How Escherichia coli O157:H7 Colonizes the Gut

Food Poisoning is becoming very frequent

Food poisoning caused by the bacteria enterohemorrhagic Escherichia coli (EHEC) O157:H7 results in severe abdominal cramps and bloody diarrhea. In the very young and old it can also cause hemolytic uremic syndrome (HUS) -- a disease characterized by anemia and kidney failure.

A new study by Jorge Girón and colleagues from the University of Arizona, Tucson, has provided new insight into the mechanisms by which EHEC colonize the intestines, which is essential if strategies to prevent infection by this bacteria are to be developed.

The authors determined that EHEC O157:H7 make a number of proteins that come together to form a structure known as an adhesive type IV pilus, which they termed the hemorrhagic coli pilus (HCP).

HCP were shown to enable EHEC O157:H7 to adhere to human intestinal epithelial cells in vitro. Furthermore, individuals with HUS, but not individuals who were healthy, were found to mount an immune response to the HCP component Hcp4, indicating that HCPs are produced by the bacteria during infection with EHEC O157:H7.

An escN mutant, which is unable to translocate Tir, adhered less than the hcpA mutant, suggesting that adherence mediated by intimin-Tir interactions is a prelude to HCP-mediated adherence. An hcpA and stx1, 2 triple mutant and an hcpA mutant had similar levels of adherence to bovine and human epithelial cells while a stx1,2 double mutant had only a minor defect in adherence, indicating that HCP-mediated adherence and cytotoxicity are independent events.

Source: Journal of Clinical Investigation, Oct 2007

Apoorte: Guillermo Figueroa