The Variation in Virulence among Flavobacterium psychrophilum Strains Isolated from Chum Salmon Oncorhynchus keta

Abstract

We investigated virulence and elastindegrading activity in ten strains of Flavobacterium psychrophilum isolated from chum salmon Oncorhynchus keta in Hokkaido, Japan through 2004 to 2006.Intraperitoneal injection of these strains to chum salmon fry revealed that 50% lethal doses (LD50) of the strains were from 2.6 ×015 to .47 ×017 CFU/g.No clear relationship between elastindegrading activity and virulence in these strains was found. These results indicate that the virulence of F. psychrophilum isolated from chum salmon varies considerably among strains, and is not clearly related to elastin-degrading activity © 2013 The Japanese Society of Fish Pathology.