Salmonella typhimurium penetration through the eggshell of hatching eggs

This study was undertaken to demonstrate penetration of Salmonella typhimurium through the eggshell of newly laid broiler hatching eggs. Eggs were challenged either by lightly spraying the bacteria over the blunt end of the egg or by contact with contaminated dry nest litter. Exposure time for both groups was 10 minutes; afterward, all eggs were disinfected and incubated 19 days under normal conditions. Chorioallantoic membranes and yolk sacs were cultured in brain-heart infusion broth on day 19 to demonstrate penetration. Isolation of the bacteria from chorioallantoic membranes and yolk sacs, respectively, were as follows: sprayed group: 100% and 83%; contact group: 59% and 29%. These results showed that although water enhanced S. typhimurium penetration, its presence on the eggshell is not essential for penetration to occur.