Experimental pathogenesis of Flavobacterium columnare in channel catfish (Ictalurus punctatus) and characterization of selected isolates

Three isolates of yellow bacteria from diseased channel catfish and the ATCC isolate #23463 from diseased Chinook salmon were confirmed to be Flavobacterium columnare based on basic characteristics described by Griffin.; Subsequent to a spontaneous outbreak of Columnaris disease in yearling channel catfish after transportation to the Aquarium room at the Clemson University Fish Health Laboratory, an experiment was conducted to investigate the control and progress of the disease. The potassium permanganate treatment did not protect catfish from infection, which resulted in a dramatic mortality rate of between 88--92% within 4 days. Although the Oxytetracycline treatment of the clinical group had a higher mortality rate (26%) than prophylactic treatment regimen (0%), the primary immune response was still detected in the surviving catfish.; To investigate the route of entry of F. columnare in fish, an infectivity experiment was conducted on randomly chosen fish placed in eight groups of six replicate groups of 10 fish each. The treatments were divided into a control group, 4 groups infected via internal routes, and 3 groups via external routes. The internal routes involved the inoculums of fish with the Clemson isolate by intramuscularly injection (IM), intraperitoneal injection (IP), oral and anal gavages administration.; To identify the outer membrane proteins (OMPs) of isolates of F. columnare, they were isolated with the N-lauryl sarcosine extraction and analyzed using SDS-PAGE. Two OMP patterns were observed upon SDS-PAGE using the ATCC isolate from diseased Chinook salmon and 6 isolates from diseased channel catfish. Outer membrane protein molecular weights ranged from 117.2 KDa to 21 KDa. A 30 KDa protein was missing from the ATCC isolate and the 40 and 26 KDa proteins were exhibited as major proteins. These results suggest a possible advantage ATCC 40 KDa for immunodiagnostic genus identification. On the other hand, the mouse PAb anti-30 KDa OMP for the Clemson isolate only reacted to the 30 KDa protein of the Clemson, Auburn, and South Carolina, confirming the lack of 30 KDa protein in the ATCC OMPs. As a result, the PAb anti-30 KDa could possibly be employed for serotyping among F. columnare isolates. (Abstract shortened by UMI.)...