Neisseria

Neisseria is a large genus of bacteria that colonize the mucosal surfaces of many animals. Of the 11 species that colonize humans, two are pathogens, N. meningitidis and N. gonorrhoeae, which cause meningitis and gonorrhea, respectively.
The bacteria is most prevalent in young individuals, especially in dorms, but only about 1% of the infected population will develop meningitis.