Edwardsiella ictaluri sp. nov., the Causative Agent of Enteric Septicemia of Catfish

Abstract

We characterized 13 cultures of the enteric bacterium causing enteric septicemia of catfish by studying their biochemical reactions, deoxyribonucleic hybridizations, and deoxyribonucleic acid guanine-plus-cytosine contents. We confirmed that this bacterium is a new species, which is most closely related to Edwardsiella tarda of the family Enterobacteriaceae. Five strains of the bacterium causing enteric septicemia of catfish were 80% or more related to the type strain, SECFDL GA 77–52 (= CDC 1976–78 = ATCC 33202), in 60°C deoxyribonucleic acid homology reactions. Species level relatedness among the 13 strains which we studied was demonstrated by the more than 80% relatedness in 75°C reactions. The bacterium causing enteric septicemia of catfish was most closely related to E. tarda (56 to 62%) in 60°C reactions. The guanine-plus-cytosine was 53 mol%, as determined by buoyant density centrifugation. We propose the name Edwardsiella ictaluri sp. nov. for the bacterium causing enteric septicemia of catfish.