Listeriosis is an illness caused by the bacterium
that is acquired by eating contaminated food. The organism can spread to
the blood stream and central nervous system. In women who contract
listeriosis while pregnant, the disease often causes miscarriage or
Listeriosis is caused by an infection with the bacterium
. These bacteria can be carried by many animals and birds, and they have
been found in soil, water, sewage, and animal feed. Five out of every 100
in their intestines. Listeriosis is considered a food-borne illness
because most people are probably infected after eating food contaminated
. However, a woman can pass the bacteria to her baby during pregnancy. In
addition, there have been a few cases where workers have developed
skin infections by touching infected calves or poultry.
In the 1980s, the United States government began taking measures to
decrease the occurrence of listeriosis. Subsequently, processed meats and
dairy products were tested for the presence of
. The Food and Drug Administration (FDA) and the Food Safety and
Inspection Service (FSIS) can legally prevent food from being shipped, or
order food recalls, if they detect any
bacteria. These inspections, in combination with the public education
regarding the proper handling of uncooked foods, appear to be helping.
Nonetheless, as of 2004, about 2,500 individuals become seriously ill from
annually, with about 500 deaths.
Persons at particular risk for listeriosis include the elderly, pregnant
women, newborns, and those with a weakened immune system (called
immunocompromised). Risk is increased when a person suffers from diseases
, kidney disease,
, or by the use of certain medications. Infection is most common in babies
younger than one month old and adults over 60 years of age. Pregnant women
account for 27 percent of the cases, and immunocompromised persons account
for almost 70 percent. Persons with AIDS are 280 times more likely to get
listeriosis than others.
Causes and symptoms
As noted, persons become infected with
by eating contaminated food.
has been found on raw vegetables, fish, poultry, raw (unpasteurized)
milk, fresh meat, processed meat (such as deli meat, hot dogs, and canned
meat), and certain soft cheeses. Listeriosis outbreaks in the United
States since the 1980s have been linked to cole slaw, milk, Mexican-style
cheese, undercooked hot dogs, undercooked chicken, and delicatessen foods.
Unlike most other bacteria,
does not stop growing when food is in the refrigerator; its growth is
merely slowed. Fortunately, typical cooking temperatures and the
pasteurization process do kill this bacteria.
bacteria can pass through the wall of the intestines, and from there they
can get into the blood stream. Once in the blood stream, they can be
transported anywhere in the body but are commonly found the central
nervous system (brain and spinal cord); and in pregnant women they are
often found in the placenta (the organ which connects the baby's
umbilical cord to the uterus).
live inside specific white blood cells called macrophages. Inside
macrophages, the bacteria can hide from immune responses and become
inaccessible to certain
bacteria are capable of multiplying within macrophages and then may
spread to other macrophages.
After people consume food contaminated with this bacteria, they may see
symptoms of infection 11 to 70 days later. Most people do not get any
noticeable symptoms. Scientists suspect that
can cause upset stomach and intestinal problems just like other
food-borne illnesses. Persons with listeriosis may develop flu-like
symptoms such as
nausea and vomiting
, tiredness, and
Pregnant women experience a mild, flu-like illness with fever, muscle
aches, upset stomach, and intestinal problems. They recover, but the
infection can cause miscarriage, premature labor, early rupture of the
birth sac, and stillbirth. Half of the newborns infected with
die from the illness.
There are two types of listeriosis in the newborn baby: early-onset
disease and late-onset disease. Earlyonset disease refers to a serious
illness that is present at birth and usually causes the baby to be born
prematurely. Babies infected during the pregnancy usually have a blood
infection (sepsis) and may have a serious, whole body infection called
granulomatosis infantisepticum. When a full-term baby becomes infected
, that situation is called late-onset disease. Commonly, symptoms of
appear about two weeks after birth. Babies with late-term disease
(inflammation of the brain and spinal tissues); yet they have a better
chance of surviving than those with early-onset disease.
Immunocompromised adults are at risk for a serious infection of the blood
stream and central nervous system (brain and spinal cord). Meningitis
occurs in about half of the cases of adult listeriosis. Symptoms of
listerial meningitis occur about four days after the flu-like symptoms and
include fever, personality change, uncoordinated muscle movement, tremors,
muscle contractions, seizures, and slipping in and out of consciousness.
causes endocarditis in about 7.5 percent of the cases. Endocarditis is an
inflammation of heart tissue due to the bacterial infection. Listerial
endocarditis causes death in about half of the patients. Diseases which
have been caused by
include brain abscess, eye infection, hepatitis (liver disease),
peritonitis (abdominal infection), lung infection, joint infection,
arthritis, heart disease, bone infection, and gallbladder infection.
Listeriosis may be diagnosed and treated by infectious disease specialists
and internal medicine specialists. The diagnosis and treatment of this
infection should be covered by most insurance providers.
The only way to diagnose listeriosis is to isolate
from blood, cerebrospinal fluid, or stool. A sample of cerebrospinal
fluid is removed from the spinal cord using a needle and syringe. This
procedure is commonly called a spinal tap. The amniotic fluid (the fluid
which bathes the unborn baby) may be tested in pregnant women with
listeriosis. This sample is obtained by inserting a needle through the
abdomen into the uterus and withdrawing fluid.
grows well in laboratory media, and test results can be available within
a few days.
Listeriosis is treated with the antibiotics ampicillin (Omnipen) or
sulfamethoxazole-trimethoprim (Bactrim, Septra). Because the bacteria live
within macrophage cells, treatment may be difficult, and the treatment
periods may vary. Usually, pregnant women are treated for two weeks;
newborns, two to three weeks; adults with mild disease, two to four weeks;
persons with meningitis, three weeks; persons with brain abscesses, six
weeks; and persons with endocarditis, four to six weeks.
Scanning electron micrograph (SEM) scan of lysteria monocytogenes.
Patients are often hospitalized for treatment and monitoring. Other drugs
may be provided to relieve
and fever and to treat other reactions to the infection.
The overall death rate for listeriosis is 26 percent. This high death rate
is due to the serious illness suffered by newborns, the elderly, and
immunocompromised persons. Healthy adults and older children have a low
death rate. Complications of
infection include: meningitis, sepsis, miscarriage, stillbirth,
, shock endocarditis, abscess (localized infection) formation, and eye
—A localized collection of pus in the skin or other body tissue
caused by infection.
—A state in which the immune system is suppressed or not
—A large white blood cell that engulfs and digests foreign
invaders, such as bacteria and viruses, in an attempt to stop them from
causing disease within the body.
—An infection or inflammation of the membranes that cover the
brain and spinal cord. It is usually caused by bacteria or a virus.
—A severe systemic infection in which bacteria have entered the
bloodstream or body tissues.
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