Campylobacter jejuni and Campylobacter coli: Dose Response Models
Campylobacter are microaerophilic gram-negative curved or spiral rods with a polar flagellum. C. jejuni and C. coli are common causes of gastroenteritis . It can cause acute self-limiting diarrhea in healthy humans with an incubation period of 2-3d, and appears very common worldwide. It is mainly a zoonosis, being primarily associated with birds (especially poultry). They do not grow in water and (like Escherichia coli) are an indicator of post-treatment contamination in water distribution systems.
According to feeding studies with chickens, strains of C. jejuni that have been passaged many times in the laboratory tend to have a lower ID50 than strains that are isolated from infected hosts and then used to infect new hosts, with minimal passage . Minimally passaged strains also had more variation in ID50 . Given safety concerns, strains used for human studies may be passaged and studied more, possibly underestimating infectiousness in actual human exposure scenarios .
Campylobacter epidemiology varies greatly between the developed and developing world, probably due to development of immunity early in life. Illness is rare after about 5 years of age (or earlier) in developing countries, but occurs among adults in industrialized countries, probably because they avoided exposure (and therefore immunity) in childhood . However, immunity appears to protect against disease rather than infection, and asymptomatic shedding is common . In a comparison of Mexican children <4 years of age and Swedish patients (ages not given), Swedish patients tended to carry only 1 Campylobacter serotype, while mixed serotypes were common among Mexican children (42%)
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