Heteropathogenic virulence and phylogeny reveal phased pathogenic metamorphosis in Escherichia coli O2:H6

Martina Bielaszewska,Angelika Fruth,Phillip I Tarr,Roswitha Schiller,Lydia Lammers,Barbara Middendorf,M Alexander Schmidt,Helge Karch,Alexander Mellmann,Ulrich Dobrindt,Andreas Bauwens

doi:10.1002/emmm.201303133

Abstract

Extraintestinal pathogenic and intestinal pathogenic (diarrheagenic) Escherichia coli differ phylogenetically and by virulence profiles. Classic theory teaches simple linear descent in this species, where non-pathogens acquire virulence traits and emerge as pathogens. However, diarrheagenic Shiga toxin-producing E. coli (STEC) O2:H6 not only possess and express virulence factors associated with diarrheagenic and uropathogenic E. coli but also cause diarrhea and urinary tract infections. These organisms are phylogenetically positioned between members of an intestinal pathogenic group (STEC) and extraintestinal pathogenic E. coli. STEC O2:H6 is, therefore, a ‘heteropathogen,’ and the first such hybrid virulent E. coli identified. The phylogeny of these E. coli and the repertoire of virulence traits they possess compel consideration of an alternate view of pathogen emergence, whereby one pathogroup of E. coli undergoes phased metamorphosis into another. By understanding the evolutionary mechanisms of bacterial pathogens, rational strategies for counteracting their detrimental effects on humans can be developed.Subject Categories Microbiology, Virology & Host Pathogen Interaction

Highlights

Escherichia coli are usually harmless inhabitants of the human gut
Multilocus sequence typing (MLST) (Wirth et al, 2006) demonstrates that 13 Shiga toxin-producing E. coli (STEC) O2:H6 strains isolated between 2000 and 2009 from epidemiologically unrelated patients with non-bloody diarrhea, whose illnesses resolved without progression to hemolytic uremic syndrome (HUS) and whose stools contained no other intestinal pathogens belong to sequence type (ST) 141
This ST is only distantly related to the STs of the non-H6 STEC O2, and is not found among STEC causing HUS (‘the HUSEC collection’) (Mellmann et al, 2008), intestinal pathogenic E. coli strains of other pathogroups (EPEC, ETEC, EIEC, EAEC, AIEC), prototypic Extraintestinal pathogenic E. coli (ExPEC) (UPEC and MNEC) strains, and in a non-pathogenic E. coli K-12

Summary

Introduction

Escherichia coli are usually harmless inhabitants of the human gut. some members of this species have acquired specific virulence attributes that allow them to cause intestinal as well as extraintestinal diseases in humans (Kaper et al, 2004). E. coli O157:H7 is the most common human pathogenic STEC (Karch et al, 2005), but a variety of non-O157:H7 STEC serotypes have been isolated from patients (Karch et al, 2005; Mellmann et al, 2008; Bielaszewska et al, 2013). These pathogens have acquired a rather stereotyped suite of virulence loci (‘parallel evolution’) (Reid et al, 2000; Ogura et al, 2009). Extraintestinal pathogenic E. coli (ExPEC) are classified as uropathogenic (UPEC), sepsisassociated, and meningitis-associated (MNEC) (Kaper et al, 2004)

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