The effect of feed deprivation on tissue invasion by Salmonella enteritidis.

A tissue culture procedure was utilized to compare tissue cell invasion by Salmonella enteritidis from molted and full feed hens. Three identical trials were performed in which 80-wk-old active laying hens were divided into 2 groups of 6 birds each. The molted hen group was subjected to a 14-d feed withdrawal, and the full-fed hen group was administered a standard layer ration. After feed treatment, crop, ileum, cecum, and ovary (small and large yellow follicles removed) were collected, rinsed in PBS, and placed into 50 mL of RPMI medium. The ends of intestine and crop tissues were tied to allow attachment of Salmonella only to the lumen surface. The RPMI medium containing 10(7) to 10(8) cfu of novobiocin and nalidixic acid-resistant phage type 13 Salmonella enteritidis was injected into the lumen of the intestine and crop tissues. Additionally, ovaries were incubated in 50 mL of RPMI medium containing 10(6) to 10(7) cfu of the Salmonella enteritidis. Tissues were incubated with Salmonella at 37 degrees C for 2 h, after which tissues were placed in 50 mL of fresh RPMI medium containing 500 microg/mL of gentamicin and incubated for 5 h at 37 degrees C to remove any Salmonella that had not penetrated tissues. Tissues were rinsed, stomached in 10 mL of PBS, serially diluted, and plated onto brilliant green agar containing novobiocin and nalidixic acid for Salmonella enumeration. Salmonella invasion of ovaries was reduced in tissues from molted hens in trials 1 and 2 as compared with full-fed controls (> 1.2 log reduction) but not in trial 3. Salmonella invasion of ceca from molted hens was numerically increased in trials 1 and 2 and significantly increased in trial 3 as compared with controls (> 0.8 log increase). No significant differences in Salmonella invasion were detected for crops and ileum. These data suggest that molting may affect invasion of tissues by Salmonella enteritidis.