Preventing Eggs from Becoming Contaminated with Salmonella
By Dr. Ilane Hernández Morales, Veterinary Medicine and Zootechnology Unit, Universidad Nacional Autonóma de México, 2009 Pedro N. Acha Award for Excellence in Veterinary Public Health Winner

salmonella-egg-whisk-for-weThe salmonella outbreak in the U.S. has sickened more than 1,300 people and prompted massive egg recalls which have cost producers millions of dollars. To avoid future outbreaks, it is important to learn exactly how salmonella travels via a hen’s system to a human’s—and how it can be avoided.

Salmonella is an organism that causes gastro-enteric infections in mammals and reptiles. In humans, it is one of the major organisms responsible for foodborne diseases. 

Since the 1980s, the reported cases of salmonelosis in humans have increased. S. typhimurium and S. enteritidis are the most common types of salmonella responsible for infections. They infect poultry orally and then colonize internal organs such as the liver, kidney, spleen, intestine, and reproductive tract. After recovering from a salmonella infection, animals remain as carriers and spread the microorganism via their feces and/or eggs. 

 

How Salmonella Spreads

Eggs become contaminated in one of two ways. In the first, the egg comes into contact with contaminated feces. Salmonella then enters the egg via a crack in the shell. In the second method of transmission, known as trans-ovarian infection, salmonella replicates in the ovary and oviducts of the hen. The newly produced egg will carry the microorganisms. 

S. enteritidis is of major concern because it can survive within the egg for many days after the hen has produced it. This is not the case for S. typhimurium and is why S. enteritidis is now the most common bacteria found in human samples. The microorganism enters the body when people eat raw or undercooked eggs, or even from food products made with non-pasteurized eggs such as mayonnaise. 

 

How to Protect Yourself against Salmonella Transmitted by Eggs 

The recent salmonella outbreak in the U.S. demonstrates how consumers must be careful when consuming egg products, especially those prepared outside their home. 

By taking simple precautions, consumers can avoid salmonella infection by:

•    Avoiding consumption of raw eggs
•    Cooking eggs until the yolk is solid
•    Cooking eggs at 140ºF or hotter for at least five minutes
•    Washing kitchen materials used to prepare food with raw eggs 
•    Never consuming eggs that have not been properly refrigerated
•    Never consuming eggs with a broken shell 
•    Ensuring food is made with pasteurized eggs, especially mayonnaise, salad dressings, and cakes
 
 
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