Supershedders on the Farm

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Science  07 Mar 2003:
Vol. 299, Issue 5612, pp. 1489
DOI: 10.1126/science.299.5612.1489a

Escherichia coli O157:H7 produce Shiga toxins, which cause bloody diarrhea and potentially fatal systemic infections in humans. Cattle are thought to be the main source of these dangerous organisms, but they themselves show few symptoms of infection. Naylor et al. surveyed four strains of O157:H7 in experimentally infected calves. Most bacteria were found in feces, and after necropsy it was observed that the recto-anal tissues contained adherent colonies of O157:H7. These tissues also have a high density of lymphoid follicles, which may be governing this tropism, possibly via the bacterial adhesion protein intimin. By contrast, other E. coli serotypes were distributed evenly throughout the large intestine. This is a novel tissue tropism for a pathogen, which appears to be an adaptation to maximizing transmission among natural hosts and one that could also allow ready diagnosis and treatment of the carrier status of a herd. — CA

Inf. Immun. 71, 1505 (2003).

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