Listeriosis

1. Overview:

• Definition: Listeriosis is a serious infection caused by Listeria monocytogenes, a gram-positive, facultatively anaerobic bacterium.
• Transmission: Primarily through the ingestion of contaminated food, especially dairy products (unpasteurised soft cheese), ready-to-eat meats, and unwashed vegetables.

2. Epidemiology:

• At-Risk Populations: Pregnant women, neonates, elderly individuals, and immunocompromised patients are particularly susceptible.
• Global Incidence: While rare, listeriosis has a high case-fatality rate, especially in severe cases (meningitis and septicemia).

3. Clinical Presentation:

• Pregnancy-Associated Listeriosis:
  • Often presents with mild flu-like symptoms in the mother but can lead to severe outcomes like miscarriage, stillbirth, preterm labor, or neonatal sepsis.
• Neonatal Listeriosis:
  • Early-Onset: Acquired in utero, leading to sepsis or pneumonia shortly after birth.
  • Late-Onset: Presents as meningitis, usually 2-3 weeks postpartum.
• Listeria Meningitis:
  • Presents with classic signs of bacterial meningitis, but often in older adults or immunocompromised patients.
  • Subacute onset is common, and cranial nerve palsies may be seen.
• Gastrointestinal Form:
  • Fever, myalgia, and Gastroenteritis/ Diarrhea ; typically occurs after consuming contaminated food.
• Sepsis:
  • Particularly in immunocompromised patients, leading to a high mortality rate.

4. Diagnosis:

• Culture: Listeria can be isolated from blood, cerebrospinal fluid (CSF), or amniotic fluid. It grows well on standard agar plates at 37°C and at cold temperatures (cold enrichment).
• Microscopy: Gram-positive rods, often found intracellularly.
• Molecular Tests: PCR can be used for rapid detection, especially in foodborne outbreaks.

5. Management:

• Antibiotic Therapy:
  • First-Line: Ampicillin or penicillin G, often combined with gentamicin for synergistic effects, especially in severe cases (meningitis, septicemia).
  • Alternatives: Trimethoprim-sulfamethoxazole is used for patients allergic to penicillin.
• Pregnancy: Ampicillin is the drug of choice; gentamicin is typically avoided due to potential fetal toxicity.