Definition

Salmonella food poisoning is a bacterial food poisoning
caused by the Salmonella bacterium. It results in
the swelling of the lining of the stomach and intestines
(gastroenteritis). While domestic and wild animals,
including poultry, pigs, cattle, and pets such as turtles,
iguanas, chicks, dogs, and cats can transmit this illness,
most people become infected by ingesting foods contaminated
with significant amounts of Salmonella.

Description

Salmonella food poisoning occurs worldwide, however
it is most frequently reported in North America and
Europe. Only a small proportion of infected people are
tested and diagnosed, and as few as 1% of cases are actually
reported. While the infection reate may seem relatively
low, even an attack rate of less than 0.5% in such a
large number of exposures results in many infected individuals.
The poisoning typically occurs in small, localized
outbreaks in the general population or in large outbreaks
in hospitals, restaurants, or institutions for children
or the elderly. In the United States, Salmonella is
responsible for about 15% of all cases of food poisoning.
Improperly handled or undercooked poultry and eggs
are the foods which most frequently cause Salmonella
food poisoning. Chickens are a major carrier of Salmonella
bacteria, which accounts for its prominence in poultry
products. However, identifying foods which may be contaminated
with Salmonella is particularly difficult because
infected chickens typically show no signs or symptoms.

Since infected chickens have no identifying characteristics,
these chickens go on to lay eggs or to be used as meat.
At one time, it was thought that Salmonella bacteria
were only found in eggs which had cracked, thus allowing
the bacteria to enter. Ultimately, it was learned that,
because the egg shell has tiny pores, even uncracked eggs
which sat for a time on a surface (nest) contaminated
with Salmonella could themselves become contaminated.
It is known also that the bacteria can be passed from the
infected female chicken directly into the substance of the
egg before the shell has formed around it.

Anyone may contract Salmonella food poisoning,
but the disease is most serious in infants, the elderly, and
individuals with weakened immune systems. In these
individuals, the infection may spread from the intestines
to the blood stream, and then to other body sites, causing
death unless the person is treated promptly with antibiotics.
In addition, people who have had part or all of their
stomach or their spleens removed, or who have sickle
cell anemia, cirrhosis of the liver, leukemia, lymphoma,
malaria, louse-borne relapsing fever, or Acquired
Immunodeficiency Syndrome (AIDS) are particularly
susceptible to Salmonella food poisoning.

Causes and symptoms

Salmonella food poisoning can occur when someone
drinks unpasteurized milk or eats undercooked chicken
or eggs, or salad dressings or desserts which contain raw
eggs. Even if Salmonella-containing foods such as chicken
are thoroughly cooked, any food can become contaminated during
preparation if conditions and equipment for
food preparation are unsanitary.

Other foods can then be accidentally contaminated if
they come into contact with infected surfaces. In addition,
children have become ill after playing with turtles
or iguanas, and then eating without washing their hands.
Because the bacteria are shed in the feces for weeks after
infection with Salmonella, poor hygiene can allow such a
carrier to spread the infection to others.

Symptoms appear about one-two days after infection,
and include fever (in 50% of patients), nausea and
vomiting, diarrhea, and abdominal cramps and pain.
The diarrhea is usually very liquid, and rarely contains
mucus or blood. Diarrhea usually lasts for about four
days. The illness usually ends in about five-seven days.
Serious complications are rare, occurring most often
in individuals with other medical illnesses. Complications
occur when the Salmonella bacteria make their way
into the bloodstream (bacteremia). Once in the bloodstream,
the bacteria can enter any organ system throughout
the body, causing disease. Other infections which can
be caused by Salmonella include: