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Journal of Clinical Microbiology, October 2007, p. 3295-3301, Vol. 45, No. 10
0095-1137/07/$08.00+0     doi:10.1128/JCM.00471-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Comparative Analyses of Phenotypic and Genotypic Methods for Detection of Enterotoxigenic Escherichia coli Toxins and Colonization Factors{triangledown}

Å. Sjöling,1* G. Wiklund,1 S. J. Savarino,2 D. I. Cohen,3 and A.-M. Svennerholm1

WHO Collaborating Centre for Research on Enterotoxigenic Escherichia coli (ETEC), and Department of Microbiology and Immunology, Institute of Biomedicine, Göteborg University, Box 435, 40530 Göteborg, Sweden,1 Enteric Diseases Department, Naval Medical Research Center, 503 Robert Grant Avenue, Silver Spring, Maryland 20190,2 Department of Epidemiology and Preventive Medicine, Sackler Faculty of Medicin, Tel Aviv University Ramat Aviv, Tel Aviv 69978, Israel3

Received 2 March 2007/ Returned for modification 10 May 2007/ Accepted 30 July 2007

Enterotoxigenic Escherichia coli (ETEC) is one of the main causes of childhood diarrhea in developing countries and in travelers. However, this pathogen has often not been reported in surveys of diarrheal pathogens, due to lack of simple standardized methods to detect ETEC in many laboratories. ETEC expresses one or both of two different enterotoxin subtypes: heat-stable toxins, a heat-labile toxin (LT), and more than 22 different colonization factors (CFs) that mediate adherence to the intestinal cell wall. Here we compare established phenotypic and genotypic detection methods and newly developed PCR detection methods with respect to sensitivity, specificity, positive predictive value, and ease of performance. The methods include GM1-enzyme-linked immunosorbent assay and dot blot techniques using specific monoclonal antibodies (MAbs) for phenotypic detection of the toxins and CFs, respectively, as well as different PCR and DNA/DNA hybridization 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 analyzed 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 harbor silent CF genes.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, Institute of Biomedicine, Box 435, 405 30 Göteborg, Sweden. Phone: 46-31-7866232. Fax: 46-31-7866205. E-mail: asa.sjoling{at}microbio.gu.se

{triangledown} Published ahead of print on 8 August 2007.

Journal of Clinical Microbiology, October 2007, p. 3295-3301, Vol. 45, No. 10
0095-1137/07/$08.00+0     doi:10.1128/JCM.00471-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



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