The Infectious/Pathogenic Processes Driven by Listeria monocytogenes in Laboratory Mice

Abstract

The term infectious or parasitic disease is used to define a local or systemic pathological state triggered by either viral, bacterial, fungal, or parasitic organisms in the hosts they have passively or actively invaded. Whereas parasites, viruses, and some bacteria, such as Mycobacterium tuberculosis, strictly depend on "their hosts" to achieve their so-called life cycle, other bacterial and fungal microorganisms are entirely independent of animal hosts for proliferation. For example, Listeria monocytogenes are Gram-positive bacteria commonly detected in the external environment, where they live as extracellular organisms. 1 Thus, when L. monocytogenes are isolated from patients in whom local and/or systemic pathogenic processes do develop, they are recognized as "opportunistic bacteria."1 Many different clinical syndromes are initiated by L. monocytogenes in humans who ingested heavily contaminated foods. Invasion by L. monocytogenes may take place at different sites along the digestive tract from its upper part to the intestines. 1 Once Listeria are released within the blood, the various tissues, namely the liver, the spleen, the brain, and the uteroplacental unit, can be invaded. In these sites the bacteria multiply rapidly. Steady-state conditions in the tissues