Phylogenetic analysis of stx gene PCR product of total DNA. The DNAPARS DNA parsimony program was used to generate the phylogenetic trees of the representative stx PCR product sequences . The bootstrap method with 1000 replicates, 2822 steps, at 1278 sites was performed. The consensus tree is shown. The three canine fecal bacterial isolate groups are indicated by the gray boxes. GenBank accession numbers are indicated in parentheses.