Neisseria gonorrhoeae is a Gram-negative, kidney bean-shaped diplococcus that causes the sexually transmitted infection gonorrhea in humans.
Microbiology and virulence
Neisseria gonorrhoeaebelongs to the family Neisseriaceae and appears as pairs of coffee bean–shaped cells with adjacent flattened sides. It is oxidase-positive, catalase-positive and relies on aerobic respiration but grows best in a moist, 5% carbon dioxide atmosphere on enriched media such as chocolate agar or Thayer-Martin selective medium. Unlike many bacteria, it is extremely sensitive to drying and cold and therefore transmitted almost exclusively by direct contact between mucosal surfaces. The pathogen attaches to columnar epithelial cells in the urogenital tract using fimbrial pili and Opa adhesion proteins. These surface structures undergo phase and antigenic variation, helping the organism evade antibody responses. Its outer membrane contains lipooligosaccharide that triggers inflammation and has sialylation capacity to resist complement. The bacterium produces iron-binding proteins that scavenge iron from host transferrin and secretes proteases that cleave immunoglobulin A. Inside neutrophils it resists killing through antioxidant enzymes and modulates phagosome maturation, enabling survival and spread. The ability to modify its surface and suppress immune responses underpins its persistence and contributes to asymptomatic carriage.
Disease, diagnosis and treatment
Gonorrhea primarily affects mucous membranes of the urethra, cervix, rectum, pharynx or conjunctiva. In men it often presents with urethritis characterized by painful urination and purulent discharge, whereas many infected women have mild or unrecognised cervicitis. Untreated infection can ascend the female reproductive tract, causing pelvic inflammatory disease that may lead to infertility or ectopic pregnancy. Disseminated gonococcal infection occurs when bacteria enter the bloodstream, resulting in arthritis, tenosynovitis and dermatitis. Neonates can develop ophthalmia neonatorum if exposed during delivery. Laboratory diagnosis increasingly relies on nucleic acid amplification tests on urine or swab specimens, which are more sensitive than culture and Gram staining. Culture remains important for antimicrobial susceptibility testing. Current guidelines recommend intramuscular ceftriaxone plus doxycycline or azithromycin to treat coexisting pathogens, but resistance to penicillin, fluoroquinolones and macrolides has emerged worldwide. Vaccines are not yet available, and prevention depends on safe sexual practices, prompt detection and treatment of partners, and surveillance of antimicrobial resistance.
Neisseria gonorrhoeae has evolved numerous strategies to colonise mucosal surfaces and circumvent host defences, leading to a common but often overlooked infection. Understanding its microbiology and monitoring resistance patterns are essential for effective control and treatment.
Related Terms: Gram-negative, Diplococcus, Gonorrhea, Pili, Neisseria meningitidis