Persistence of Salmonella enteritidis from one day of age until maturity in experimentally infected layer chickens.

In each of two replicate trials, 1-d-old chicks were inoculated orally with a phage type 13 Salmonella enteritidis isolate (resistant to nalidixic acid). Although S. enteritidis was found in the livers, spleens, and ceca of all sampled chicks at 1 wk postinoculation, colonization generally persisted beyond 4 wk postinoculation only in the ceca. Nearly half of the remaining hens were still shedding S. enteritidis in their feces at 24 wk of age, but only 1 of 62 hens laid eggs that were internally contaminated with S. enteritidis during the initial 4 to 6 wk of egg production. Chickens exposed to S. enteritidis shortly after hatching can apparently remain infected until maturity, at which time they might produce contaminated eggs or spread the infection to other susceptible, previously unexposed hens.