Study on isolation and some pathological characteristics of Flavobacterium columnare causing infection in tilapia (Oreochromis spp.) cultured in Northern Vietnam

The study aims to isolate, identify, and determine the pathological characteristics of Flavobacteria columnarecausing disease in tilapia cultured Northern Vietnam. A total 138 samples suspected being infected with F. columnare were collected from 34 outbreaks at 21 farms Hoa Binh, Ha Nam, Hai Duong provinces. results showed that exhibited typical symptoms such as fibrous, silver gills, appearance silvery white spots on skin, fibrous fins. can occurr anytime, but focusing much damage winter-spring crop accumulative mortality rates 5-35%. 87 isolates retrieved fish samples; representative (1 isolate per outbreak) successfully identified by phenotypic, biochemical tests, PCR assays. Using TYES medium, grew yellow rhizoid colonies after 36-48 h culture. bacteria gram-negative, long filamentous, absorbed Congo red dye, produced flexirubin pigment, gliding motility, positive catalase oxidase tests. well a temperature 25-28°C, pH 7-8 NaCl concentration below 5‰. present provide critical information developing strategies for prevention control infection tilapia.