Intestinal carriage and excretion of Campylobacter jejuni in chickens exposed at different ages.

Campylobacter jejuni is usually recovered from chickens in commercial broiler farms after 2 to 3 weeks of age. This study was conducted to clarify whether fecal excretion is associated with the age of exposure to this bacterium. Day-of-hatch broiler chickens were separated from a flock in a local commercial farm, kept in isolation rooms, and esophageally inoculated with C. jejuni (5.5 × 10(7) to 5.4 × 10(8) CFU) at 0, 7, 14, 21, 28, and 35 days of age. The remaining chicks were placed on the farm. Fecal samples obtained from the birds with the experimental infection and those reared on the farm were monitored for C. jejuni. Cecal contents obtained on necropsy were also cultured. In chickens inoculated with C. jejuni at 0 to 14 days of age, fecal excretion of C. jejuni was not observed until 42 days of age, although the organism was recovered from the cecal contents of these birds. When chickens were inoculated at 21 to 35 days of age, C. jejuni was isolated from fecal samples 2 or 3 days after inoculation, and the birds continually shed the organism until they reached 49 days of age, with the maximal numbers of the organism ranging from 1.7 × 10(8) to 1.0 × 10(10) CFU/g. In the commercial broiler farm, C. jejuni was first isolated from fecal samples obtained from two of five chickens at 28 days of age, and the organism was isolated from all five birds tested at 43 days of age. Restriction fragment length polymorphism analysis of the fla gene of C. jejuni isolates revealed that birds on the farm were colonized with C. jejuni after placement of the chickens on the farm. These observations indicate that chickens younger than 2 to 3 weeks old may carry C. jejuni in the ceca if they were exposed to this organism. Our results also suggest that fecal excretion of C. jejuni in commercial broiler chickens older than 3 to 4 weeks of age may be mainly caused by exposure of chickens at this age to this organism.