Listeria monocytogenes

Snapshot

• A 73-year-old woman is brought to the emergency room by family members due to intense headache, subjective fever, and altered mental status. She currently lives in an independent living facility and enjoys eating charcuterie and cheese plates. On physical exam, she is oriented to person and place, but not time, a change from her mental baseline, and found to have nuchal rigidity. A lumbar puncture is done and the cerebral spinal fluid is sent for studies. In the meantime, she is started empirically on ceftriaxone, vancomycin, and ampicillin.

Introduction

• Classification
  • Listeria monocytogenes 
    • a facultative intracellular, aerobic, catalase-positive gram-positive bacillus 
    • transmission 
      • ingestion of unpasteurized dairy products or cold deli meats
      • transplacental vertical transmission
      • vaginal transmission during birth to neonate
    • clinical syndromes
      • amnionitis
      • septicemia
      • spontaneous abortion
      • granulomatosis infantiseptica
      • meningitis
        • neonates
        • immunocompromised patients
      • gastroenteritis
        • immunocompetent patients
• Epidemiology
  • incidence
    • rare
  • demographics
    • neonates
    • elderly
    • pregnant women
  • risk factors
    • eating unpasteurized products and deli meat
    • immunocompromised status
    • older age
• Pathogenesis
  • the bacteria move from cell-to-cell across cell membranes via actin polymerization
    • avoids antibody attack
  • toxin listeriolysin O forms pores in host phagosomes to promote intracellular replication 
  • 3^rd trimester pregnant women are most susceptible due to T-cell immunity impairment
• Prevention
  • avoidance of unpasteurized products and deli meats in pregnant women
• Prognosis
• mortality is 20-50% in central nervous system infections

Presentation

• Gastroenteritis
  • nausea
  • vomiting
  • fever
  • headache
• Meningitis 
  • fever
  • headache
  • altered mental status
• Infection in a pregnant woman
  • flu-like syndrome or gastroenteritis
  • premature labor
  • spontaneous abortion
• meningitis or sepsis in the neonate

Imaging

• Brain computed tomography (CT)
  • indication
    • all patients
    • evaluate for abscesses
  • findings
    • often normal
• may have hydrocephalus

Studies

• Labs
  • cerebrospinal fluid (CSF) studies
    • neutrophil-dominant pleocytosis
    • elevated protein
    • low or normal glucose
    • gram-positive or gram-variable rods
    • positive culture 
  • blood culture
  • tumbling motility in broth at 22°C 
• Making the diagnosis
• based on clinical presentation and laboratory studies

Differential

• Neisseria meningitis 
  • distinguishing factors
    • CSF Gram stain would show gram-negative diplococci
    • patients often present with a petechial rash
• however, treatment regimen should include ampicillin empirically if Listeria is suspected in a patient with meningitis

Treatment

• Medical
  • ampicillin
    • indication
      • first-line
  • trimethoprim-sulfamethoxazole
    • indication
• second-line

Complications

• Seizures
• Fetal loss