FIG. 2.

Dendrogram showing genetic relationships of 21 C. difficile isolates based on the composite sequence (1,705 bp) of three toxin regulatory genes, tcdC, tcdR, and cdtR. Two A− B+ toxin isolates were not included since their cdtR fragments could not be amplified. The dendrogram was obtained by the neighbor-joining method with the Kimura two-parameter model. Bootstrap values were calculated from 1,000 resamplings of the original data. ST, sequence type number. Alleles for tcdC, tcdR, and cdtR are shown in parentheses. A, animal isolate.