The isolation of Edwardsiella ictaluri with a limited tolerance for aerobic growth from channel catfish

While culturing trunk kidneys from channel catfish Ictalurus punctatus with deep ulcerative lesions, we discovered strains of Edwardsiella ictaluri th at could not be isolated under aerobic conditions. After passage of these b acterial isolates in an aerobic environment, minimal growth was observed. I n thioglycolate broth, the passaged isolates had growth characteristics of bacteria with a limited tolerance for oxygen. Isolate S97-133, from May 199 7, was identified as E. ictaluri by the National Veterinary Services Labora tories, Diagnostic Bacteriology Laboratory, Ames, Iowa. The S97-133 isolate and three others from 1994 were also definitively identified as E. ictalur i by the use of the monoclonal immune dot-blot technique. In all, eight iso lates were obtained from channel catfish over an 8-year period. All isolate s were obtained during the months of May, June, July, and November.