Identification and Pathogenicity of Pseudomonas aeruginosa DJ1990 on Tail and Fin Rot Disease in Spotted Snakehead

Tail and fin rot disease (TFRD) is a big issue in the production of spotted snakehead, Channa punctata Bloch. The aims of the present study were to isolate and identify the bacterial pathogen causing TFRD, to detect histopathological changes in tissues (fin, tail, liver, and kidney), and to ascertain the antibiotic sensitivity pattern of the isolate. Out of six bacterial isolates, only the isolate DJ1990 was found to be the causal candidate of TFRD in C. punctata. Identical histopathological changes were detected in tail, fin, liver, and kidney under light and scanning electron microscope in both collected diseased fish and artificially infected fish. The isolate was identified as Pseudomonas aeruginosa strain DJ1990 (National Center for Biotechnology Information Ace. No. KX709967) based on the biochemical characterization tests and 16S rDNA sequence-based phylogeny analysis. Artificial challenge test demonstrated that the strain DJ1990 was highly virulent (100% mortality at 48 h of postinjection period at the concentration of 1.5 × 107 CFU/g of body weight) for C. punctata. The isolate exhibited sensitivity to the broad-spectrum antibiotics but was resistant against aztreonum. To the best of our knowledge, this is the first report of P. aeruginosa as a TFRD-causing candidate in C. punctata.