The 140 Nile tilapia and 70 Catfish samples were collected from earthen ponds fish farms
and cage culture farm in Moon River in Ubon Ratchathani province during June-November, 2013
and bacterial strains were screened from the skin lesions or yellow areas of Nile tilapia and Catfish
samples on cytophaga agar supplemented with polymycin B and neomycin. Among 36 bacterial
isolates, 9 (from Nile tilapia) and 27 (from Catfish) isolates showed yellow-orange pigmented
colonies, adhering tightly to the agar medium and rhizoid edges, slender and long bacilli. By gram
staining, they were Gram negative and filamentous bacteria. Of the 36 isolates, only one showed
purity and highest growth density in 7 times subculturing, therefore, it was selected and identified
by phenotypic characterization. The selected strain exhibited no growth at 4๐
C little growth at 20๐
C,
optimum growth at 25๐
C and growth at 30
๐
C, colonies appear to be flat, dry, spreading and
strongly adhere to agar medium, yellowish orange color (flexirubin-type), the strain in broth