Abstract: A bacterial strain named as strain G0503 was isolated from the mucus of ophthalmitis turtleTrachemysscriptaelegans(body weight of 150.0 g), and the morphological observation, physiological and biochemical characteristics, and sequencing of 16S rDNA and phylogenetic tree analysis were carried out in this study. Results showed that the G0503 strain was a rod-shaped, and gram-negative bacillus, and was characterized by production of acid from mannose, galactose and inositol, and negative reaction for lysine and ornithine decarboxylase. Furthermore, the 16S rDNA sequences was amplified by PCR method, and subcloned into pMD18-T vector, with a sequencing product of 1500 bp in length. The 16S rDNA sequence had a 99.30% similarity withProvidenciarettgeritype strain DSM 4542(AM040492.1), and clustered into one group withProvidenciarettgeri(JN644501.1), indicating that the G0503 strain was identified asP.rettgeri. The antibiotic susceptibility test showed that it was sensitive to cefoperazone, cefotaxime, levofloxacin, norfloxacin and florfenicol, and resistant to amoxicillin, ampicillin, sulfamethoxazole, sulfamethoxazole and trimethoprim. The challenge test revealed that the isolate resulted in mortality rate of 40% of the diseased turtle, with clinical signs including asthe swollen, increase in mucus of eye and feeding stop, which were consistent with the natural symptoms of the diseased turtles. Histopathological observation showed that reduction in the epithelium cell number and increase in chromatophores in the eyes. The findings firstly reported the isolation and identification ofP.rettgerifrom the turtle with ophthalmia, and will provide scientific reference for prevention and treatment in fish.
2018, Vol. 33 
