Listeria monocytogenes
One-Sentence Definition
Listeria monocytogenes is a Gram-positive rod that survives refrigeration and invades host cells, causing foodborne gastroenteritis and life-threatening meningitis/bacteremia in pregnant, elderly, and immunocompromised patients.
Taxonomy & Morphology
- Gram-positive short rods; tumbling motility at room temperature
- Facultative intracellular pathogen; grows at 4 °C (cold enrichment)
- Catalase-positive; β-hemolytic (narrow)
Virulence Highlights
- Internalins (InlA/InlB) — epithelial/placental invasion
- Listeriolysin O (LLO) — escape from phagosome
- ActA — actin-based intracellular motility (cell-to-cell spread)
- Stress survival in food chain (biofilm on equipment)
Clinical Syndromes
- Febrile gastroenteritis (outbreaks)
- Bacteremia, meningoencephalitis (rhombencephalitis)
- Pregnancy: amnionitis, stillbirth, neonatal sepsis (early/late)
Diagnosis
- Blood/CSF culture; cold enrichment for food
- MALDI / biochemicals; PCR panels increasingly include Listeria
- Notify public health for invasive cases
Treatment Notes (conceptual)
- Ampicillin ± gentamicin for synergy in invasive disease (classic regimen logic)
- TMP-SMX alternative in penicillin allergy (confirm local practice)
- Duration longer for meningitis/endocarditis
AMR
- Generally susceptible to ampicillin historically; resistance uncommon but monitored
- Intrinsic resistance patterns differ from other Gram-positives — know local antibiograms
Genomics & Computational Notes
- Outbreak typing: cgMLST / SNP pipelines for food networks
- Stress and virulence islands annotated in WGS (Virulence Factor Databases)
- See Phylogenomics and Outbreak Typing · Clinical WGS Pipelines
Related Notes
- Bacterial Meningitis · Gastrointestinal Infections · Biofilm
- MOCs: MOC - Bacteriology · MOC - Public Health & Epidemiology · MOC - Diseases by System
Active Recall
- Why does cold storage fail as a control for Listeria?
- Which virulence protein mediates phagosomal escape?
- Which patient groups need highest suspicion for invasive listeriosis?