Listeriosis

Key Features

Essentials of Diagnosis

• Ingestion of contaminated food product

• Undifferentiated fever in a pregnant woman in her third trimester

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

• Obtain blood and cerebral spinal fluid cultures to 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) for 14–21 days

• 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