Listeriosis is caused by the weakly hemolytic, grampositive bacillus Listeria monocytogenes. It most often occurs in fetuses, in neonates during the first 3 weeks of life, and in older or immunosuppressed adults. The infected fetus usually is stillborn or born prematurely, almost always with lethal listeriosis. This infection produces a milder illness in pregnant women and varying degrees of illness in older or immunosuppressed patients. The prognosis depends on the severity of the underlying disease.
Listeriosis is caused by infection with the germ Listeria monocytogenes, which is found in the soil and in most animals. Listeriosis can be picked up from infected food, particularly pate, certain cheeses, and unwashed fruit and vegetables, including pre-packed salad.
It is also important to have high standards of hygiene when storing, preparing and cooking food.
Symptoms and Signs
Listeriosis causes fever and flu-like symptoms such as fever, muscle aches, and gastrointestinal symptoms such as nausea, vomiting and diarrhea. Symptoms of headache, stiff neck, confusion, loss of balance or convulsions can occur if the infection has spread to the brain or spinal column. Listeria can cause infection of the uterus and cervix, which can result in miscarriages or fetal death especially when the infection has occurred late in pregnancy.
L. monocytogenes is identified by its tumbling motility on a wet mound of the culture. Other supportive diagnostic test results include positive culture of blood, spinal fluid, drainage from cervical or vaginal lesions, or lochia from a mother with an infected infant; however, isolation of the organism from these specimens often is difficult. The proportion of monocytes in the blood also increases.
The patient usually receives l.V. ampicillin or penicillin for 3 to 6 weeks. possibly with gentamicin to increase its effectiveness. Alternative treatments include erythromycin, chloramphenicol, tetracycline, and cotrimoxazole.
Ampicillin and penicillin G. with or without gentamicin, are best for treating meningitis caused by L. monocytogenes because they more easily cross the blood-brain barrier. Pregnant women require prompt, Vigorous treatment to combat fetal infection.
Pregnant women should avoid contact with wild and domestic animals. Listeria is well controlled in American food products, but food-associated outbreaks have occured.
Pregnant women should avoid consumption of soft cheeses, deli meats, and cold salads from salad bars. Foreign food products such as nonpasteurized soft cheeses have also been implicated in outbreaks of listeriosis. Food should always be adequately cooked.
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