Neisseria gonorrhoeae

Snapshot

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  • 19-year-old male college student presents to the clinic complaining of a burning sensation with urination as well as purulent urethral discharge. He admits to rarely using condoms during sexual intercourse, and does not recall the last time he was tested for sexually-transmitted infections. Urinalysis is positive for leukocyte esterase and a Gram stain shows intracellular diplococci within polymorphonuclear neutrophils.

Introduction

  • Classification
    • Neisseria
      • Gram-negative diplococci
      • often intracellular within neutrophils
  • Epidemiology
    • incidence
      • the second most common bacterial sexually-transmitted infection (after Chlamydia)
    • location
      • genital tract
    • risk factors
      • unprotected sexual intercourse 
  • Pathogenesis
    • mechanism
      • molecular biology
        • pili facilitate attachment to mucosal surfaces
        • antigenic variation  
        • IgA protease allows invasion of mucosal surfaces
        • contains lipooligosaccharides (LOS) with strong endotoxin activity
      • invasion of mucosal surfaces results in inflammation
    • transmission
      • sexual
      • perinatal
  • Associated conditions
    • septic arthritis 
    • neonatal conjunctivitis (2-5 days after birth) https://step1.medbullets.com/images/question_step_1.png
      • prophylaxis with erythromycin eye drops
    • pelvic inflammatory disease (PID)
  • Fitz-Hugh-Curtis syndrome

Presentation

  • Symptoms
    • dysuria
    • purulent discharge
    • fever
    • prostatitis (men)
    • endocervicitis (women)
  • urethritis

Studies

  • Labs
    • Cervical and urethral culture
      • Thayer-Martin agar
        • selects for growth of Neisseria
        • contains vancomycin, trimethoprim, colistin, and nystatin to inhibit growth of Gram-positive organisms, Gram-negative organisms except for Neisseria, and fungi
    • Nucleic acid amplification testing (NAAT)
  • Histology
    • Gram stain of a cervical swab
  • Gram-negative kidney-shaped diplococci 

Differential

  • Chlamydia
    • distinguishing factor
      • visualization of intracytoplasmic inclusions (reticulate bodies) on histology
  • Urinary tract infection
    • distinguishing factor
      • lack of growth on Thayer-Martin agar
  • Genital herpes simplex
    • distinguishing factor
  • painful vesicles and ulcers

Treatment

  • Medical
    • IM ceftriaxone
  • add azithromycin or doxycycline for possible concomitant chlamydial infection

Complications

  • Pelvic inflammatory disease (PID)
    • may include salpingitis, endometritis, hydrosalpinx, tubo-ovarian abscess
    • risk factor for ectopic pregnancy, infertility, chronic pelvic pain, and adhesions
  • Fitz-Hugh-Curtis Syndrome
    • perihepatitis
      • infection and inflammation of liver capsule
      • adhesions of peritoneum to liver

Comparison with N. meningitidis

CharacteristicsN. gonorrhoeaeN. meningitidis
AppearanceKidney-bean shaped diplococci
Oxidase testPositive
Polysaccharide capsuleNoYes
FermentationGlucose (“Gonococci”)Maltose and Glucose (“MeninGococci”)
TransmissionSexRespiratory
VaccineNo (due to rapid antigenic variation)Yes
β-lactamase productionCommonRare
IgA protease productionYes