Listeria monocytogenes meningitis: an opportunistic infection.

Meningitis caused by L. monocytogenes is discussed from the standpoints of clinical presentation and course, underlying illness, and altered host resistance. The `opportunistic' nature of the infection is emphasized, and case histories of patients with diseases which may specifically alter host resistance in such a fashion as to render the patient susceptible to this organism, or who are receiving drugs which may have the same result, are presented. The critical role of host macrophages, and the alteration of this role by Hodgkin's disease, leukaemia, and cytotoxic drug therapy are emphasized.