Figure 2

Neighbor-joining phylogeny based on seven multilocus sequence typing loci (3738 bp) among non-O157 Shiga toxin-producing Escherichia coli isolates from Michigan, 2001–2018. The nodes at each branch represent the support percentages after bootstrapping (1000 replicates). The Maximum Composite Likelihood method was used to calculate the evolutionary distances (number of base substitutions per site). Three clades were identified that clustered together with > 70% bootstrap support, while seven subclades, A-G, are shown within clade I. Sequence types (STs) are noted at the end of each branch followed by the serogroup and number (n) of isolates per serogroup. The big six serogroups and a set of additional serogroups that were found on multiple branches of the phylogeny are represented by different colored circles. The frequency of Shiga toxin (stx) genes per subclade and clade is shown in the pie charts with different colors representing the three toxin gene profiles.