FIG. 2.

(a) Neighbor-joining tree reconstructed from the concatenated sequences of each unique ST observed in the pooled data set. The Kimura two-parameter distance measure was used as implemented in MEGA 4.0. The analysis resolved the STs in the two main groups identified previously; group 2 is supported by a bootstrap score of 98. Two STs did not cluster within the two major groups. One of these, ST1223, is omitted for the sake of clarity, while ST152 (corresponding to a single French isolate) is approximately equidistant from the two main groups. The use of ST152 as an outgroup confirms that group 1 is basal to group 2. (b) Neighbor-joining tree showing the divergent position of ST1223. Groups 1 and 2 are collapsed for the sake of clarity, and ST1223 is ∼10% diverged from these groups. Bootstrap scores for the group 2 node and the ancestral node of groups 1 and 2 are given.