Human infection is usually acquired by the consumption of contaminated food (especially poultry) or water1. Motile campylobacters colonize the intestines of a wide range of animals, but in immunologically naive humans infection frequently results in an inflammatory enterocolitis. The number of cases of Campylobacter infection reported in England and Wales in 1998 increased by 17% from the previous year, with the number of reported cases now more than double that due to Salmonella3. Despite its importance, effective control of Campylobacter in the food chain and the design of disease prevention strategies are hindered by a poor understanding of the genetics, physiology and virulence of this organism.