How does salmonella get into eggs?
Since a few hundred million eggs have been recalled, I'm wondering how salmonella gets into eggs in the first place. Is it getting on the shells from the environment (or the hen)? Is it inside the egg?
This is mostly a curiosity/science question, so please don't take it as fear mongering, FUD, or any such non-sense. I realize that many eggs are perfectly safe.
Best Answer
There are two basic mechanisms:
- the salmonella is on the shell and when the egg gets broken the interior gets contaminated; or
- the chicken's reproductive system is contaminated and lays an egg with contaminated interior.
To reduce the very common (a few percent) shell contamination, eggs sold commercially have their shells treated (typically washed). After washing only about 50 in every million eggs will still have some shell contamination. The shell contamination may have been there when the chicken laid the egg, from fecal matter, or as a result of plant processing.
In some rare cases the surface salmonella can make it to the inside without breaking the egg: if it was there while the cuticle dried, if the egg is stored at room temperature, or if the environment is moist.
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Quick Answer about "How does salmonella get into eggs?"
How do eggs get Salmonella on them? Salmonella can get on the shells of eggs when birds lay eggs or when the eggs touch bird droppings (poop) after being laid. This is not a problem for commercial eggs (for example, eggs you buy at the grocery store) because companies wash eggs before they reach stores.How common is Salmonella in eggs?
The Centers for Disease Control estimates that 1 in every 20,000 eggs are contaminated with Salmonella. Persons infected with Salmonella may experience diarrhea, fever, abdominal cramps, headache, nausea and vomiting.How do I know if my eggs have Salmonella?
You can't tell if an egg has salmonella just by looking at it. The bacteria can be present inside an egg as well as on the shell. Cooking food thoroughly can kill salmonella. Be aware that runny, poached, or soft eggs aren't fully cooked \u2014 even if they are delicious.Does Salmonella come from egg white or yolk?
Cooking reduces the number of bacteria present in an egg; however, an egg with a runny yolk still poses a greater risk than a completely cooked egg. Undercooked egg whites and yolks have been associated with outbreaks of Salmonella infections.Does Salmonella come from the outside of an egg?
Salmonella can lurk on the outside of eggs when they are not properly washed. But stringent procedures for cleaning and inspecting eggs implemented in the 1970s have made salmonellosis caused by external fecal contamination of egg shells extremely rare, the CDC says.More answers regarding how does salmonella get into eggs?
Answer 2
From LiveScience:
The bacteria, Salmonella enteritidis can invade an egg in several ways. One way is by the contamination of egg shells with fecal matter. The bacteria are present in the intestines and feces of infected humans and animals, including chickens, and can be passed to the eggs when chickens sit on them... Salmonella also silently infects the ovaries of healthy-looking hens, contaminating the eggs inside the chicken before the shells are even formed...
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