ARS | Publication request: Effect of passage through laying hens on organ invasiveness and phenotypic heterogeneity of Salmonella enteritidis

Submitted to: Poultry Science Association Meeting Abstract
Publication Type: Abstract
Publication Acceptance Date: March 15, 2008
Publication Date: July 24, 2008
Citation: Gast, R.K., Bouldin, J.G., Guraya, R., Holt, P.S. 2008. Effect of passage through laying hens on organ invasiveness and phenotypic heterogeneity of Salmonella enteritidis. Poultry Science. 87(1):54.

Technical Abstract: Horizontal transmission within and between flocks is an important aspect of the epidemiology of Salmonella enteritidis (SE) in poultry. Previously, a series of passages through infected laying hens increased the frequency at which an SE isolate was deposited inside eggs. The present study evaluated the effect of in vivo passage of an SE isolate on its ability to invade to internal tissues and its expression of a phenotypic property (biofilm production) associated with invasiveness and egg contamination. In each of 3 trials, a group of laying hens was infected orally with a PT13a strain of SE (prepared from a separate stock culture each time). After internal organ samples were removed for culturing at 7 days post-inoculation, an SE isolate from the upper oviduct of an extensively infected hen was used to infect a second group of hens in each trial. In trial 1, the frequency of SE isolation from organs declined from 40% to 12% between the 2 rounds of infection, but the frequency of biofilm production by SE colonies obtained from round 2 organ samples (98%) was higher than for the original inoculum culture (59%). In trial 2, no colonies from either the inoculum strain or round 2 organ isolates were biofilm-positive, and the frequency of SE isolation from organs increased from 27% to 42% between rounds 1 and 2. In trial 3, the frequency of SE isolation from organs was similar in the 2 rounds of infection (61% and 58%), but the frequency of biofilm production by round 2 organ isolates (58%) was lower than for the original inoculum strain (88%). Passage of SE through infected chickens did not always select for a higher ability to invade internal organs in the present study. Moreover, in vivo passage did not consistently select for either increased or decreased phenotypic diversity within the overall SE population. The characteristics of the original inoculum population, the selective pressure exerted in the tissues of infected chickens, and the exact proportions of relevant phenotypic subpopulations actually transferred to subsequently infected birds may combine to determine the outcome.