Maximum parsimony tree of E. coli O157:H7. Comparison of 70 genomes yielded a total of 3313 SNPs of which 1266 were parsimony informative. The tree shown is a majority-consensus tree of 28 equally parsimonious trees with a consistency index of 0.998. Trees were recovered using a heuristic search in Paup 4.0b10 (Wilgenbusch and Swofford, 2003). Only nodes with bootstrap values below 100 are listed. Phylogenetic clade association is provided in circled numbers (Manning et al., 2006). Strains investigated are comprised of PM, Plate mates; IH, intrahousehold infections; BL, Battle Ground Lake; CD, Cookie Dough; FS, Finley School District; FF, Fairbank Farms; TB, Taco Bell; TJ, Taco John; and TP, Totino's Pizza. Our plasmid survey confirmed that all strains carry the lineage-specific plasmid pO157. Further we identified other plasmids with a size range from 34 to 78 kb. Plasmid type prevalence is represented in colored circles: p78 (yellow), p63 (orange), p55 (light brown), p39 (red), p36 (brown), p34 (dark brown), and a small 3.3 kb plasmid (black) (Makino et al., 1998). Plasmid p36 is homologous to pEC4115 (Eppinger et al., 2011b).