Encyclopedia of Health and Medicine

L–M
listeriosis An illness that results from INFECTION
with the bacterium Listeria monocytogenes. Listeriosis
most often occurs as a foodborne illness and has the
potential to cause serious symptoms. L. monocytogenes
are normally present in soil and can contaminate
milking equipment. Animals also can carry L.
monocytogenes without illness. The most common
sources of listeriosis are unpasteurized milk and
cheeses and processed foods that become contaminated
after processing, such as lunch meats served
in delis and restaurants. Thorough cooking and
pasteurization kill L. monocytogenes BACTERIA.
Symptoms and Diagnostic Path
Symptoms of listeriosis are often fairly severe and
many people who develop the illness require hospitalization
for treatment. Symptoms may include
• FEVER
• difficulty BREATHING (DYSPNEA)
• NAUSEA and VOMITING
• MUSCLE aches and JOINT PAIN
Symptoms may also be specific to the type of
infection, such as MENINGITIS or PNEUMONIA. The
diagnostic path includes BLOOD cultures and, when
neurologic symptoms are present, LUMBAR PUNCTURE
to examine and culture the spinal fluid. The presence
of L. monocytogenes confirms the diagnosis.
Treatment Options and Outlook
Treatment is antibiotic therapy, intravenous when
symptoms are serious and oral when symptoms
are moderate. Ampicillin, erythromycin, and sulfamethoxazole/trimethoprim
(SMZ-TMP) are the
antibiotics most effective; the usual course of
antibiotic therapy may be four to six weeks. Most
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people fully recover with appropriate ANTIBIOTIC
MEDICATIONS.
Risk Factors and Preventive Measures
People most at risk for listeriosis are those who are
IMMUNOCOMPROMISED, particularly people who have
HIV/AIDS. Pregnant women are also more vulnerable
to infection and can pass the infection to their
unborn babies; researchers believe this is due to
the changes that take place in a woman’s body
under the influence of the hormones of
PREGNANCY. Some pregnant women can harbor L.
monocytogenes bacteria without becoming ill,
though pass the infection to their babies. Listeriosis
can cause STILLBIRTH (fetal death) and serious
neurologic problems in newborns after birth.
Health experts caution pregnant women (and
other people at increased risk for listeriosis) to eat
lunch meats and hot dogs only that are thoroughly
reheated, to eat only pasteurized cheeses,
to drink only pasteurized milk, and to wash all
vegetables and fruits before eating them including
lettuce) as methods for reducing their exposure to
L. monocytogenes infection.
See also FOODBORNE ILLNESSES; FOOD SAFETY; HOR-
MONE; WATERBORNE ILLNESSES.
Lyme disease An illness that results from INFEC-
TION with the bacterium Borrelia burgdorferi in
North America and other Borrelia species in
Europe. The bite of the Ixodes scapularis tick, common
in wooded areas throughout the northern
United States, spreads the infection. B. burgdorferi
infection primarily causes flulike symptoms
though may also affect the CENTRAL NERVOUS
SYSTEM, cardiovascular system, and the joints.
Symptoms of Lyme disease begin 5 to 30 days
after a tick bite, typically with a characteristic RASH