Gram Negative Cocci

1. Neisseria species : The genus Neisseria contains 12 species, two of which, N.meningitidis and N. gonorrhoeae, are commonly pathogenic in humans. Both may cause infections in the CNS, primarily meningitis and meningoencephalitis, but also abscesses, empyemas, and thrombophlebitis.
   

   Neisseria gonorrhoeae (Gram negative diplococci)
   1. N.meningitidis : N. meningitidis (Meningococci) is a gram-negative, nonsporeforming diplococcus. It is a leading cause of fatal bacterial meningitis. Meningitis may be accompanied by appearance of petechiae (rash) that is associated with meningococcal bacteremia (i.e.,meningococemia). Bacteremia leads to thrombocytopenia, disseminated intravascular coagulation, and shock. Less common infections include conjunctivitis, pneumonia, and sinusitis.
   2. N. gonorrhoeae: It is a urogenital pathogen which is transmitted by sexual contacts. Genital infections includes purulent urethritis in males and cerivicitis in female. Other localized infections includes pharyngitis, anorectal infectios, and conjunctivitis (ophthalmia neonatorum). Disseminated gonococcal diseases are pelvic inflammatory disease, bacteremia, arthritis and metastatic infections at other body sites.
2. Moraxella (Branhamella) catarrhalis: Moraxella catarrhalis, a gram negative diplococcus, is an exclusively human pathogen and is a common cause of otitis media in infants and children.  M.catarrhalis causes acute, localized infections such as sinusitis, and bronchopneumonia as well as life-threatening, systemic diseases including endocarditis and meningitis. M. catarrhalis can cause pneumonia, especially in patients with alcoholism or chronic obstructive lung disease. M. catarrhalis also causes exacerbations of chronic obstructive pulmonary disease (COPD) and chronic bronchitis in elderly patients.
3. Veillonella species: They are rarely the sole or predominant organism in sputum smears of patients with pneumonia.