Listeriosis - Causes, Symptoms and Treatment

Definition:

Listeriosis is an infection caused by the weakly hemolytic, gram-positive bacillus Listeria monocytogenes. It occurs most commonly in fetuses, in neonates (during the first 3 weeks of life), older patients, or immunosuppressed adults. This infection produces milder illness in pregnant women and varying degrees of illness in older and immunosuppressed patients; their prognoses depend on the severity of underlying illness.

Causes of Listeriosis

The primary method of person-to-person transmission is neonatal infection in utero (through the placenta) or during passage through an infected birth canal. Other modes of transmission may include inhaling contaminated dust; drinking contaminated, un pasteurized milk; and coming in contact with infected animals, contaminated sewage or mud, or soil contaminated with feces containing L. monocytogenes.

Signs and Symptoms of Listeriosis

Contact with L. monocytogenes commonly causes a transient asymptomatic carrier state, though sometimes it produces bacteremia and a febrile, generalized illness. In pregnant women, especially during the third trimester, listeriosis causes a mild illness with malaise, chills, fever, and back pain. However, the fetus may suffer severe uterine infection, abortion, premature delivery, or stillbirth. Transplacental infection may also cause early neonatal death or granulomatosis infantiseptica, which produces organ abscesses in infants. Infection with L. monocytogenes commonly causes meningitis, resulting in tense fontanels, irritability, lethargy, seizures, and coma in neonates, and low-grade fever and personality changes in adults. Fulminant manifestations with coma are rare.

Diagnosis for Listeriosis

L. monocytoRenes is identified by its diagnostic tumbling motility on a wet mount of the culture. Other supportive diagnostic results include positive culture of blood, spinailluid, drainage from cervical or vaginal lesions, or lochia from a mother with an infected infant - isolation of the organism from these specimens is generally difficult. Listeriosis also causes monocytosis. Differential diagnoses include group B streptococcus infections, congenital syphilis, and toxoplasmosis

Treatment for Listeriosis

The treatment of choice is ampicillin or penicillin I.V. for 3 to 6 weeks, possibly with gentamicin to increase its effectiveness. Alternate treatments include erythromycin, chloramphenicol, tetracycline, or co-trimoxazole.

Ampicillin or penicillin G is best for treating meningitis due to L. monocytogenes because these antibiotics more easily cross the blood-brain barrier.

Pregnant women require prompt, vigorous treatment to combat fetal infection.

Special Considerations and Prevention Tips for Listeriosis

1. Deliver specimens to the laboratory promptly. Because few microbes may be present, take at least 10 ml of spinal fluid for culture.

2. Use secretion precautions until a series of cultures are negative. Be especially careful when handling lochia from an infected mother and secretions from her infant's eyes, nose, mouth, and rectum, including meconium.

3. Evaluate neurologic status at least every 2 hours. In an infant, check fontanels for bulging. Maintain adequate I.V. fluid intake; measure intake and output accurately.

4. If the patient has central nervous system depression and becomes apneic, provide respiratory assistance, monitor respirations, and obtain frequent arterial blood gas measurements.

5. Provide adequate nutrition by total parenteral nutrition, nasogastric tube feedings, or a soft diet, as ordered.

6. Allow parents to see and, if possible, hold their infant in the intensive care unit. Be flexible about visiting privileges. Keep parents informed of the infant's status and prognosis at all times.

7. Reassure parents of an infected newborn who may feel guilty about the infant's illness.

8. Educate pregnant women to avoid infective materials on fanus where listeriosis is endemic among livestock.

Dietary recommendations for prevention of food-borne listeriosis include:

• Thoroughly cooking all raw food from animal sources
• Keeping uncooked meats separate from vegetables and from cooked, ready-to-eat foods
• Washing raw vegetables thoroughly
• Avoiding raw, un pasteurized milk
• Washing hands, cutting boards, and knives after handling uncooked foods.