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Combined Virulence Identified in E. coli O104:H4

E. coli O104:H4 strain has high intestinal adherence with virulence of two pathogens

THURSDAY, June 23 (HealthDay News) -- The high virulence of Escherichia coli (E. coli) O104:H4 may be due to the strain having combined virulence of Shiga-toxin-producing and enteroaggregative E. coli, and augmented adherence to intestinal cells, according to a study published online June 23 in The Lancet Infectious Diseases.

Martina Bielaszewska, M.D., from the University of Münster in Germany, and colleagues investigated the virulence profiles and related phenotypes of E. coli strain O104:H4 outbreak isolates recovered from stool samples of 80 patients with hemolytic uremic syndrome, between May 23 and June 2, 2011. Using standard polymerase chain reaction (PCR), isolates were screened for virulence genes of Shiga-toxin-producing E. coli, and characteristic features of the outbreak strains were screened with a new multiplex PCR. Shiga-toxin production and epithelial cell adherence were measured, stx was sequenced with Sanger sequencing, and phylogeny and antimicrobial susceptibility were determined.

The investigators found that all isolates belonged to HUSEC041 clone. The combined virulence profiles of typical Shiga-toxin-producing E. coli and enteroaggregative E. coli were shared by all isolates. All isolates expressed phenotypes that define Shiga-toxin-producing and enteroaggregative E. coli, such as production of Shiga-toxin 2 and aggregative adherence to epithelial cells. They also demonstrated an extended-spectrum β-lactamase phenotype which is not found in HUSEC041.

"The genotypes, phenotypes, and phylogeny of the 80 outbreak isolates demonstrate that the E. coli O104:H4 outbreak strain is a clone that combines virulence potentials of two different pathogens: Shiga-toxin-producing E. coli and enteroaggregative E. coli," the authors write.

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