Ecology of Campylobacter colonization in poultry: Role of maternal antibodies in protection and sources of flock infection.

摘要

Campylobacter jejuni, a gram-negative organism, is a leading bacterial cause of human foodborne enterocolitis worldwide. Although poultry are considered the major reservoir for this human pathogen, the ecology of Campylobacter in chicken flocks is poorly understood, hampering the design of effective intervention strategies at the preharvest stage. In the first part of this project, the prevalence, antigenic specificity, and bactericidal activity of poultry Campylobacter maternal antibodies were investigated. High levels of specific antibodies were detected in egg yolks, sera of broiler breeders, and young broiler chicks, as maternally-derived antibodies. These antibodies were against multiple outer membrane components of Campylobacter, and active in antibody dependent complement-mediated killing of C. jejuni. These findings indicated the widespread presence of functional Campylobacter antibodies in the poultry production system, and prompted us to conduct the second part of the project to determine the effect of Campylobacter maternal antibodies on the colonization of young chickens by C. jejuni using challenge studies. Laboratory inoculation of commercial broilers of different ages showed that the onset of colonization occurred much sooner in birds challenged at the age of 21-days (which are naturally negative for Campylobacter antibody) than it did in the birds inoculated at 3-days of age (which are naturally positive for Campylobacter maternal antibody). Also, challenge experiments using laboratory-raised specific pathogen-free (SPF) chickens demonstrated that significant decreases in the percentage of colonized chickens were observed during the first week post inoculation in 3-day old SPF chicks with Campylobacter maternal antibody as compared with 3-day old chicks without Campylobacter-specific maternal antibody. These results indicated that Campylobacter maternal antibodies play a partial role in protecting young chickens against colonization by C. jejuni.; In the last part of this study, we investigated the ability of Campylobacter to penetrate eggshells, its survival within eggs, and its prevalence in eggs from various sources to determine if vertical (egg-borne) transmission of Campylobacter occurred. Using a temperature differential method, it was shown that Campylobacter was either unable to penetrate the eggshell or did not survive up to 48 h inside the incubating eggs. C. jejuni survived for up to 14 days in eggs stored at 18°C following injection into the egg yolk; however, viability of the bacterium was dramatically reduced when injected into the albumen or the air sac. (Abstract shortened by UMI.)