Neisseria gonorrhea (STI) symptoms, pathophysiology, complications and treatment

Main ideas, concepts, and lessons

What the organism is

• Neisseria gonorrhoeae is a Gram-negative diplococcus that causes gonorrhea, a sexually transmitted infection (STI).
• It is the second most common bacterial STI worldwide after Chlamydia.
• Untreated infection can lead to serious complications including septic arthritis and pelvic inflammatory disease (PID).
• Increasing incidence is linked to broad-spectrum antibiotic resistance.

Cell structure / key features

• It is an obligate, fastidious Gram-negative bacterium.
• Cell envelope includes:
  • Inner cytoplasmic membrane
  • Middle layer of peptidoglycan
  • Outer membrane
• The outer membrane contains:
  • Lipooligosaccharide (LOS): acts as an endotoxin
  • Phospholipids and various proteins that aid in:
    • Adherence to cells
    • Tissue invasion
    • Resistance to host defenses
• Pili (dynamic polymeric protein filaments) enable:
  • Adherence
  • Movement along surfaces of cells

Transmission routes and risk factors

• Sexual transmission:
  • Oral
  • Genital
  • Anal (rectal)
• Perinatal transmission:
  • Mother to infant during birth
• Risk factors mentioned:
  • Age 20–29
  • Multiple sexual partners
  • Unprotected sex
  • Sex with partners known to have gonorrhea
  • Men who have sex with men
  • Current or prior history of STIs

Pathophysiology (how it causes disease and complications)

• Entry / primary target
  • Mainly infects columnar epithelial cells (e.g., urethral and vaginal epithelium).
• Adherence to host
  • Pili bind to columnar epithelial cells
  • Opa proteins further facilitate adherence
• Virulence factors and immune evasion
  • LOS (endotoxin) causes:
    • Ciliostasis (reduced ciliary function)
    • Sloughing/damage of ciliated epithelial cells
    • Activation of complement and immune cells (macrophages, neutrophils)
    • Resulting acute inflammatory response
  • IgA protease
    • Inactivates host IgA by cleaving it in the hinge region
    • Helps bacteria pass through mucosal areas
  • Capsule
    • Helps evade phagocytosis by macrophages and neutrophils
  • Por proteins
    • Help evade the immune system and support survival/invasion
• Local effects
  • Mucosal invasion → local inflammation → purulent exudate
  • Can spread to other sexual partners
  • LOS is described as attaching to sperm cells, contributing to transmission

Spread (ascending infection) and organ-specific complications

• Ascending urogenital tract can occur.
• In men, infection may cause:
  • Urethritis
  • Epididymitis
  • Prostatitis
• Male symptoms
  • Occur in >90% of infections (as stated)
  • Dysuria
  • Purulent urethral discharge, typically yellow/green
  • Possible abdominal discomfort
• In women, infection may cause:
  • Acute endometritis
  • Salpingitis (inflammation of fallopian tubes)
  • Acute PID
• Female outcomes / long-term complications
  • Infertility
  • Chronic pelvic pain
  • Ectopic pregnancy
• Dissemination and named syndrome
  • Spread to liver capsule via peritoneum → perihepatitis
  • Named Fitz-Hugh-Curtis syndrome
• Female symptoms
  • Occur in only ~50% of cases (as stated), so many are asymptomatic
  • Possible symptoms:
    • Cervicitis (pain/inflammation of cervix)
    • Purulent, yellow, malodorous cervical discharge
    • Dysuria
    • Abdominal/pelvic pain
• Further dissemination
  • Invasion of lymphatics and blood vessels
  • Possible complications listed:
    • Inguinal lymphadenopathy
    • Perineal/perianal and ischiorectal abscesses
    • Periprostatic abscess
    • Endocarditis
    • Disseminated gonococcal infection (DGI) with classic triad:
      • Hemorrhagic vesiculopustular eruption
      • Polyarthralgia
      • Tenosynovitis
• Eye complications
  • Particularly in newborns
  • Can cause permanent blindness if not treated promptly

Diagnosis and differential diagnosis

• Differential diagnosis includes other STIs:
  • Chlamydia trachomatis
  • Trichomonas vaginalis
  • Mycoplasma genitalium
• Investigations / diagnosis:
  • Nucleic acid amplification test (NAAT/NAT)
    • Samples mentioned: urine, urethral discharge, cervical discharge
  • Bacterial culture:
    • From cervix fluid, and from blood if disseminated infection
    • Also from pharynx and joint

Treatment and prevention after treatment

• Treatment
  • Ceftriaxone
  • With possible addition of azithromycin or doxycycline
• Post-treatment sexual avoidance (instructional)
  • No sexual contact for 7 days after treatment
  • No sex with partners from the last 2 months unless those partners have been:
    • tested, and
    • treated if necessary

Overall summary presented

• Neisseria gonorrhoeae is a Gram-negative diplococcus causing gonorrhea.
• Key virulence factors enabling infection/immune evasion include LOS, IgA protease, and a capsule.
• Disease can remain localized in the urogenital tract or disseminate (e.g., to liver or joints), including disseminated gonococcal infection.
• Treatment includes antibiotics such as ceftriaxone (and azithromycin mentioned).
• Prevention includes appropriate partner management and temporary abstinence.

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