Review of the Food-borne Zoonoses Research ... - ARCHIVE: Defra

Project code: OZ 0704
Project title: Quantification of E. coli O157:H7 virulence factors in
vivo using real-time RT-PCR
Start date (dd/mm/yy): 01/06/1999
End date (dd/mm/yy): 30/09/2002
£200,764
Total cost:
Affiliation: Dept. Vet. Pathology, University of Glasgow
Sub-contractor(s): None
Abstract of research
The asymtomatic carrier bovine is a major reservoir of the food borne zoonotic E.coli
O157:H7. Previous studies have shown that an individual animal may shed organisms
intermittently throughout life and that infection/colonisation can be cleared but that the
same animal can also become reinfected. The main site of carriage in the adult bovine is
the colon although organisms have been described colonising other regions of the
alimentary tract in the adult carrier animal. E.coli O157:H7 has been reported to cause
disease in young calves and we have recently identified O157 organisms attached to
intestinal epithelium in an adult cow with profuse bloody diarrhoea.
Various virulence determinants - VT1, VT2, intimin, fimbrae - have been identified by
culturing E.coli O157 in vitro and in studies using mutated organisms. However, whilst
the role of some of these determinants in pathogenicity has been established, the precise
molecular events associated with colonisation, persistence of infection/carriage and
clearance of carriage have not been determined. In this project we will apply the new
and exciting technology of real-time, convential PCR and RT-PCR to quantitate the
number of organisms and the expression of mRNAs for various virulence factor produced
by E.coli O157:H7 organisms in vivo. This will be combined with in situ RT-PCR
techniques to obtain a detailed understanding of microbial gene expression during
colonisation/ attachment/carriage in the bovine alimentary tract.
Thus we will use modern molecular techniques to obtain a clearer understanding of the
distribution of infection and pathogenesis (expression of virulence determinants in vivo)
of E.coli O157:H7 in cattle. These data would underpin future studies investigating in
detail host responses in the carrier animal, relating these to microbial virulence factors
and host-pathogen interactions. The overall aim of this approach is to devise strategies
leading to reduction/elimination of the E.coli O157:H7 carrier state in cattle.
These studies therefore address MAFF policy relating to MAFF Strategic Research
Requirements to obtain a clearer understanding of the distrubution of infection,
pathology, colonisation, host specificity and virulence of the E.coli O157:H7 bacterium in
animals. Such knowledge is essential to the development of preventative and control
measures for O157 infection of animals, thereby reducing food contamination and the
incidence of O157 food poisoning in man.
Development of these techniques for E.coli O157:H7 could also form the basis of
investigating host-pathogen interactions of other food borne zoonoses at the molecular
level.
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