ISOLATION, IDENTIFICATION AND PHYLOGENETIC ANALYSIS OF YERSINIA RUCKERI IN CHANNEL CATFISH ICTALUNES PUNCTATUS
斑点叉尾(鱼回)(Ictalunes punctatus)源鲁氏耶尔森氏菌的分离鉴定及系统发育分析

A bacterial strain named FF003 was isolated from the liver and kindey of the diseased channel catfish Ictalunes punctatus. FF003 had apparent pathogenicity to channel catfish. Symptoms in FF003-infected fish included punctate haemorrhaging on the body surface, especially on the submaxilla, abdominal wall and the side of the body. All visceral organs had different degree of hemorrhages; in particular peritoneum and the endomembrane of swim bladder showed punctate hemorrhage. The isolated strain was an aerobic, non-fermentative bacterium. FF003 cells were rod-shaped, Gram negative, Methyl red positive, oxidase negative, and arginine dihydrilase, rnithine decarboxylase and lysine decarboxylase positive. Many carbohydrates could not be utilized by FF003 for acid production, expect maltose, mannose, fructose, trehalose, and D- mannitol. A phylogenetic tree was constructed by comparing with the 16S rDNA sequence of the strain FF003 (GenBank accession number FJ908709) and other relative bacteria species in the GenBank. In the phylogenetic tree FF003 and Yersinia ruckeri constituted a branch. According to morphological, physiological and biochemical characteristics and phylogentic analysis, strain FF003 was identified as Y. ruckeri. Antibiotic sensitivity testing showed that FF003 was very sensitive to norfloxacin, ciprofloxacin, doxycycline and chloramphenicol, but not sensitive to cefradin, clarithromycin, sulfamethoxazole, gentamicin and midecamycin.