What antibiotic is typically used to treat listeria infections?

Treatment of Listeria Infections

Ampicillin or amoxicillin is the first-line antibiotic treatment for listeriosis, with trimethoprim-sulfamethoxazole as the preferred alternative for penicillin-allergic patients. 1, 2

First-Line Treatment Options

Standard Treatment

• Ampicillin: 2g IV every 4 hours for 21 days 1
  • FDA-approved for Listeria monocytogenes infections 2
  • Penetrates the blood-brain barrier when meninges are inflamed 2
• Amoxicillin: 2g IV every 4 hours (equivalent alternative to ampicillin) 1

Combination Therapy Considerations

• Historically, gentamicin was added to ampicillin for synergistic effect 3, 4
• Current guidelines no longer routinely recommend adding gentamicin 1

Alternative Treatments (Penicillin Allergy)

• Trimethoprim-sulfamethoxazole: 10-20 mg/kg/day of trimethoprim component in divided doses 1
  • Excellent alternative with good CSF penetration 4
• Erythromycin: Option for pregnant women with penicillin allergy 4, 5
• Vancomycin: Appropriate for primary bacteremia but has poor CSF penetration 4

Important Treatment Considerations

Duration of Therapy

• Minimum 21 days for invasive infections 1
• Bacteremia: 1-2 weeks of therapy 4
• Meningitis: Typically 20+ days 4
• Endocarditis: 6-8 weeks 4

Special Populations

Pregnant Women

• Ampicillin or amoxicillin preferred 5, 1
• Erythromycin if penicillin-allergic 5, 4
• Fluoroquinolones should be avoided 5
• Prompt treatment essential as listeriosis can lead to pregnancy loss 1

Immunocompromised Patients

• May require longer treatment courses 1
• Closer monitoring for treatment failure 1

Neonates

• Ampicillin/amoxicillin 50 mg/kg every 8 hours 1

Critical Warnings

Antibiotics to Avoid

• Cephalosporins: No activity against Listeria - intrinsically resistant 1, 3, 6
• Fluoroquinolones: Generally not recommended as first-line therapy 6, 7
• Fosfomycin: Ineffective against Listeria 6, 7

Monitoring Recommendations

• Daily clinical assessment for fever and neurological symptoms 1
• Repeat blood cultures to document clearance 1
• Consider repeat lumbar puncture to document CSF sterilization in meningitis cases with poor clinical response 1
• Monitor for adverse effects of antibiotics, especially in immunocompromised patients 1

Diagnostic Considerations

• Blood cultures (sensitivity 10-75%) should be obtained before starting antibiotics 1
• Lumbar puncture should be performed in all patients with Listeria bacteremia to rule out meningitis 1
• If dexamethasone was started for suspected bacterial meningitis, discontinue once Listeria is identified 1

Listeriosis carries a high mortality rate, particularly in immunocompromised patients, making prompt and appropriate antibiotic therapy essential for improving outcomes 3, 8.