Neisseria meningitidis.

N. meningitidis continues to be a worldwide cause of human disease, usually in otherwise healthy individuals. The natural habitat and reservoir for meningococci are the mucosal surfaces of the human nasopharynx and to a lesser extent, the urogenital tract and anal canal. In most instances meningococcal colonization of mucosal surfaces is asymptomatic but may produce local infection. In those individuals who lack serum bactericidal activity against the meningococcus, colonization of mucosal surfaces and bloodstream invasion by N. meningitidis can lead to devastating meningitis and septicemia. Recent studies on the ultrastructure of the meningococcus and on the mechanisms of pathogenesis have given us new insight into meningococcal infections and suggest ways for improved immunoprophylaxis. Currently, penicillin is the drug of choice for the treatment of meningococcal meningitis and septicemia. However, the report of meningococci with antibiotic resistant plasmids is alarming and in the future may alter traditional treatment regimens.