How Eggs Can Harbor Salmonella, Even When They Look Perfectly Clean

Key Points to Remember About How Eggs Get Salmonella

• Eggs can get Salmonella from feces or contaminated litter that travels to a chicken’s reproductive tract. Bacteria can colonize where the egg white and shell form, thereby contaminating the egg.
• Salmonella represents a persistent risk to poultry farmers despite antibiotics and modern controls. Simply touching a contaminated surface can turn eggshell into a disease vector.
• Cooking exposes bacteria to heat, which can kill Salmonella. The FDA recommends heating eggs to an internal temperature of 165 degrees Fahrenheit (about 74 degrees Celsius).

At first glance, a clean, intact egg seems rather harmless, but a smooth shell can hide prickly enemies.

In August 2025, the Centers for Disease Control and Prevention (CDC) issued a brown egg recall in several states after nearly 100 people became ill, 18 of whom were hospitalized with high fevers, severe diarrhea, and a host of other illnesses.

The culprit: a particularly persistent food-borne bacteria known as Salmonella enteritidis. The microbe grows in animal intestines and raw meat, opportunistically scavenging any nutrients it encounters and multiplying rapidly.

Patients who are unlucky enough to experience its stomach turning symptoms are not uncommon either. In a 2010 article Clinical infectious diseasesresearchers estimated that on a global scale Salmonella causes approximately 93 million cases of infectious diarrhea and more than 100,000 deaths worldwide each year.

Despite the bacteria’s impressive infectious history, it is difficult to imagine that the microbe will end up inside a shell egg. But as is often the case in nature, life finds its way.

How to get eggs Salmonella?

According to Dr. Alexandra Grote, assistant professor of infectious diseases at Northwestern University Feinberg School of Medicine, “Salmonella Feces or contaminated litter can travel to the chicken’s reproductive tract,” says Grote. “From there, bacteria can colonize the oviduct, where the egg white and shell form, leading to contamination even before the shell hardens.”

The microbe’s impressive suite of adaptations allows it to survive in a variety of harsh environments.

“Salmonella is a generalist,” says Grote. “It can use nutrients that other microbes cannot, resist bile and acidic conditions, and compete with the resident microbiota.”

Salmonella is well known for its acid tolerance response (ATR), allowing it to regulate its internal pH and survive a trip to the stomach. A 2014 study from Current opinion in microbiology discovered that cells could remodel the structure of their outer membrane to better resist the salt and acidity of an inflamed gut.

Grote notes that even the shell of an egg is not safe, because bacteria can produce stress response proteins and enter a quasi-dormant state to survive dry conditions. Under the right circumstances, they can migrate inward through tiny pores or cracks on the surface of the egg.

Salmonella can also cleverly manipulate the host’s immune system, exploiting the inflammatory response it provokes to suppress its competitors.

“Salmonella doesn’t always want to multiply quickly,” adds Grote. “It may slow its growth or enter a dormant state. These “persistent” bacteria can survive antibiotics and immune attacks, only to reappear later.

Learn more: What are the different types of food poisoning and how can you avoid them?

What is the frequency Salmonella in eggs?

With all these capabilities at his disposal, Salmonella represents a persistent risk to poultry farmers despite antibiotics and modern controls. A study carried out in 2000 in the International Journal of Food Microbiology It is estimated that in the United States, 1 in 20,000 eggs may be “internally contaminated” with the bacteria.

Simply touching a contaminated surface can turn eggshell into a disease vector. In its official egg safety guidelines, the U.S. Food and Drug Administration (FDA) emphasizes the importance of purchasing refrigerated egg cartons and storing them below 40 degrees Fahrenheit (4 degrees Celsius) at home.

Can cooking eggs kill Salmonella?

The cold of a refrigerator slows bacterial growth, but it’s the fire of the stove that finishes the job. Fortunately for all humans, Salmonella I just can’t resist the heat.

A 2016 article published in the Journal of Food Science found that prolonged immersion in water around 130 degrees Fahrenheit resulted in a 99.99 percent reduction in the number of people alive. Salmonella cells.

To fully mitigate the threat, the FDA recommends heating eggs to an internal temperature of 165 degrees Fahrenheit (about 74 degrees Celsius).

“Cooking exposes bacteria to heat, which disrupts them on a molecular level,” Grote explains. “The proteins in the bacterial cell unfold and lose their function. The membrane itself leaks. Once these systems collapse, the bacteria can no longer survive.”

Some highly specialized microbes, like the inhabitants of Yellowstone’s hot springs, are adapted to thrive in the scalding waters, but infectious diseases like Salmonella will die.

As long as the eggs are cooked thoroughly, this hidden threat won’t pose a risk, but caution is never a bad idea. If you’re unsure whether your egg sandwich will cause digestive upset, it might be best to err on the side of caution before you can become infected.

This article does not offer medical advice and should be used for informational purposes only.

Learn more: With bird flu spreading, cooking eggs carefully may be beneficial

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