Overview of Listeria
• It is a small gram positive rod organism.
• Can be isolated from environmental sources such as food stuffs, water, and sewerage
• They can grows on routine media and can sometime be confuse as a contaminant of other organism such as diphtheroids
• Common human pathogen is called Listeria monocytogenes and L. ivanovii (rare)
• Capacity to grow in wide range of temperatures from 4 to 37°C
• Temperature varieties likely accounts for their hardiness and capability to cause refrigerated foods infection.
Precipitating factors:
o Children age 50 years
o Common duringPregnancy
o Immunocompromised patients such as cancer, transplant, AIDS and others
Common site of infection
• CNS: brain abscess, meningitis and also rhomboencephalitis ? rare
• Bacteremia especially pregnant women and elderly adults (for neonatal sepsis)
• Endocarditis include natural or prosthetic valves with a mortality rate of > 40%
• Infections such as lymphadenitis, conjunctivitis, cellulitis, pneumonia, osteomyelitis, pneumonia and septic types
• Gastroenteritis: fever, diarrhea, joint pains ? mostly during contaminated foods outbreaks
• Pregnancy such as bacteremia with either stillbirth or premature delivery
TREATMENT
The role of aminoglycosides base on multiple is still controversial. However, multiple references have documented synergistic benefit with the addition of gentamicin to the therapy mostly in higher risk patients such as immunocompromised, pregnant, children < 1 month with listeria CNS infections and endocarditis.
Also gentamicin dosing for synergy is base a patient to patient specific with a serum peaks and troughs goal of peak 3 to 5 mcg/mL and a trough < 1 mcg/mL added to ampicillin to reach synergy. It is still not perfectly clear if this is necessary.
• Meningitis • Ampicillin 2gm IV every 4-6 hours ? 3weeks
• Ampicillin 2gm IV q4-6h + gentamicin 1.7mg/kg IV q8h x greater than or equal to 3 weeks
Alternatives:
• TMP/SMX 3-5mg/kg (trimethoprim) every 6 h IV x ? 3wks
• Meropenem (Merrem) 2g IV every 8 hours
• Imipenem/cilastatin (Primaxin IV)
• Vancomycin
• Ciprofloxacin
Bacteremia • Ampicillin 2gm IV q4-6h x 2 weeks
• Ampicillin 2gm IV q4-6h + gentamicin 1.7mg/kg IV q8h x 2 weeks
Alternatives:
• TMP/SMX 3-5mg/kg (trimethoprim) every 6 h IV x 2weeks
Brain abscess, Rhomboencephalitis, Cerebritis • Ampicillin 2gm IV q4-6h x 4-6 weeks
• Ampicillin 2gm IV q4-6h + gentamicin 1.7mg/kg IV q8h x 4-6 weeks
Alternatives:
• TMP/SMX 3-5mg/kg (trimethoprim) every 6 h IV x 4-6 weeks
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Gastroenteritis • Ampicillin 2gm IV q4-6h x 7 days
• TMP/SMX 3-5mg/kg (trimethoprim) every 6 hours x 7 days
