지느러미 부식과 체색변화를 나타내는 틸라피아 병어로부터 분리한 병원균의 성상은 다음과 같다. 1. 병어로부터 분리한 병원균은 Flexibacter clumnaris로 동정되었다. 2. 분리한 병원균액으로 인위감염시켰을 때 전형적인 columnaris병 증상을 나타냈다. 3. 병원균은 kanamycin, tetracycline, amikacin 등에서 높은 감수성을 나타냈으나, sulfa제에서는 거의 감수성을 나타내지 않았다. 4. $2\%$ 이상 식염이나 $50\%$이상 해수를 함유한 cytophaga배지에서 병원균은 자라지 못했다. 5. 증류수 대신 $50\%$ 이상 해수를 함유한 Cytophaga배지에 병원균을 접종시킨 후 1시간만에 약 11에서 $10^6/ml$에서 $10^4ml$로 균수가 감소했는 데 반하여, $5\%$ 이상 식염을 함유한 cytophaga 배지에서는 접종 후 1시간만에 균수가 약 $10^5/ml$에서 10/ml 이하로 급격히 감소했다.
The characteristics of a pathogen isolated from infected tilapia, which showed the external symptoms of fin erosion and body deceleration, were examined. The strain of isolated pathogen was identified as Flexibactor columnaris, The normal tilapia dipped into suspensions of the isolated pathogens has developed the infective symptoms. The strain of Flexibactor columnaris was sensitive to kanamycin, tetracycline, and amikacine, but resistant against sulfa drugs. This strain could not grow in the cytophaga media containing over $2\%$ NaCl or over $50\%$ sea water. In cytophaga broth containing more than $50\%$ or sea water instead of distilled water, the number of Flexibacter columnaris decreased from about $10^6/ml;to;10^4ml$ within one hour after inoculation. On the other hand, in cytorhaga broth containing more than $5\%$ of NaCl, the number rapidely reached less than 10/ml from about $10^5/ml$ within one hour after inoculation.
