Why can Salmonella enteritidis sometimes be present inside an egg?

While most eggs are free of contamination when laid, Salmonella enteritidis can occasionally be present inside an egg because it is transferred through the hen's ovary before the shell is formed. This ovarian transmission occurs in fewer than 1 percent of all eggs produced.1

It is important to note that while washing and sanitizing eggs effectively removes most bacteria deposited on the shell surface, this process cannot eliminate bacteria that are already inside the egg. To ensure food safety and protect against potential food poisoning, it is essential to cook eggs thoroughly until both the whites and the yolk are firm, as this heat treatment effectively controls the bacteria.1