This study was conducted from 1/2010 to 12/2013 and identifed Shewanella gelidimanna which is a causative agent of the ulcerative disease in Bagarius rotilus in Vietnam. The isolation of this bacteria from fish was observed the highest from July to September, especially in August with the prevalence of 35 percent. The lowest prevalence was observed in the duration from January to March (2.5 percent)
from April to June and October to December, the prevalence were 5 and 10 percent, respectively. Shewanella gelidimarina was the most susceptibility to Enzofloxaxin, extracts of garlic (Allium sativum L) and pressed leaves bop bop (Chromolanea odorata), rifamixin and tetracycline. However, the bacteria was resistant not to ampicillin.