Genomic subtyping of Edwardsiella ictaluri isolated from diseased channel catfish by arbitrarily primed polymerase chain reaction

Arbitrarily primed polymerase chain reaction (AP-PCR) combined with an enterobacterial repetitive intergenic consensus PCR primer (ERIC II) was used to genomically subtype 20 isolates of Edwardsiella ictaluri. Nineteen isolates were derived from channel catfish Ictalurus, us punctatus (18 from the southeastern United States and an American Type Culture Collection reference strain), and 1 isolate was derived from a walking catfish Clarias batrachus from Thailand. From these isolates, four major subgroupings of E. ictaluri were observed. These subgroups were distributed with the following prevalences: subgroup 1, 55%; subgroup 4, 20%; subgroup 2, 15%; and subgroup 3. 10%. Biochemical analysis showed homogeneity among isolates and was not useful for discriminating between isolates.