Neisseria

• Genus of Gram-negative diplococci within the family Neisseriaceae
• Non-motile, non-spore-forming, oxidase-positive and mostly catalase-positive
• They are commensal flora of the mucosal membranes of humans and some animals, and are generally considered non-pathogenic except Neisseria meningitidis and Neisseria gonorrhoeae
• Species include:
  • Neisseria meningitidis
  • Neisseria gonorrhoeae
  • Neisseria lactamica has resports of bacteremia and pneumonia in immucompromised patients
  • Neisseria cinerea has been isolated from cervix, rectum, conjunctivae, blood, and CSF, and rare cases of peritonitis, tonsillitis, lymphadenitis, proctitis, and pulmonary cavitations
  • Neisseria flavescens and Neisseria polysaccharea are in the flora of human respiratory tract and re non-pathogenic
  • Nesseria subflava, Neisseria flava, Neisseria perflava, Neisseria mucosa, and Neisseria sicca are in the flora of human respiratory tract and can rarely cause endocarditis, bacteremia, meningitis, pneumonia, empyema, pericarditis, peritonitis, septic arthritis, and liver abscess
  • Neisseria elongata and Neisseria weaveri, in contrast to the other species, are bacilli in pairs or chains, and are catalase-negative
    • Neisseria elongata is found in the human respiratory tract, and can rarely cause endocarditis, bacteremia, ad osteomyelitis
    • Neisseria weaveri is found in the canine respiratory tract, and can rarely cause pneumonia