Detection Of Several Important Bacterial Pathogens Of Channel Catfish In Sichuan And Studies On Characteristics Of Pathogens

Since 1984 introduced in China, channel catfish was now extended to more than 30 provinces and cities, including Hunan, Hubei, Jiangxi, Anhui and Guangdong etc. And in some provinces and cities, they had formed considerable scale farming. Meanwhile, as a province which had a large scale channel catfish farming, and annual output of channel catfish in Sichuan gradually increased. However, in recent years, with the expansion of farming area, stocking density increased and a number of regional aquaculture water environment deteriorated, decline in the quality of farmed species and drug abuse, massive diseases of channel catfish had broken out in Sichuan Province, which resulted in huge economic losses. In order to understand the pathogen species of bacterial diseases of channel catfish in Sichuan, accurate identification and monitoring of common pathogeny,we studied bacterial diseases of channel catfish naturally occurred in City Meishan, Deyang, Mianyang and Jianyang of Sichuan Province from 2007 to 2008,which could establish a foundation for preventing and controlling channel catfish diseases.Phenotypic informations of isolates were identified, including isolation and pure culture of isolates, detection of morphological and colonial characteristics, detection of physiological and biochemical characteristics. In addition, molecular identification of analysis of the nucleotide sequence of the 16S rDNA gene was applied, the 16S rDNA genes were sequenced and the phylogenetic tree representing genetic relatedness among the isolates and publicly available 16S rDNA gene sequence from GenBank database was constructed.We examined the cases of bacterial diseases in this study, including season of disease, susceptible fish weight, morbidities and mortalities. The results showed that these important bacterial pathogens were A. veronii,A. hydrophila,S. maltophilia and Y. ruckeri. And the results showed that pathogens of important bacterial diseases in Meishan, Deyang and Jianyang were A. veronii,A. hydrophila and S. maltophilia; except for A. veronii and A. hydrophila, Y. ruckeri was also the pathogen of important bacterial diseases in Mianyang, which was first isolated from channel catfish in China.The important bacterial diseases of channel catfish could occur through out the breeding process, but diseases occurred more from March to October every year.Antimicrobial susceptibilities of isolates to antimicrobial agents were determined, and the results showed resistant scope of isolates. The isolates caused different bacteriosis were sensitivity to different drugs. A. veronii was sensitivity to florfenicol, norfloxacin, Ciprofloxacin, tetracycline and doxycycline. A. hydrophila was sensitivity to florfenicol, norfloxacin, Ciprofloxacin, deoxycycline, amikacin sulphate and neomycin. S. maltophilia was sensitivity to florfenicol, norfloxacin, Ciprofloxacin, deoxycycline, Sulfamethoxazole and Sulfamethoxazole B. Y. rucker was sensitivity to florfenicol, norfloxacin, Ciprofloxacin, doxycycline and kanamycin.