Listeriosis

Key Features

Essentials of Diagnosis

• Ingestion of contaminated food product

• Fever in a pregnant woman in her third trimester

• Altered mental status and fever in an elderly or immunocompromised patient

• Blood and cerebral spinal fluid cultures confirm diagnosis

General Considerations

• Listeria monocytogenes is a facultative, motile, gram-positive rod that is capable of invading several cell types and causes intracellular infection

• Most cases of infection are sporadic, but outbreaks have been traced to eating contaminated food, including

  • Unpasteurized dairy products

  • Hot dogs

  • Delicatessen meats

  • Cantaloupes

  • Ricotta cheese

• Outbreaks have been associated with significant morbidity and mortality in infected persons

Clinical Findings

• Five types of infection are recognized

  • Infection during pregnancy

    • Usually in the last trimester

    • Produces a mild febrile illness without an apparent primary focus and may resolve without therapy

    • However, approximately 1 in 5 pregnancies complicated by listeriosis result in spontaneous abortion or stillbirth and surviving infants are at risk for clinical neonatal listeriosis

  • Granulomatosis infantisepticum

    • Neonatal infection

    • Characterized by disseminated abscesses and granulomas and a high mortality rate

  • Bacteremia with or without sepsis syndrome

    • An infection of neonates or immunocompromised adults

    • Presentation is a febrile illness without a recognized source

  • Meningitis

    • Affects infants younger than 2 mo and adults, ranking third among the common causes of bacterial meningitis

    • Adults with meningitis are usually immunocompromised

    • Cases have been associated with HIV infection

  • Focal infections occur rarely and include

    • Adenitis

    • Brain abscess

    • Endocarditis

    • Osteomyelitis

    • Arthritis

Diagnosis

• Positive blood or cerebrospinal fluid culture

• In meningitis, cerebrospinal fluid shows a neutrophilic pleocytosis

Treatment

• Tables 30–4 and 30–2

• Drug of choice is ampicillin, 8–12 g/day intravenously in four to six divided doses (the higher dose is recommended in cases of meningitis)

• Gentamicin at 5 mg/kg/day once or in divided doses intravenously is synergistic with ampicillin; combination therapy may be considered during the first few days of treatment to enhance eradication of organisms

• Trimethoprim-sulfamethoxazole

  • An effective alternative for patients who are allergic to penicillin

  • The dose of trimethoprim component is 10–15 mg/kg/day