Studies On The Vibriosis Of Large Yellow Croaker (Pseudosciaena Crocea) And Control Coutermeasures Of Hte Disease

From May to August in 2000, in Xiangshang Bay, Ningbo, Zhejiang province, the net-cage cultured large yellow croaker (Pseudosciaena croced) occurred infection diseases, the infected fish showed two types of main symptoms: one type, the skin festered and the caudal fin rotted; the other type, the infected fish was anorexia, it's stomach and intestine were empty, and the end intestine was full of yellow mucus. Five strains were isolated from the liver, kidney and spleen of the infected fish. Four of them were proved to be the causative agent after artificial infection. The five strains showed the morphological, physiological, and biochemical characteristics of the genus Vibrio. And according to the results of over 40 tests, comparison to the data of Bergey's Manual of Determinative Bacteriology (9th, edition), 2 and 3 strains seemingly belong to two different species, Vibrio harveyi and Vibrio parahaemolyticus, respectively.In vitro, efficacies of antibiotics were tested on pathogenic bacteria fromPseudosciaena crocea infected with vibriosis--Vibrio harveyi (the strainY62001 and Y80721) and Vibrio parahaemolyticus (the strain Y70301, Y70701and Y80704 ). Twelve antibiotics, namely, Ciprofloxacin , Norfloxacin , Ampicillin , Tetracycline , Streptomycin , Neomycin , Chloramphenicol, Midecamycin, Spiramychin, Cyadox, Oxolinic arid, Cephalexin were studied. The efficacies of the antibiotics on five strains were determined as well as minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC). The two strains showed high susceptibilities to Ciprofloxacin and Norfloxacin, while the two strains showed low susceptibilities to the other ten antibiotics. It was showed that Ciprofloxacinand Norfloxacin exhibited chemotherapeutic effects on Pseudosciaena crocea infected with vibriosis when it was orally administered (5.0 g/g, once a day for three days).Formalin and phenol and heat killed cells of Vibrio harveyi were prepared to show immunogenicity to Caressius auratus gibel by examination of agglutinating antibody litres of serum as well as phagocytic activity of blood leucocytes. It was proved that three bacterins mady by three methods showing strong immunogenicity and formalin-killed V. harveyi showed the strongest immunogenicity among three bacterial preparations and phenol-killed V. harveyi showed stonger immunogenicity than heat-killed V. harveyi.