I. Epidemiology
  1. Listeria monocytogenes-An intracellular bacterial organism
  2. Found in fresh fruits and vegetables, unpasteurized dairy products, and raw meat (including prepared meats like hot dogs, poultry, and shellfish
  3. Risk factors for Listeria-related illness include immunocompromise and pregnancy
II. Clinical features and diagnosis
  1. Incubation period 6h-10d (mean 24h)
  2. Clinical manifestations can range from asymptomatic infection, to dysentery-like illness with diarrhea and abdominal pain, to CNS infection, ednocarditis, and sepsis
  3. In pregnancy:
    1. Can cause flu-like illness with fever, chills, myalgias, and back pain, most often in the third trimester
    2. Also can be associated with fetal involvement with pustular rash and disseminated infection; may result in miscarriage or stillbirth
    3. Neonatal infection-2 patterns seen
      1. Early-onset (< 5d of age; mean onset 1.5d)-Usually preterm and low birth weight; Lethargy, respiratory distress, fever, rash, jaundice, and/or disseminated granulomata or abscesses can be associated with pneumonia, sepsis, or meningitis; Mortality 20-30%
      2. Late-onset (5-30d of age; mean onset 14.2d)-Usually full-term and normal birth weight; Usually presents with purulent meningitis; Mortality < 20% if treated promptly
  4. Diagnosis
    1. Culture of normally sterile fluids
    2. Stool and vaginal cultures are nonspecific since can be present in those areas in association with asymtpomatic carriage
    3. Gram stain has low sensitivity since usually intracellular
III. Treatment
  1. First line = penicillin, ampicillin, or amoxicillin (work intracellularly; cross placental barrier)
  2. Ampicillin is drug of choice for neonatal infections (often with gentamicin which enhances the bactericidal activity)
  3. If penicillin-allergic, can be treated with trimethoprim/sulfamethoxazole, vancomycin, or erythromycin
  4. Cephalosporins are generally ineffective
  5. Treatment duration in pregnancy is often 3-4wks or until delivery

(Sources include Core Content Review of Family Medicine, 2012)