• An infection caused by the ubiquitous, weakly hemolytic, gram-positive bacillus Listeria monocytogenes; pathogenic to many species
  • Occurs most often in fetuses (disseminated infantile listeriosis), neonates, and immunosuppressed patients
  • Most affected adults have preexisting disease (e.g., cirrhosis, lymphomas, solid tumors, AIDS, cancer therapy, organ transplant recipients) or are on corticosteroid therapy.
  • Usual course: acute

Pediatric Considerations

  • Infected fetuses are often stillborn or premature.
  • Up to 50% mortality in treated neonates



  • U.S. foodborne listeriosis: 0.3/100,000 people
  • 2011: A 28-state outbreak from contaminated cantaloupes infected 146 people, with 30 deaths.
  • Particularly affects neonates (<1 month) and elderly (>60 years)
    • Predominant sex: male > female
    • 500 annual deaths from listeriosis in the United States
    • 20–65% of all foodborne infection–related deaths in the United States are due to listeriosis.
    • Pregnant women account for 27% of all Listeria cases and ~60% of cases from ages 10 to 40 years.
    • ~70% of nonperinatal infections occur in immunocompromised patients.
    • Neonates can have early (<7 days) or late-onset (>7 days) infection.
    • Most cases of listeriosis are sporadic (not associated with an outbreak).
    • Listerial meningitis has a mortality rate of 20%.


  • Symptoms ~20 times more likely to manifest in pregnancy
  • Listeriosis is ~300 times more likely in HIV/AIDS patients than in age-matched population.

Etiology and Pathophysiology

  • L. monocytogenes, a small gram-positive bacillus is the primary pathogen; infection with other Listeria species is rare.
  • There are at least 13 serotypes of L. monocytogenes, but most disease is due to types 4b, 1/2 a, and 1/2 b.
  • Incubation period for invasive illness is not well-established and is highly variable because it depends on bacterial load and host immunity.
  • Listeria replicates best at room temperature but can grow at refrigerator temperatures.
  • Listeria has a unique intracellular life cycle.
  • After entering GI tract, Listeria is phagocytosed by active endocytosis and enters host without disturbing the normal GI mucosal structure.
  • Hematogenous dissemination occurs through the bloodstream; crosses placental and blood–brain barriers
  • Illness begins 2 to 70 days after contaminated food consumption.
  • Extremely common in food supply: Listeria recovered from 15–70% of raw vegetables, fish, meat, ice cream, and unpasteurized milk
    • Deli meat is the highest risk ready-to-eat food source for L. monocytogenes; retail-sliced deli meats have higher rates than prepackaged.
  • Isolated in stool of 5% of asymptomatic adults
  • Resistance to Listeria infection is cell-mediated.

Risk Factors

  • Age: fetus, neonate, elderly
  • Metastatic malignant disease
  • HIV infection; alcoholism
  • Renal hemodialysis
  • Immunosuppression (including corticosteroid therapy)
  • Exposure to infected animals (veterinarians, butchers); animal-to-human transmission is rare.
  • Ingesting contaminated food or drink (soft cheeses, milk, butter, pate, cold-smoked trout, hot dogs, ready-to-eat pork, and deli meats)
  • Pregnancy; fetal and neonatal disease have high mortality; difficult to diagnose in pregnancy because patients are often asymptomatic or present with a flulike illness; requires prompt treatment to prevent fetal transfer
  • Use of proton pump inhibitors
  • Prior to hospitalization; 40% of cases exposed to high-risk foods during hospitalization (1)[C]
  • Colonoscopy

General Prevention

  • Counseling of pregnant women regarding the increased risk of listeriosis during pregnancy
  • for updates on recalled foods
  • Avoid handling livestock.
  • Avoid contaminated silage and sewage.
  • Avoid raw/unpasteurized dairy products.
  • Avoid soft cheeses (Mexican and feta).
  • Wash all raw vegetables carefully.
  • Wash hands after handling uncooked foods.
  • Cook leftovers, hot dogs, cold cuts, and deli meats adequately before eating.
  • Listeriosis can be effectively prevented with trimethoprim-sulfamethoxazole in organ transplant and AIDS patients (2)[B].

Commonly Associated Conditions

  • Pregnancy
  • Immunodeficiency; diabetes
  • Cirrhosis; hemochromatosis and iron overload (Iron is a virulence factor for Listeria.)
  • Lymphoma; leukemia
  • Solid tumors; organ transplant recipients
  • Chronic renal disease
  • Alcoholism
  • Age >60 years

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