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Comparative analyses of phenotypic and genotypic methods for detection of enterotoxigenic Escherichia coli (ETEC) toxins and colonization factors

Journal article
Authors Åsa Sjöling
Gudrun Wiklund
Stephen Savarino
D. I. Cohen
Ann-Mari Svennerholm
Published in J Clin Microbiol
Volume 45
Issue 10
Pages 3295-3301
ISSN 0095-1137
Publication year 2007
Published at Institute of Biomedicine, Department of Microbiology and Immunology
Pages 3295-3301
Language en
Subject categories Microbiology in the medical area


Enterotoxigenic Escherichia coli (ETEC) is one of the main causes of childhood-diarrhoea in developing countries and in travellers. However, this pathogen has often not been reported in surveys of diarrhoeal pathogens due to lack of simple standardized methods to detect ETEC in many laboratories. ETEC express one or both of two different enterotoxin subtypes; heat stable toxins (STh and STp), a heat labile toxin (LT) and more than 22 different colonisation factors (CFs) that mediate adherence to the intestinal cell wall. Here we compare established phenotypic and genotypic methods and newly developed PCR methods with respect to sensitivity, specificity, positive predictive value and ease of performance. The methods include GM1-ELISA and dot blot techniques using specific monoclonal antibodies (MAbs) for the phenotypic detection of the toxins and CFs, respectively as well as different PCR and DNA/DNA hybridisation techniques, including new PCR assays, for genotypic identification of the toxin and CF genes, respectively. We found very good general agreement in results derived from genotypic and phenotypic methods. In a few strains, LT and CFs were identified genetically but not phenotypically. Based on our analyses we recommend initial screening for ETEC in clinical samples by multiplex toxin gene PCR. Toxin positive strains may then be analysed by dot-blot tests for detection of the CFs expressed on the bacterial surface and by PCR for determination of additional CFs for which MAbs are currently lacking as well as for strains that harbour silent CF genes.

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