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. monocyto-
genesare normally present in soil and can contami-
nate milking equipment. Animals also can carry L.
monocytogeneswithout illness. The most common
sources of listeriosis are unpasteurized milk and
cheeses and processed foods that become contami-
nated after processing, such as lunch meats served
in delis and restaurants. Thorough cooking and
pasteurization kill L. monocytogenesBACTERIA.

Symptoms and Diagnostic Path
Symptoms of listeriosis are often fairly severe and
many people who develop the illness require hos-
pitalization for treatment. Symptoms may include

• FEVER


• difficulty BREATHING(DYSPNEA)


• NAUSEAand VOMITING


• MUSCLEaches and JOINT PAIN

Symptoms may also be specific to the type of
infection, such as MENINGITISor PNEUMONIA. The
diagnostic path includes BLOODcultures and, when
neurologic symptoms are present, LUMBAR PUNCTURE
to examine and culture the spinal fluid. The pres-
ence of L. monocytogenesconfirms the diagnosis.

Treatment Options and Outlook

Treatment is antibiotic therapy, intravenous when
symptoms are serious and oral when symptoms
are moderate. Ampicillin, erythromycin, and sul-
famethoxazole/trimethoprim (SMZ-TMP) are the
antibiotics most effective; the usual course of
antibiotic therapy may be four to six weeks. Most

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 vulnera-

ble 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. Listerio-

sis 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 thor-

oughly 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. monocytogenesinfection.

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 scapularistick, com-

mon 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

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