Salmonella Enteritidis Infection
What is salmonella enteritidis infection?
Egg-associated salmonellosis is an important public health problem in the
United States and several European countries. A bacterium, Salmonella
enteritidis, can be inside perfectly normal-appearing eggs, and if the eggs are
eaten raw or undercooked, the bacterium can cause illness. During the 1980s,
illness related to contaminated eggs occurred most frequently in the
northeastern United States, but now illness caused by S. enteritidis is
increasing in other parts of the country as well. Consumers should be aware of
the disease and learn how to minimize the chances of becoming ill.
A person infected with the Salmonella enteritidis bacterium usually has
fever, abdominal cramps, and diarrhea beginning 12 to 72 hours after consuming a
contaminated food or beverage. The illness usually lasts 4 to 7 days, and most
persons recover without antibiotic treatment. However, the diarrhea can be
severe, and the person may be ill enough to require hospitalization.
The elderly, infants, and those with impaired immune systems may have a more
severe illness. In these patients, the infection may spread from the intestines
to the blood stream, and then to other body sites and can cause death unless the
person is treated promptly with antibiotics.
How do eggs become contaminated?
Unlike eggborne salmonellosis of past decades, the current epidemic is due to
intact and disinfected grade A eggs. Salmonella enteritidis silently infects the
ovaries of healthy appearing hens and contaminates the eggs before the shells
Most types of Salmonella live in the intestinal tracts of animals and birds
and are transmitted to humans by contaminated foods of animal origin. Stringent
procedures for cleaning and inspecting eggs were implemented in the 1970s and
have made salmonellosis caused by external fecal contamination of egg shells
extremely rare. However, unlike eggborne salmonellosis of past decades, the
current epidemic is due to intact and disinfected grade A eggs. As noted earlier, the reason for
this is that Salmonella enteritidis silently infects the ovaries of healthy
appearing hens and contaminates the eggs before the shells are formed.
Although most infected hens have been found in the northeastern United
States, the infection also occurs in hens in other areas of the country. In the
Northeast, approximately one in 10,000 eggs may be internally contaminated. In
other parts of the United States, contaminated eggs appear less common. Only a
small number of hens seem to be infected at any given time, and an infected hen
can lay many normal eggs while only occasionally laying an egg contaminated with
the Salmonella bacterium.
Who can be infected?
The elderly, infants, and persons with impaired immune systems are at
increased risk for serious illness.
Healthy adults and children are at risk for egg-associated salmonellosis, but
the elderly, infants, and persons with impaired immune systems are at increased
risk for serious illness. In these persons, a relatively small number of
Salmonella bacteria can cause severe illness. Most of the deaths caused by
Salmonella enteritidis have occurred among the elderly in nursing homes.
Egg-containing dishes prepared for any of these high-risk persons in hospitals,
in nursing homes, in restaurants, or at home should be thoroughly cooked and
What is the risk?
In affected parts of the United States, it is estimated that one in 50 average
consumers could be exposed to a contaminated egg each year. If that egg is
thoroughly cooked, the Salmonella organisms will be destroyed and will not make
the person sick. Many dishes made in restaurants or commercial or institutional
kitchens, however, are made from pooled eggs. If 500 eggs are pooled, one batch
in 20 will be contaminated and everyone who eats eggs from that batch is at
risk. A healthy person's risk for infection by Salmonella enteritidis is low,
even in the northeastern United States, if individually prepared eggs are
properly cooked, or foods are made from pasteurized eggs.
What can I do to reduce risk?
Eggs, like meat, poultry, milk, and other foods, are safe when handled
properly. Shell eggs are safest when stored in the refrigerator, individually
and thoroughly cooked, and promptly consumed. The larger the number of
Salmonella present in the egg, the more likely it is to cause illness. To
further prevent the possibility of infection, follow these guidelines:
eggs adequately refrigerated to prevent any Salmonella present in the eggs from
growing to higher numbers, so eggs should be held refrigerated until they are
- 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 enteritidis infections. Both should be consumed promptly and not be
held in the temperature range of 40 to 140 for more than 2 hours.
- Discard cracked or dirty eggs.
- Wash hands and cooking
utensils with soap and water after contact with raw eggs.
- Eat eggs promptly
- Do not keep eggs warm for more than 2hours.
- Refrigerate unused or
leftover egg- containing foods.
- Avoid eating raw eggs (as in homemade ice cream
or eggnog). Commercially manufactured ice cream and eggnog are made with
pasteurized eggs and have not been linked with Salmonella enteritidis
- Avoid restaurant dishes made with raw or undercooked, unpasteurized
eggs. Restaurants should use pasteurized eggs in any recipe (such as Hollandaise
sauce or caesar salad dressing) that calls for pooling of raw eggs.