ABSTRACT
Enterohemorrhagic Escherichia coli (EHEC) are the most common cause of postdiarrheal hemolytic-uremic syndrome (HUS).
The most important EHEC serotype implicated worldwide is O157:H7. However, several
so-called non-O157 EHEC serotypes have emerged. After a mean incubation period of
3 days, patients develop watery diarrhea accompanied by cramping abdominal pain. During
the next days, in most patients watery diarrhea changes to bloody diarrhea. One week
after the onset of diarrhea, in about 15% of infected patients under 10 years of age
EHEC infection results in a systemic complication, HUS. Shiga toxins (Stxs) are considered
the major virulence factors of EHEC involved in the pathogenesis of HUS. It is generally
believed that after intestinal infection with EHEC, Stxs cross the intestinal barrier
and bind to endothelial cells. At this point they presumably injure the host cell
by inhibition of protein synthesis, stimulation of prothrombotic messages, or induction
of apoptosis. The B subunit of Stx binds to the membrane receptor globotriaosylceramide
(Gb3). Gb3 facilitates the endocytosis and intracellular trafficking of the toxin.
The Stx A subunit hydrolyzes a specific adenine residue of the 60S ribosomal subunit
of mammalian cells. As a consequence, Stx shuts down the protein machinery of the
susceptible cell. The HUS is the net effect of a variety of interacting factors, including
background risk of acquisition, host factors (such as age), virulence characteristics
of the infecting EHEC strain, and exogenous factors. All known EHEC virulence determinants
are located on mobile genetic elements, and this has an important impact on the evolution
of these pathogens. The evolution of EHEC has a dynamic component that includes different
genetic mechanisms. The recent progress in understanding the pathogenesis and epidemiology
of EHEC infections forms a basis for the development of future strategies to prevent
EHEC infections in humans.
KEYWORD
Hemolytic-uremic syndrome - HUS -
Escherichia coli
- E. coli O157 - epidemiology - Shiga toxins - enterohemorrhagic E. coli
