Origins of the E. coli Strain Causing an Outbreak of Hemolytic-Uremic Syndrome in Germany


2011-08-26 | Admin MKKI

In early May 2011, an outbreak of diarrhea with associated hemolytic–uremic syndrome began in northern Germany; cases have subsequently been reported in 15 other countries. As of July 22, a total of 3167 cases of non–hemolytic–uremic syndrome Shiga-toxin–producing Escherichia coli (16 deaths) and 908 cases of hemolytic–uremic syndrome (34 deaths) have been reported, according to the German Protection against Infection Act.

Several groups reported that the outbreak was caused by a Shiga-toxin–producing E. coli strain belonging to serotype O104:H4, with virulence features that are common to the enteroaggregative E. coli pathotype.1-3 This unusual E. coli serotype has previously been associated with sporadic cases of human disease4,5 but not with large-scale outbreaks.

E. coli are ordinarily commensal organisms, but six pathotypes of diarrheagenic E. coli are recognized, each with distinct phenotypic and genetic traits. Diarrhea associated with the hemolytic–uremic syndrome and neurologic complications is generally caused by E. coli that produce Shiga toxins. The majority of such strains, often referred to as enterohemorrhagic E. coli, contain the enterocyte effacement pathogenicity island, which facilitates colonization of the large intestine.

Unexpectedly, polymerase-chain-reaction assays revealed that the German outbreak strain lacked this pathogenicity island, and the rapidly released results of genomic sequencing and cell adherence assays confirmed the initial observations that the German O104:H4 outbreak strain was an enteroaggregative E. coli strain rather than a typical enterohemorrhagic E. coli strain. The outbreak strain was similar to enteroaggregative E. coli O104:H4 strain 55989, isolated from a patient in the Central African Republic who had human immunodeficiency virus infection (HIV) with persistent diarrhea, which did not produce Shiga toxin.

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