Atypical Shigella boydii 13 encodes virulence factors seen in attaching and effacing Escherichia coli.

Enterohemorrhagic Escherichia coli (EHEC) is a foodborne pathogen that causes watery diarrhea and hemorrhagic colitis. In this study, we identified StcE, a secreted zinc metalloprotease that contributes to intimate adherence of EHEC to host cells, in culture supernatants of atypical Shigella boydii 13 (Shigella B13) strains. Further examination of the Shigella B13 strains revealed that this cluster of pathogens does not invade but forms pedestals on HEp-2 cells similar to EHEC and enteropathogenic E. coli. This study also demonstrates that atypical Shigella B13 strains are more closely related to attaching and effacing E. coli and that their evolution recapitulates the progression from ancestral E. coli to EHEC.