Figure 2

Neighbor-joining tree based on nucleotide variation at 7 conserved housekeeping loci. The partial gene sequences for 7 housekeeping loci of CTEC-II strains Sw-9 and AH-5, E. coli, E. fergusonii and E. albertii were concatenated in the order adk, fumC, gyrB, icd, mdh, purA and recA and aligned. Based on 3,423 bp of the concatenated sequences, a neighbor-joining tree was constructed by using MEGA 4 software.