Isolation, identification of a pathogenic Morganella morganii from ornamental koi(Cyprinus carpio koi)

A bacterial isolate of A400502 was isolated from Cyprinus carpio suffered from severe muscle ulceration in a fish farm of Shandong province in 2009. The artificial infection proved that the isolate A400502 was the pathogen of the disease. The isolate A400502 was typical bacteria of Gram-negative rods(0.5 μm-0.7 μm×1.0 μm-1.5 μm). The biochemical characterizations of the isolate were determined by ATB expression and the results showed that positive reactions were observed on ornithine decarboxylase(ODC), urease(URE) and phenol red(PR). Analysis of 16S rDNA sequence showed that the isolate shared more than 99% identity with Morganella morganii. Based on the morphological, biochemical and phylogenetic analysis, the isolates A400502 was identified as M.morganii. The antibiotic sensitivity test indicated that the pathogenic isolate showed high sensitivity to 11 of 26 antibiotics, such as ceftazidime, gentamicin, neomycin, etc.