine whether the drug‐resistant strains possessed transferable R plasmids, they were conjugated with Escherichia coli. Almost all the strains isolated during the 3 years showed resistance to nalidixic acid (NA) and/or furazolidone (NF). NA and NF resistance were not transferred to Escherichia coli from any of the strains. Chloramphenicol‐resistant strains were isolated in every year and almost all of them carried transferable R plasmids. Only one strain with tetracycline resistance was found among the strains tested. Strains resistant to sulfonamides, streptomycin, ampicillin (ABP), and trimethoprim (TMP) increased rapidly in 1980, and a large number of them carried transferable R plasmids.

In Vitro Antimicrobial Activity of Pyridonecarboxylic Acids against Fish Pathogens

Abstract New pyridonecarboxylic acids (PCAs) were evaluated for in vitro antibacterial activity against Pasteurella piscicida, Vibrio anguillarum, Edwardsiella tarda, and Streptococcus sp., which were pathogens isolated from diseased fish in Japan. The minimal inhibitory concentrations of 11 PCAs, nalidixic acid, oxolinic acid, piromidic acid, pipemidic acid, miloxacin, flumequine, enoxacin, ofloxacin, norfloxacin, ciprofloxacin, and FR77040, were determined with the serial twofold agar dilution method. Newer PCAs, enoxacin, ofloxacin, norfloxacin, ciprofloxacin, and FR77040, showed the strongest antibacterial activity against all the fish pathogens. Oxolinic acid, miloxacin, and flumequine were highly active against the tested fish pathogens except Streptococcus sp. The remaining PCAs, nalidixic, piromidic, and pipemidic acids, were also effective against gram-negative pathogens, but the level of activity was even lower than that of the previous three. The frequency of spontaneous mutation of the pathoge...

Isolation and Classification of a Nocardia species from Diseased Giant Gourami Osphronemus goramy

Abstract An enzootic caused by bacteria occurred among cultured giant gourami in two freshwater fish farms in Kagoshima, Japan, in 1982. Typical external characteristics of the diseased fish were sloughed scales, exophthalmia, and opaque eyes. Internally, numerous creamy white nodules were found in the gills, spleen, kidney, and liver and a lesser number in the bladder and stomach. Nocardia sp. was isolated from spleen and kidney tissues of all diseased fish examined. To clarify the taxonomic position of the isolates, 164 tests were performed, and results were compared to reference strains of six species of Nocardia and one species of Rhodococcus. The isolates formed a homogenous group in a single taxon at a similarity of 98.7% based on an average linkage analysis and were clearly separated from the reference strains. The isolated strains were more similar to Nocardia kampachi than to the other representative species. However, 12 distinct differences were found between the isolates and N. kampachi, includ...

Elimination of challenge bacteria from the blood and intestines of ayu Plecoglossus altivelis vaccinated by immersion

Ayu Plecoglossus alaivelis were immersed for 3 min in a 5% NaCl solution containing 1% lyophilized formalin-killed Vibrio anguillarurm. Two months after vaccination, each of the four experimental groups vaccinated fish were infected by intraperitoneal (i.p) injection of either 103, 104, or 106 cells of V. anguillarum PT479 streptomycin resistant (Smr)-strain or exposed to 106 cells/ml of PT479 Smr strain. The time period of elimination of the infecting organism depended on the number of cells of V. anguillarum given to the fish. The challenge organisms wera virtually eliminated within 6h after i.p. injection of 103 or 104 PT479 Smr cells in the blood and intestinal tracts. On the other hand, organisms increased 12h after injection of 103 or 104 cells/ml in non-vaccinated fish, reaching 106 cells/ml of blood and 105 cells/g in the intestinal tracts by 72h. The challenge organisms were observed in the blood and intestinal tracts of vaccinated fish Within 24h after i.p. injection of 106 cells. Subscquentry, the organisms decreased to 10 cells or less. The number of organisms increased in non-vaccinated fish after i.p. injection of 106 cells. The number of challenge organisms was 10 cells/ml or g, or less, in the blood and the intestinal tracts of vaccinated fish 72h after exposure to 106 cells. The challenge organisms were also ob-served in the blood of non-vaccinated fish for 72h.