Pathogenic Organisms. The following is a summary of micro organisms that could be carried inside and on the outside of shell eggs and that is dangerous to humans.
Egg infection spoilage and pathogenicity in whole eggs is usually a result of infection by bacteria typically associated with the production environment and the health status of the layers.
Three routes of infection are typically identified. These are transovarian, where the yolk of the egg is infected while it is attached to the ovary; oviductal, where the vitelline membrane or the albumin is contaminated as they pass along the oviduct and trans-shell contamination, where the microorganisms enter the egg through the highly porous shell structures. The first two routes occur inside the chickens while the egg is being formed, while the third route occurs outside the chicken as a result of dirty environments. The primary pathogenic organism of concern to eggs is the Salmonella type. Salmonella spp. generally found in the environment usually contaminates the eggs via the shells, while a specific strain namely Salmonella enteritidis is associated with the two internal (transovarian and trans-oviductal) routes. The typical spoilage organisms associated with eggs causing egg shelf-life deterioration are
usually gram-negative bacteria and they are also transferred via the eggshell.