Monday, August 17, 1998

1. Provided by David Mann, Division of Outbreak Investigation, Maryland Department of Health and Mental Hygiene.

From August 7, 1998 to August 14, 1998 five outbreaks were reported to the Maryland Department of Health and Mental Hygiene. From long term care facilities: one outbreak of Varicella. Foodborne outbreaks: three outbreaks of food service facility-associated gastroenteritis of unknown etiology. One outbreak of food service facility-associated gastroenteritis due to Salmonella group D.

2. The Johns Hopkins Hospital. Information provided by Dr. May Arroyo, Department of Pathology.

Case presentation: A 50 year old male was in his usual state of good health until two days prior to admission at which time, on returning from work, he complained of severe headache and went to sleep. The patient was awoken two days later by his wife who noted that he appeared disoriented and combative. He was taken by paramedics to an outside hospital where a CT scan was performed an interpreted as suspicious for subarachnoid hemorrhage. The patient was transferred to The Johns Hopkins Hospital for neurosurgical evaluation. In the ED, the patient suffered a seizure and five minutes of ventricular tachycardia. A pre-intubation arterial blood gas revealed a pH of 6.96. The patient was febrile and a lumbar puncture demonstrated an opening pressure of greater than 30 mm H₂O, cloudy fluid, 386 mg/dl protein, 291 mg/dl glucose, 968 red blood cells/mm³, and 8400 white blood cells/mm³ with 90% neutrophils. The CSF was negative for H. influenzae, S. pneumoniae, group B Streptococcus, or N. meningitidis. The peripheral blood contained 34,600/mm³ white blood cells with a differential of 7% lymphocytes, 8% monocytes, 81% neutrophils, and 4% bands. The patient was started on broad spectrum antibiotics while awaiting identification of the organism. The patient's past medical history is significant for hypertension, diabetes mellitus (type II), sarcoid, cirrhosis, status post splenectomy.

Organism: The CSF culture grew Listeria monocytogenes. Moreover L. monocytogenes was also isolated from the blood cultures drawn at the outside hospital. Listeria is a beta-hemolytic , catalase positive, facultative anaerobic, non-sporulating, non-acid fast, small, gram positive rod. Sixteen serotypes of L. monocytogenes have been identified based on the somatic and flagellar antigens. However, only three serotypes are associated with disease in humans, making serotyping uninformative. Listeria can grow both intracellularly and extracellularly.

The organism is ubiquitous. In humans, infection is generally acquired through ingestion of contaminated food products including raw fruits and vegetables, soft cheeses, unpasteurised cheese or milk, undercooked chicken, fish, or red meat, and meat products. Neonatal listeriosis is acquired by transplacental infection or ascending infections from the vagina.

Clinical presentation: The incubation period of listeriosis is approximately 3 to 4 weeks. Persons at increased risk of acquiring listeriosis include infants, pregnant women, elderly, immunosuppressed individuals, and chronic and debilitating individuals. The latter includes individuals with underlying medical conditions such as malignancy, HIV infection, heart disease, diabetes mellitus, renal disease, alcoholic and non-alcoholic liver disease, and collagen-vascular disease. As many as 30% of adult patients with listeriosis are immunocompetent (2).

In children and adults listeriosis generally presents as purulent meningitis or septicemia. Other CNS manifestations include brain abscess, meningoencephalitis, cerebritis, and spinal cord abscesses. Listeriosis involving the CNS generally presents as ataxia, tremors, seizures, coma, or nuchal rigidity with fever, or as focal neurological signs localizing to the brainstem in the absence of meningeal signs.. The CSF reveals a high polymorphonuclear leukocytosis. The CSF protein level is generally elevated, however the glucose level is normal in 60% of patients (2). The mortality rate is approximately 90% in untreated patients and 30% in patients receiving therapy (3). Review of the literature indicates that L. monocytogenes is the causative agent in 8% of cases of bacterial meningitis in adults (2).

Less commonly, listeriosis may manifest as a focal infection presumably resulting from seeding following a transient bacteremia. Focal infections include endophthalmitis, skin infection, osteomyelitis, septic arthritis, liver abscess, cholecystitis, pneumonitis, and peritonitis (2).

Pregnant women usually develop a self-limiting illness consisting of a flu-like illness with fever, headache, and vomiting. In utero infection of the fetus may result in in utero fetal demise or a premature infected fetus with respiratory distress and widely disseminated abscesses and granulomas in many organs, generally referred to as granulomatosis infantiseptica or early neonatal listeriosis. Histopathologic examination of the placenta reveals macroabscesses consisting of necrotic villi accompanied by an exuberant acute inflammatory reaction (1,2). Late-onset neonatal listeriosis, presumably acquired postpartum, becomes apparent several days to several weeks after birth. The clinical manifestation is generally meningitis.

Serological tests are not useful in the diagnosis of listeriosis, given the cross-reactivity of certain L. monocytogenes antigens with other gram positive organisms (2).

Treatment: The treatment of choice for listeriosis is ampicillin or penicillin G in combination of with an aminoglycoside. Three weeks of antimicrobial therapy are recommended. Other options include tobramycin, erythromycin, and co-trimoxazole. Cephalosporins, chloramphenicol, tetracycline, minocycline, or trimethoprin are not effective against listeriosis (1).

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