All patients with listeriosis require antibiotic therapy. Ampicillin, with or without gentamicin, is the antibiotic of choice for the treatment of listeriosis. Patients intolerant to penicillins may be managed with trimethoprim-sulfamethoxazole. Duration of therapy depends on the clinical syndrome and may range from several days in non-complicated gastroenteritis to 6 weeks in endocarditis or encephalitis. Listerial gastroenteritis is frequently self-limited among healthy adults, but a short course of oral ampicillin may be considered among immunocompromised or pregnant individuals or those who have ingested food implicated in outbreaks. Non-gastroenteritis listeriosis often require hospitalization and intravenous (IV) antibiotic therapy.

• Either Ampicillin, amoxicillin, or penicillin G is effective for the treatment of listeriosis.
• Addition of an aminoglycoside, which confers synergistic bactericidal effects to ampicillin, is recommended for the treatment of listerial bacteremia, endocarditis, brain abscess, meningitis, or rhombencephalitis.^[1]
• Alternatively, for patients unable to tolerate beta-lactams, trimethoprim-sulfamethoxazole may be administered.

• The table below describes the recommended duration of therapy based upon the clinical syndrome:^[2][3]

• 1. Meningitis ^[4]

• Preferred regimen: Ampicillin 2g IV q4-6h ± Gentamicin 1.7 mg/kg IV q8h for more than 3 weeks
• Alternative regimen: TMP-SMX 3-5 mg/kg (trimethoprim) IV q6h for more than 3 weeks

• 2. Bacteremia

• Preferred regimen: Ampicillin 2g IV q4-6h ± Gentamicin 1.7 mg/kg IV q8h for 2 weeks
• Alternative regimen: TMP-SMX 3-5 mg/kg (trimethoprim) q6h IV for 2 weeks

• 3. Brain abscess or rhomboencephalitis

• Preferred regimen: Ampicillin 2g IV q4-6h ± Gentamicin 1.7 mg/kg IV q8h for 4-6 weeks
• Alternative regimen: TMP-SMX 3-5 mg/kg (trimethoprim) q6h IV for 4-6 weeks

• 4. Gastroenteritis

• Preferred regimen (1): Amoxicillin 2g IV q4-6h
• Preferred regimen (2): TMP-SMX 3-5 mg/kg (trimethoprim) q6h IV for 7 days