Listeria monocytogenes

Categorization
Cell Wall: Gram Positive Shape: Rod, Non-sporulating
Metabolism: Obligate Anaerobe Life Cycle: Facultative Intracellular
Transmission
  • Adults: Ingestion of contaminated foods
  • Neonates: Mother-to-Child Transmission during birth
Virulence Factors
  • Listeriolysin O (LLO): Allows organisms which have been phagocytosed to rupture phagosomal membrane and enter the cytosol. Furthermore, Listeria can puncture through adjacent cell membranes to move from cell to cell without being exposed to the extracellular environment.
Immunity
  • Cell-mediated immunity is critical for defense against Listeria as it's capacity to exist intracellulary allows it to escape neutralizing antibodies. Therefore, populations with reduced cell-mediated immunity are at risk, especially neonates, immunocompromised patients, and pregnant women.
Clinical Consequences
  • Adults: Listeria can cause sepsis or meningitis in adults, the latter of which may be complicated by encephalitis
  • Neonates: Neonatal meningitis
Treatment
  • First Choices: Ampicillin
  • Additional Choices: Bactrim for those with allergies