Inflammation of the meninges caused by listeria monocytogenes infection, usually occurring in individuals under the age of 3 years or over the age of 50 years. It may occur at any age in individuals with immunologic deficiency syndromes. Clinical manifestations include fever, altered mentation, headache, meningeal signs, focal neurologic signs, and seizures. (From Medicine 1998 Sep;77(5):313-36)