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

Project code: OZ0607
Project title: An investigation of the distinguishing features of C.
jejuni strains that have host/disease associations.
Start date (dd/mm/yy): 01/07/01
End date (dd/mm/yy): 30/06/04
£508,987
Total cost:
Affiliation: Veterinary Laboratories Agency (Weybridge)
Sub-contractor(s):
Abstract of research
The attribution of poultry as the major source of human campylobacteriosis remains
debatable. In order to inform risk assessment models, this project aimed to investigate
the role of other livestock as potential sources and the possibility that all strains of
campylobacter were pathogenic for humans. A multi-pronged approach was therefore
adopted to investigate the relationships between C.jejuni pathogenicity and host. Initial
studies using higher disciminatory MLST-based approaches demonstrated that the
populations of C. jejuni from human cases and from colonised animals overlap
significantly, indicating all veterinary campylobacters are potentially pathogenic to man.
However, at least one host-associated cluster was evident in pigs. Additionally, genomic
stability and instability were important factors in the ecology of this bacterial species.
A second approach investigated the molecular pathogenesis of disease, in order to
identify virulent and non-virulent organisms. In vitro assays indicated that there were no
obvious associations between genotype and putative campylobacter virulence properties,
therefore, attempts were made to identify specific genetic markers of virulence. A
transposon mutant library was produced and invasion-deficient mutants selected, which
may provide future markers of invasiveness. Rapid molecular assays for screening CDT
activity were developed and for the first time the immunogenicity of CDT was
investigated using a novel neutralisation assay. Human anti-CDT antibodies were
detectable in infected humans but no antibodies were detected in colonised chickens
indicating a host-related specificity in response. Additionally significant progress was
made on the identification of a fimbrial surface structure.
Finally, a sentinel study was undertaken which demonstrated passage-associated
changes in the genome sequence strain, NCTC11168, resulting in differences in chick
colonisation, motility, morphology and invasiveness. Transcript analysis demonstrated
changes in expression of a number of genes involved with the adaptation to microaerobic
growth. This work is of huge significance to the research community by clarifying the
importance of strain origin in virulence and physiological studies.
Review summary
At the start of project OZ0607 it was beginning to be recognised that poultry is not the
only source for human campylobacter infection, and not all strains of campylobacter are
pathogenic to humans. In order to more accurately attribute disease source and identify
potential control measures, indicators of the relationships between strains, pathogenicity
and host were required.
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