What causes gonorrhea?

Updated: Sep 07, 2018
  • Author: Brian Wong, MD; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Answer

N gonorrhoeae is a gram-negative, intracellular, aerobic diplococcus; more specifically, it is a form of diplococcus known as the gonococcus. N gonorrhoeae is spread by sexual contact or through vertical transmission during childbirth. It mainly affects the host’s columnar or cuboidal epithelium. Virtually any mucous membrane can be infected by this microorganism. The physiologic ectopy of the squamocolumnar junction onto the ectocervix in the adolescent female is one factor that causes particular susceptibility to this infection.

Many factors influence the manner in which gonococci mediate their virulence and pathogenicity. Pili help in attachment of gonococci to mucosal surfaces and contribute to resistance by preventing ingestion and destruction by neutrophils. Opacity-associated (Opa) proteins increase adherence between gonococci and phagocytes, promote invasion into host cells, and possibly down-regulate the immune response.

Porin channels (porA, porB) in the outer membrane play key roles in virulence. Gonococcal strains with porA may have inherent resistance to normal human serum and an increased ability to invade epithelial cells, explaining their association with bacteremia.

Certain acquired plasmids and genetic mutations enhance virulence. TEM-1–type beta-lactamase (penicillinase) affects penicillin binding and efflux pumps and confers resistance to penicillin. [11, 12] TetM protects the ribosome and confers resistance to tetracycline. Alterations in gyrA and parC genes result in fluoroquinolone resistance by efflux activation and decreased antibiotic cell permeation. [11]

Gonococci attach to the host mucosal cell (pili and Opa proteins play major roles) and, within 24-48 hours, penetrate through and between cells into the subepithelial space. A typical host response is characterized by invasion with neutrophils, followed by epithelial sloughing, formation of submucosal microabscesses, and purulent discharge. If left untreated, macrophage and lymphocyte infiltration replaces the neutrophils. Some gonococcal strains cause an asymptomatic infection, leading to an asymptomatic carrier state in persons of either sex.

The ability to grow anaerobically allows gonococci, when mixed with refluxed menstrual blood or attached to sperm, to secondarily invade lower genital structures (vagina and cervix) and progress to upper genital organs (endometrium, salpinx, ovaries).

Gonococcal infection usually follows mucosal inoculation during vaginal, anal, or oral sexual contact or perinatally.


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