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Journal of Clinical Microbiology, July 2009, p. 2061-2066, Vol. 47, No. 7
0095-1137/09/$08.00+0     doi:10.1128/JCM.00201-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Shiga Toxin, Cytolethal Distending Toxin, and Hemolysin Repertoires in Clinical Escherichia coli O91 Isolates{triangledown}

Martina Bielaszewska,1* Franziska Stoewe,1 Angelika Fruth,2 Wenlan Zhang,1 Rita Prager,2 Jens Brockmeyer,1 Alexander Mellmann,1 Helge Karch,1 and Alexander W. Friedrich1

Institute of Hygiene and the National Consulting Laboratory on Hemolytic Uremic Syndrome, University of Münster, Robert Koch Str. 41, 48149 Münster, Germany,1 National Reference Center for Salmonella and Other Bacterial Enteric Pathogens, Robert Koch Institute, Branch Wernigerode, Burgstr. 37, 38855 Wernigerode, Germany2

Received 30 January 2009/ Returned for modification 26 March 2009/ Accepted 20 April 2009

Shiga toxin (Stx)-producing Escherichia coli (STEC) strains of serogroup O91 are the most common human pathogenic eae-negative STEC strains. To facilitate diagnosis and subtyping of these pathogens, we genotypically and phenotypically characterized 100 clinical STEC O91 isolates. Motile strains expressed flagellar antigens H8 (1 strain), H10 (2 strains), H14 (52 strains), and H21 (20 strains) or were H nontypeable (Hnt) (10 strains); 15 strains were nonmotile. All nonmotile and Hnt strains possessed the fliC gene encoding the flagellin subunit of the H14 antigen (fliCH14). Most STEC O91 strains possessed enterohemorrhagic E. coli hlyA and expressed an enterohemolytic phenotype. Among seven stx alleles identified, stx2dact, encoding mucus- and elastase-activatable Stx2d, was present solely in STEC O91:H21, whereas most strains of the other serotypes possessed stx1. Moreover, only STEC O91:H21 possessed the cdt-V cluster, encoding cytolethal distending toxin V; the toxin was regularly expressed and was lethal to human microvascular endothelial cells. Infection with STEC O91:H21 was associated with hemolytic-uremic syndrome (P = 0.0015), whereas strains of the other serotypes originated mostly in patients with nonbloody diarrhea. We conclude that STEC O91 clinical isolates belong to at least four lineages that differ by H antigens/fliC types, stx genotypes, and non-stx putative virulence factors, with accumulation of virulence determinants in the O91:H21 lineage. Isolation of STEC O91 from patients' stools on enterohemolysin agar and the rapid initial subtyping of these isolates using fliC genotyping facilitate the identification of these emerging pathogens in clinical and epidemiological studies and enable prediction of the risk of a severe clinical outcome.

* Corresponding author. Mailing address: Institut für Hygiene, Universität Münster, Robert Koch Str. 41, 48149 Münster, Germany. Phone: 49-251-980 2849. Fax: 49-251-980 2868. E-mail: mbiela{at}uni-muenster.de

{triangledown} Published ahead of print on 29 April 2009.

Journal of Clinical Microbiology, July 2009, p. 2061-2066, Vol. 47, No. 7
0095-1137/09/$08.00+0     doi:10.1128/JCM.00201-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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