Sunday 30 November 2003
Listeria monocytogenes is a Gram-positive, motile facultative intracellular bacterium that causes severe food-borne infections.
Miniepidemics of L. monocytogenes have been linked to dairy products, chicken, and hot dogs. Pregnant women, their neonates, the elderly, and immunosuppressed persons (e.g., transplant recipients or AIDS patients) are particularly susceptible to severe L. monocytogenes infection.
In pregnant women (and pregnant sheep and cattle), L. monocytogenes causes an amnionitis that may result in abortion, stillbirth, or neonatal sepsis.
In neonates, L. monocytogenes may cause disseminated disease (granulomatosis infantiseptica) and an exudative meningitis, both of which are also seen in immunosuppressed adults.
L. monocytogenes has leucine-rich proteins on its surface called internalins, which bind to E-cadherin on host epithelial cells and induce internalization of the bacterium.
Inside the cell, the bacteria escape from the membrane-bound phagolysosome by the action of a pore-forming protein, listeriolysin O, and two phospholipases.
In the host cell cytoplasm, ACTA, a bacterial surface protein, binds to host cell cytoskeletal proteins and induces actin polymerization, which propels the bacteria into adjacent, uninfected host cells.
Resting macrophages, which internalize L. monocytogenes through C3 activated on the bacterial surface, fail to kill the bacteria. In contrast, macrophages that are activated by IFN-γ phagocytose and kill the bacteria.
Hence, unlike most other Gram-positive bacteria, protection against L. monocytogenes is mediated largely by IFN-γ produced by NK cells and T cells.
Listeria monocytogenes infection
Cossart P, Pizarro-Cerda J, Lecuit M. Invasion of mammalian cells by Listeria monocytogenes: functional mimicry to subvert cellular functions. Trends Cell Biol. 2003 Jan;13(1):23-31. PMID: #12480337#
Lecuit M, Cossart P. Genetically-modified-animal models for human infections: the Listeria paradigm. Trends Mol Med. 2002 Nov;8(11):537-42. PMID: #12421688#