Campylobacter are the largest cause of human bacterial gastroenteritis and contaminated poultry meat is a major source of infection. This contamination of the poultry meat comes from Campylobacter which can persist asymptomatically in the avian GI-tract even in the face of strong adaptive responses.
Multiple surface epitopes of Campylobacter strains are subject to high frequency, reversible switches in gene expression referred to as phase-variation. The phase-variable epitopes include glycans and other modifications of the capsule, flagella and lipooligosaccharide and switches in surface expression of outer membrane proteins which are predicted to facilitate host adaptation of this bacterium in particularly evasion of adaptive immune responses. The aim of this work is to determine if there is a role for phase variation during persistence in chickens.
We have developed an assay to detect changes in the lengths of the 28 polyG/polyC phase variable genes of C. jejuni strain NCTC11168. The percentage expression states for each gene and combinatorial expression states (phasotypes) were determined during colonisation of broilers at 14, 28 and 52 days post infection. Variation was not observed for all PV regions but trends were detected in colonised birds where by heightened levels of variation could be observed over time in individual birds. Independence testing indicated that some genes switching showed dependence on other switches.
Patterns of expression for individual genes, different functional groups and phasotypes will be discussed in the context of on-going research into growth effects on phasotypes and experimental/theoretical studies of population bottlenecks and selection.
The results indicate that switching may be essential for some surface components while others are do not appear to be relevant for persistence.
The project is funded by the BBSRC, FSA and Defra, UK.