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

Project code: OZ0707
Project title: Identification of factors mediating intestinal
colonisation of cattle by enterohaemorrhagic
Escherichia coli O157:H7.
Start date (dd/mm/yy): 01/10/1999
End date (dd/mm/yy): 11/04/2007
£603,124
Total cost:
Affiliation: Institute for Animal Health, Compton.
Sub-contractor(s): None
Abstract of research
Enterohaemorrhagic Escherichia coli (EHEC) comprise a group of zoonotic diarrhoeal
pathogens of worldwide importance. Human infections are frequently caused by direct or
indirect contact with ruminant faeces and may be complicated by haemorrhagic colitis
and life-threatening renal and neurological sequelae. Strategies to reduce the prevalence
of EHEC in ruminants are predicted to lower the incidence of human infections; however
the molecular mechanisms influencing intestinal colonisation of food-producing hosts by
EHEC are ill-defined. Defra-funded research conducted under project OZ0707 aimed to
understand this process in greater detail and to exploit the knowledge to develop, test
and refine novel methods of disease control. The research involved the most
comprehensive survey for EHEC virulence factors performed to date and yielded
valuable insights that could not have been obtained in surrogate rodent or cell-based
assays. The project involved targeted and genome-wide mutagenesis of E. coli O157:H7
and analysis of wild-type and mutant strains in vitro and in bovine oral challenge, ligated
intestinal loop and ex vivo organ culture assays. The information led to the testing of
several subunit vaccines in cattle and has been disseminated via numerous high-impact
publications, review articles and invited lectures.
Review Summary
This research has contributed to the evidence base for VTEC O157 and to the
development of improved methods of control. The study provided baseline data on the
mechanisms of colonization in cattle with E. coli O157 and showed that it might be
difficult to develop functional vaccines. The work was carried out to a high scientific
standard and resulted in several publications in high-impact journals.
Major colonization factors of E. coli O157 were identified but vaccination studies with
purified antigen indicated, however, that colonization was not inhibited even in the
presence of high-titre antibodies against these adhesion factors. The results indicated
that the way forward may be to construct non-pathogenic probiotic strains that might
occupy the niche which is currently used by pathogenic E. coli O157.
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