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Pathogenesis of gonorrhea in flowchart form (microbiology)

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Pathogenesis of Gonorrhea Flowchart

Pathogenesis of Gonorrhea - Annotated Guide

Here is a step-by-step breakdown of each node, with the textbook mechanisms behind them:

1. Sexual Transmission

N. gonorrhoeae is deposited onto mucosal surfaces - preferentially columnar epithelium of the urethra, endocervix, rectum, pharynx, or conjunctiva. Transmission male→female is ~50-80% per unprotected encounter; female→male is ~20%.

2. Initial Attachment

Three major adhesins work in sequence:
  • Pili (fimbriae) - the primary mediator; piliated strains are far more virulent than non-piliated ones. Pili bind nonciliated columnar epithelial cells.
  • Opa proteins (Protein II) - bind CEACAM receptors, heparan sulfate proteoglycans, and vitronectin on host cells, strengthening adhesion.
  • LOS terminal lactosamine - binds asialoglycoprotein receptors on male epithelial cells, facilitating entry.
Jawetz 28E: "Outer membrane proteins PilC and Opa aid in attachment and local invasion."

3. Invasion & Transcytosis

  • Porin (PorB/Protein I) translocates into the host cell's cytoplasmic membrane, initiating endocytosis.
  • Bacteria are transported through epithelial cells to intercellular spaces near the basement membrane or directly into subepithelial tissue.
  • Opa-CEACAM binding prevents epithelial exfoliation, keeping gonococci anchored.

4. Immune Evasion (Critical Step)

This is where N. gonorrhoeae is especially sophisticated:
MechanismEffect
LOS sialylationInhibits classical + alternative complement pathways; reduces phagocyte binding and PMN oxidative burst
Molecular mimicryLOS mimics human glycosphingolipid structure - evades immune recognition
IgA1 proteaseCleaves and inactivates secretory IgA1 at mucosal surfaces
Antigenic variationPili and Opa proteins undergo rapid phase/antigenic variation - defeats adaptive immunity and vaccine development
Opa-CEACAM1Suppresses CD4+ T lymphocyte activation and proliferation
PorB.1A serum resistanceBinds complement inhibitory molecules - enables bacteremia and DGI

5. Inflammatory Response

  • LOS endotoxin triggers a massive cytokine cascade (IL-1, IL-6, IL-8, TNF-alpha).
  • Intense PMN (neutrophil) infiltration → purulent discharge (classic gonorrheal pus).
  • In the fallopian tube: LOS causes ciliary loss and mucosal cell death directly.

6. Local Complications

Males: Urethra → epididymis → (rarely) prostate/seminal vesicles
Females: Cervix → endometrium → fallopian tubes (salpingitis) → PID → ectopic pregnancy / tubal infertility

7. Disseminated Gonococcal Infection (DGI)

  • Occurs in ~1-3% of cases, almost exclusively PorB.1A strains (serum-resistant, reduced local inflammation → often asymptomatic primary infection).
  • Arthritis-dermatitis syndrome: migratory polyarthralgia, tenosynovitis, pustular/hemorrhagic skin lesions.
  • Can progress to septic arthritis, perihepatitis (Fitz-Hugh-Curtis syndrome), and rarely endocarditis or meningitis.

Virulence Factor Summary Table

FactorRole
PiliAttachment, antigenic variation, genetic competence
Opa (Protein II)Adhesion, invasion, PMN interaction
Porin/PorB (Protein I)Ion channel, endocytosis, serum resistance (1A)
LOSEndotoxin activity, sialylation for immune evasion, molecular mimicry
IgA1 proteaseDestroys mucosal IgA1
Tbp1/Tbp2, LbpA/LbpBIron scavenging from transferrin/lactoferrin in vivo
Rmp (Protein III)Associates with Porin in pore formation
Sources: Harrison's Principles of Internal Medicine 22E (2025), Jawetz Melnick & Adelberg's Medical Microbiology 28E, Sherris & Ryan's Medical Microbiology 8E.
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