Submitted to: International Journal of Poultry Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/13/2009
Publication Date: 2/13/2009
Citation: Gast, R.K., Bouldin, J.G., Guraya, R., Holt, P.S. 2009. Effect of prior passage through laying hens on invasion of reproductive organs by Salmonella Enteritidis. International Journal of Poultry Science. (8):116-121. Interpretive Summary: Horizontal transmission of Salmonella enteritidis (SE) between hens is an important mechanism by which infections spreads throughout laying flocks. In a previous study, passing an SE strain through several groups of hens increased its ability to cause egg contamination. The present study determined how passage through hens affected the ability of an SE strain to invade to various internal tissue sites, including three different locations in the reproductive tract. In each of three trials, groups of hens were infected with an oral dose of an SE stock culture. Internal organs from these hens were removed 7 days later and cultured to recover SE. An SE isolate from this first passage group was then used to infect a second passage group of hens and internal organs were again removed for culturing after 7 days. The overall frequency of S. Enteritidis isolation from internal organs increased between passages in only one of the three trials, and no increases were observed between passages in the frequency of S. Enteritidis recovery from any of the three reproductive tissue sites. Therefore, passage of SE through infected chickens did not always select for a higher ability to invade internal organs.
Technical Abstract: The colonization of reproductive tissues in infected laying hens is a pivotal stage in the production of contaminated eggs that can transmit Salmonella Enteritidis infections to humans. In an earlier study, a series of passages through infected laying hens increased the frequency at which an S. Enteritidis isolate was deposited inside eggs. The present study evaluated the effect of in vivo passage of an S. Enteritidis isolate on its ability to invade to internal tissues, including three different regions of the reproductive tract. In each of three trials, a group of laying hens was infected orally with a PT13a strain of S. Enteritidis (prepared from a separate stock culture each time). After internal organ samples were removed from this first passage group for culturing at 7 days post-inoculation, an S. Enteritidis isolate from the upper oviduct of an extensively infected hen was used to infect another (second passage) group of hens in each trial. The overall frequency of S. Enteritidis isolation from internal organs increased between passages in only one of the three trials, and no increases were observed between passages in the frequency of S. Enteritidis recovery from any of the three reproductive tissue sites. Therefore, passage of S. Enteritidis through infected chickens did not always select for either higher overall invasiveness or for a higher ability to colonize reproductive organs in the present study.