ABSTRACT
The genus Neisseria in the family Neisseriaceae is comprised of 14 genera of Gram-negative diplococci, of which N. gonorrhoeae and N. menigitidis are the two bonafide human pathogens. N. gonorrhoeae (gonococcus) causes gonorrhea, a highly prevalent venereal disease, while N. menigitidis (meningococcus) is the etiologic agent of acute meningitis and fulminant meningococcemia. The only known reservoir for Neisseria species are humans: the upper respiratory tract and genitourinary tract. Rectal carriage of N. gonorrhoeae and N. meningitidis also occurs. Neisseria species are aerobic and facultatively anaerobic and produce oxidase. N. gonorrhoeae is primarily a cause of urethritis in males, and cervicitis and pelvic inflammatory disease in females. In these sites, gonococci adhere to microvilli of columnar epithelium through surface pili, or hair-like filaments extending from the cell surface. Non-piliated organisms are avirulent. Pilin protein structure is antigenically different between strains. Additionally, N. gonorrhoeae can colonize and infect cervical, conjunctival, and rectal mucosa, leading to a purulent inflammatory response. In prepubertal females, N. gonorrhoeae can infect the cuboidal vaginal epithelium, causing vaginitis. Strains with specific types of outer membrane protein II produce opaque colonies, whereas strains lacking these proteins produce transparent colonies. These proteins also enhance gonococcal attachment to buccal epithelial cells and aid intergonococcal adherence, resulting in clumps of organisms termed ‘infectious units’. Outer membrane proteins may also enhance dissemination from colonizing sites, especially in the oral cavity and mediate resistance to serum bactericidal activity. Mucosal pathogens such as N. gonorrhoeae and N. meningitidis also produce
immunoglobulin A protease. N. gonorrhoeae is spread from person to person through contact with infected secretions, usually through the sexual route from asymptomatic or symptomatic individuals. Oral-oral and oral-genital transmission may also occur. Colonization and infection of the oropharynx may lead to dissemination to joints (usually one) rendering septic arthritis, to the pericardium, or aortic valve, causing acute endocarditis, and to the skin, giving petechial lesions, usually on the extremities. Rarely, fulminant gonococcal septicemia with disseminated intravascular coagulation occurs. Conjunctivial epithelium is highly susceptible to gonococcal invasion, rendering a purulent conjunctivitis in newborns (ophthalmia neonatorum) and in other age groups as well.
