| Summary |
During the months of March and April of 1996, about four to five hundreds of rainbow trout died in an aquacultrue pond, about one hectare in size and cultured 120 - 130 thousands of rainbow trouts, located in the northern part of Taiwan. The symptoms on the outlooks were hemorrhaged eyeballs with ulcer in the surrounding areas. Autopical examinations found degenerated liver color, enlargement of bile bladder, dark spleen, and kidney enlargement and darkness. The isolated bacteria were cultured with blood agar, brain heart infusion agar, tryptic soy agar, and SS agar. They grew in the first three media at 25 °C and 37 °C but not at 45 °C . On the contrary, the bacteria did not growth in SS agar at all under the three different temperature conditions. The colonies on brain heart infusion agar were uniform in size and appeared with milk white color. They showed no hemolysis on blood agar culture. Gram were positive by 3 % KOH examination; catalase and oxidase tests were all negative. In light microscope examination, they appeared like bicoccus or short chain and did not have a flagellum. Additional observations by electron microscope found pili-like substance. According to the API 32 Strept tests, Lactococcus garvieae was identified. When pathogenicity tests using mice and Cyprinus carpio were conducted, the bacteria could not cause mortality in either case. The antibiotic sensitivity tests performed revealed that the bacteria were more sensitive to ampicillin and erythromycin than amikacin, chloramphenicol, chlortetracycline, lincomycin, gentamicin, rifampicin, tetracycline, trimethoprim, nalidixic acid, nitrofurantoin, kanamycin, oxytetracycline and streptomycin. This is the frist report of the Lactococcus garvieae isolated from rainbow trout in Taiwan.
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| Keyword |
Rainbow trout, Hemorrhage, Lactococcus garvieae, Ampicillin, Amoxicillin.
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