The Neisseria

Introduction

The genus Neisseria includes a group of closely related Gram-negative diplococci that are primarily commensal organisms of the mucous membranes of mammals (Knapp, 1988a). Several Neisseria spp. are opportunistic pathogens causing disease in immunocompromised hosts. Two species, N. gonorrhoeae (the gonococcus) and N. meningitidis (the meningococcus), are important human pathogens.

Phylogeny

Species Groups

While the 1994 edition of [{http://www.cme. msu.edu/bergeys}Bergey's Manual of Determinative Bacteriology] lists 13 species within the genus, the systematics of Neisseria have been problematic, and strains have been frequently reclassified as new techniques have become available. DNA-DNA hybridization techniques, numerical taxonomy procedures (Barrett and Sneath, 1994) and sequence analysis of various genes (Smith et al., 1999) have divided the Neisseria into two subgroups: 1) the closely related pathogens N. gonorrhoeae and N. meningitidis, a related