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| Isolation,Identification and Pathogenicity of a Pathogenic Bacterium from Largefin Longbarbel Catfish,Mystus macropterus Bleeker |
| LI Chun-tao,YANG Xiu-ying,JIANG Zi-li |
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Abstract Bacterial pathogen strain MM-A was isolated from largefin longbarbel catfish ( Mystus macropterus) , suffered from a kind of disease with typical head-ulcerative symptom . The bacterial pathogen strain MM-A was confirmed to be the causative agent of the epidemic by artificial infection test and the LD50 was about 5 .3 × 107 cfu/mL .According to physiological feature ,biochemical indexes and 16s rDNA sequence ,the MM-A was further proved to be Edwardsiella ictaluri .The comparison of 16S rDNA molecule in Enterobacteriaceae showed that the strain MM-A shared the highest level of similarity (99 .4% ) with that of the E .ictaluri ,and they had the same position in the molecular phylogenetic tree based on 16S rDNA sequence in Enterobacteriaceae .The drug susceptibility test revealed that the isolated strain MM-A was susceptible to oxyteracycline ,streptomicinum ,ofloxacin and other antibiotics ,lowly susceptible to tetracycline and other antibiotics and Chinese medicinal herbs including Terminalia chebula , and Fraxinus rhynchophylla .
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Received: 25 March 2014
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