Contamination of eggs of laying hens with S. Enteritidis

The contamination of the eggs of laying hens can happen by horizontal and vertical ways. The horizontal way of the contamination is caused by the environmental occurrence of bacteria including the airborne mechanism, and the bacterial penetration through the eggshell is possible if the temperature conditions are warm enough. The vertical contamination occurs by ovarian transmission. The anatomy and physiology of the eggshell demonstrates the property as a barrier for bacterial penetration. After penetration through the eggshell the bacterium will be confronted with the antimicrobial peptides, the high pH and high osmolarity of the albumen. However, S. Enteritidis is able to adapt the phenotype. The migration of the bacterium into the nutritionally rich yolk is constrained by the lysozyme loaded vitelline membrane, and would need warm enough storage conditions within days and weeks. The high concentration on of antibodies of the yolk does not inhibit the Salmonella multiplication. The transovarian contamination of the developing eggs with S. Enteritidis will result in the occurrence of this bacterium in the laid eggs relatively seldom only, because of the bactericidal efficacy of the antimicrobial peptides. Generally, if Salmonella are present in the albumen it is the result of the penetration, and the occurrence in the yolk corresponds with an ovarian source. Due to the mechanisms of the egg contamination, Salmonella are very rare in eggs compared to their occurrence in the laying hens. Salmonella are more present in the albumen as in the yolk.