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For further information, see CMDT Part 35-08: 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 older or immunocompromised patient

  • Blood and cerebrospinal fluid cultures confirm diagnosis

General Considerations

  • Listeria monocytogenes is a facultative, motile, gram-positive rod capable of invading several cell types and causing 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

    • Soft cheeses, such as queso fresco, brie, and ricotta

  • 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 one in five pregnancies complicated by listeriosis result in spontaneous pregnancy loss or stillbirth, and surviving infants are at risk for clinical neonatal listeriosis

    • Granulomatosis infantisepticum

      • Neonatal infection acquired in utero

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

    • Bacteremia with or without sepsis syndrome

      • Seen in neonates or immunocompromised adults

      • Presentation is a febrile illness without a recognized source

    • Meningitis

      • Affects infants under 2 months of age and older adults, ranking third among the common causes of bacterial meningitis

      • Adults with meningitis are usually immunocompromised

      • Cases have been associated with use of glucocorticoids and tumor necrosis factor inhibitors (eg, infliximab)

    • Focal infections occur rarely and include

      • Adenitis

      • Brain abscess

      • Endocarditis

      • Osteomyelitis

      • Arthritis

DIAGNOSIS

  • Positive blood or cerebrospinal fluid culture

  • In meningitis, cerebrospinal fluid often shows a lymphocytic pleocytosis, with variable protein and glucose findings

TREATMENT

  • Tables 32–5 and 32–3

  • 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, 5 mg/kg/day intravenously once or in divided doses

    • Synergistic with ampicillin

    • Combination therapy may be considered during the first few days of treatment to enhance eradication of organisms

  • Trimethoprim-sulfamethoxazole

    • Effective alternative for patients who are allergic to penicillin

    • Dose of trimethoprim component is 10–20 mg/kg/day intravenously divided every 6–12 hours

  • Therapy should be administered for at least 2–3 weeks

  • Longer durations—between 3 and 6 weeks—are recommended for treatment of meningitis, especially in immunocompromised persons

Table 32–3.Initial antimicrobial therapy for purulent meningitis of unknown cause.

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