All pathogenic aerobic gram-negative cocci belong to the Neisseriaceae family, which is composed of 5 genera:

• Acinetobacter
• Kingella
• Moraxella (including 2 subgenera, Moraxella and Branhamella)
• Neisseria
• Oligella

Of these, Neisseria includes the most important human pathogens, N. meningitidis and N. gonorrhoeae. Numerous saprophytic Neisseriaceae commonly inhabit the oropharynx, vagina, or colon but rarely cause human disease. Moraxella catarrhalis causes otitis media in children and sinusitis. Over half a dozen other Moraxella sp and the related Kingella kingae cause infections in the CNS, respiratory tract, urinary tract, endocardium, bones, and joints.

Humans are the only reservoir of Neisseria, and person-to-person spread is the prime mode of transmission. Both N. meningitidis (meningococcus) and N. gonorrhoeae can exist in an asymptomatic carrier state. Carrier states are particularly important with meningococcus because of its association with epidemics. Gonorrhea is discussed in Sexually Transmitted Diseases (STDs): Gonorrhea.

Last full review/revision September 2009 by Carlene A. Muto, MD, MS