Guide to the various phylogenetic classification schemes for Escherichia coli and the correspondence among schemes

Abstract

Numerous tools allowing the rapid and universal identification of the clones/clonal complexes/ phylogroups of Escherichia coli have been developed, as it is a commensal of the vertebrate gut, a major pathogen in veterinary and human medicine, and a bacterial indicator of faecal contamination. The ability to identify clones/clonal complexes/phylogroups is crucial, as a strain’s ecological niche, lifestyle and propensity to cause disease vary with its phylogenetic origins. There are currently three multi-locus sequence typing (MLST) schemes for E. coli, as well as several PCR-based assays for determining a strain’s phylogroup or clonal complex. In this work, we present data that will enable investigators to determine the correspondence between the PCRbased assays and the three MLST schemes, and provide the means for assigning a sequence type (ST) to a phylogroup when no other data on the strain phylogroup membership are available. Such information will help the scientific community to accurately identify the E. coli clones reported in various publications. Although whole-genome sequencing will replace classical MLST and most alternative PCR-based methods, the ST nomenclature of the MLST scheme hosted at the University of Warwick will largely persist.