Pili of Neisseria meningitidis: an electron microscopic study on their occurrence, related to different strain characteristics.

The occurrence of pili has been assessed for 85 strains of Neisseria meningitidis belonging to different serogroups and serotypes, isolated from nasopharyngeal carriers and patients with acute disease. The evolution of piliation on multiple subcultivation has been followed for 16 strains. Almost all the strains were piliated, regardless of their origin, serogroup or serotype. Piliation was generally maintained, although to a variable extent, through more than 50 passages. Type, regulation and possible function in vivo of the described pili are discussed.