Other species of the genus Neisseria rarely cause human disease. They are found as part of normal bacterial flora mostly of the respiratory tract. These commensal Neisseria are Neisseria flave-scens, Neisseria sicca, Neisseria lactamica, and Neisseria subflava. Thecommensal Neisseria differ from pathogenic Neisseria species by following properties:
· They can grow on ordinary agar not enriched with blood and serum and they can also grow at 22°C.
· They do not require high percentage of CO2 for their growth.
· They produce greenish yellow or yellow colonies on the media.
N. flavescens and N. sicca have been associated with isolatedcases of meningitis, osteomyelitis, acute otitis media, and acute sinusitis. But true incidence of respiratory tract infection caused by these Neisseria species is not known. Most of these strains are susceptible to penicillins.
N. lactamica is frequently isolated from the nasopharynx andis a nonvirulent Neisseria; however, it is closely related to patho-genicNeisseria.
Neisseria catarrhalis—which was later designated as Branhamella catarrhalis and is now renamed as Moraxella catarrhalis—is a com-mensal of the upper respiratory tract and, occasionally, is found in female genital tract. It is a recognized respiratory opportu-nistic pathogen in immunocompromised host and hospital-ized people. M. catarrhalis is multidrug resistant and grows on ordinary media, such as nutrient agar and MacConkey agar. It causes infections (e.g., otitis media, maxillary sinusitis, menin-gitis, septic arthritis, endocarditis, sepsis, etc.) in immunocom-promised patients and in children. Some strains are susceptible to cephalosporins, chloramphenicol, and tetracycline.