Listeria monocytogenes - Listeriosis

Diagnosis

Indications for Testing

High level of suspicion coupled with symptoms in at-risk patients

Laboratory Testing

• CDC – diagnosis and testing recommendations
• Rapid detection tests may be available (monoclonal antibodies or nucleic acid hybridization) but may only identify genus Listeria
• Culture
  • Blood
  • Cerebrospinal fluid (CSF)
  • Amniotic fluid
  • Maternal/fetal tissues

Differential Diagnosis

• Diarrhea, caused by other agents of gastroenteritis (viral, bacterial, parasitic)
• Toxoplasmosis
• Encephalitis
• Meningitis
• Vasculitis

Background

Epidemiology

Prevalence – ~1,600 people/year in U.S. (CDC, 2016)

Organism

• Gram-positive facultative, intracellular rods
• Hardy organism – capable of growing at both 4ºC and 37ºC
• Motile by means of flagella at room temperature, but not at 37ºC (body temperature); can spread from cell to cell via actin polymerization
• The only recognized human pathogen in Listeria species; has >14 serotypes​
• Infection usually follows consumption of contaminated food (listeria can grow and multiply in a refrigerated state)
  • Uncooked meats and vegetables
  • Unpasteurized milk and cheeses
  • Processed foods (eg, soft cheeses, processed meats, smoked seafood)

Risk Factors

• Immunocompromised state as a result of
  • Corticosteroids
  • Transplant drugs
  • Cancer
  • HIV/AIDS
• Chronic diseases
  • Alcohol abuse/chronic liver disease
  • Diabetes mellitus
  • Renal disease
• >65 years
• Pregnancy

Clinical Presentation

• Initial symptoms – fever, muscle aches, nausea, diarrhea
• Localized infection
  • Skin
  • Intra-abdominal
• More serious symptoms (may develop if infection spreads)
  • Systemic sepsis
  • Central nervous system (CNS) infection
    • Meningitis
    • Encephalitis
• Manifestations in pregnancy
  • Sepsis in mother and newborn
  • Spontaneous or septic abortion
  • Stillbirth