Highly pathogenic clone of Shiga toxin–producing Escherichia coli O157:H7, England and Wales

Byrne, Lisa
Dallman, Timothy J.
Adams, Natalie
Mikhail, Amy F. W.
McCarthy, Noel D.
Jenkins, Claire

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Publication date

December 2018

DOI

10.3201/eid2412.180409

Publisher

Centers for Disease Control and Prevention (CDC)

Abstract

We used whole-genome sequencing to investigate the evolutionary context of an emerging highly pathogenic strain of Shiga toxin–producing Escherichia coli (STEC) O157:H7 in England and Wales. A timed phylogeny of sublineage IIb revealed that the emerging clone evolved from a STEC O157:H7 stx-negative ancestor ≈10 years ago after acquisition of a bacteriophage encoding Shiga toxin (stx) 2a, which in turn had evolved from a stx2c progenitor ≈20 years ago. Infection with the stx2a clone was a significant risk factor for bloody diarrhea (OR 4.61, 95% CI 2.24–9.48; p<0.001), compared with infection with other strains within sublineage IIb. Clinical symptoms of cases infected with sublineage IIb stx2c and stx-negative clones were comparable, despi...