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Applied and Environmental Microbiology, May 2007, p. 3380-3390, Vol. 73, No. 10
0099-2240/07/$08.00+0     doi:10.1128/AEM.02855-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Identification of Unconventional Intestinal Pathogenic Escherichia coli Isolates Expressing Intermediate Virulence Factor Profiles by Using a Novel Single-Step Multiplex PCR

Institut für Infektiologie, Zentrum für Molekularbiologie der Entzündung (ZMBE), Westfälische Wilhelms-Universität Münster,¹ Institut für Hygiene, Universitätsklinikum Münster, D-48149 Münster,² Robert-Koch Institut, Bereich Wernigerode, D-38855 Wernigerode, Germany³

Received 8 December 2006/ Accepted 7 March 2007

Intestinal pathogenic Escherichia coli represents a global health problem for mammals, including humans. At present, diarrheagenic E. coli bacteria are grouped into seven major pathotypes that differ in their virulence factor profiles, severity of clinical manifestations, and prognosis. In this study, we developed and evaluated a one-step multiplex PCR (MPCR) for the straightforward differential identification of intestinal pathotypes of E. coli. The specificity of this novel MPCR was validated by using a subset of reference strains and further confirmed by PCR-independent pheno- and genotypic characterization. Moreover, we tested 246 clinical E. coli isolates derived from diarrhea patients from several distinct geographic regions. Interestingly, besides strains belonging to the defined and well-described pathotypes, we identified five unconventional strains expressing intermediate virulence factor profiles. These strains have been further characterized and appear to represent intermediate strains carrying genes and expressing factors associated with enteropathogenic E. coli, Shiga toxin-producing E. coli, enterotoxigenic E. coli, and enteroaggregative E. coli alike. These strains represent further examples of the extraordinary plasticity of the E. coli genome. Moreover, this implies that the important identification of specific pathotypes has to be based on a broad matrix of indicator genes. In addition, the presence of intermediate strains needs to be accounted for.

Published ahead of print on 30 March 2007.