15.2 Neisseria gonorrhoeae, Chlamydia trachomatis & Genital Ulcer Diseases

15.2 Neisseria gonorrhoeae, Chlamydia trachomatis & Genital Ulcer Diseases

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Neisseria gonorrhoeae: Pathogenesis, Clinical Spectrum & Resistance

Neisseria gonorrhoeae (the gonococcus) is a fastidious, non-motile, non-spore-forming, aerobic or facultatively anaerobic Gram-negative intracellular diplococcus. Under microscopy, organisms appear kidney bean-shaped with adjacent flattened surfaces, typically residing within polymorphonuclear leukocytes (PMNs). The pathogen selectively infects non-cornified columnar and transitional epithelium of the human urogenital tract, rectum, pharynx, and conjunctiva.

Virulence Factors and Pathogenesis

• Type IV Pili: Mediate initial adherence to mucosal epithelial cells and undergo extensive antigenic variation, frustrating host immune memory.
• Opa (Opacity-Associated) Proteins: Mediate intimate host-cell adhesion, invasion, and inter-bacterial aggregation.
• PorB (Porin B): Facilitates transcellular invasion and inhibits phagolysosomal fusion inside neutrophils.
• Lipooligosaccharide (LOS): Highly endotoxic surface glycolipid lacking repeating O-antigen side chains. Triggers intense activation of Toll-like receptor 4 (TLR4), provoking massive release of tumor necrosis factor-alpha, interleukin-1, and interleukin-8, driving profuse neutrophil recruitment and tissue destruction.
• IgA1 Protease: Cleaves host secretory IgA1 at mucosal surfaces.

Clinical Manifestations

1. Urethritis in Men: Manifests after an incubation period of 2 to 7 days (range 1–14 days). Presents acutely with severe dysuria, burning, and copious, thick, creamy, greenish-yellow purulent urethral discharge. Left untreated, infection can ascend to cause acute epididymo-orchitis, prostatitis, and periurethral abscesses, eventually healing with fibrotic urethral strictures.
2. Cervicitis and Pelvic Inflammatory Disease (PID) in Women: Up to 50% to 70% of endocervical gonococcal infections are entirely asymptomatic, serving as a silent epidemiological reservoir. Symptomatic women present with vaginal discharge, postcoital or intermenstrual bleeding, and dysuria. Physical examination reveals an erythematous, edematous cervix with mucopurulent discharge from the os and contact friability. Ascending infection occurs in 10% to 20% of cases, causing Pelvic Inflammatory Disease (PID) (endometritis, salpingitis, tubo-ovarian abscess). Long-term sequelae include tubal occlusion, chronic pelvic pain, ectopic pregnancy, and tubal factor infertility.
3. Extragenital Gonorrhoea:
   • Pharyngeal Gonorrhoea: Acquired via receptive fellatio. Asymptomatic in over 90% of cases, rarely causing mild exudative pharyngitis. The pharynx represents a crucial anatomical reservoir where high bacterial densities facilitate horizontal genetic exchange and emergence of multidrug-resistant strains.
   • Rectal Gonorrhoea: Acquired via receptive anal intercourse. Often asymptomatic; symptomatic cases present with proctitis (tenesmus, anal pruritus, mucopurulent discharge, and rectal bleeding).
4. Disseminated Gonococcal Infection (DGI): Develops in 0.5% to 3% of untreated mucosal infections due to hematogenous bacteremic spread. Risk factors include terminal complement deficiencies (C5–C9), menstruation, and pregnancy. DGI classically manifests in two distinct phases:
   • The Arthritis-Dermatitis Syndrome: Characterized by fever, chills, migratory asymmetric polyarthralgias, and acute tenosynovitis (classically affecting the extensor tendons of the wrists, fingers, ankles, and toes). Cutaneous lesions are sparse (usually numbering < 30) and located acrally on distal extremities; they begin as erythematous macules that evolve into hemorrhagic, tender pustules or central necrotic bullae on an erythematous base.
   • Septic Monoarthritis: Direct bacterial suppuration of a single large joint (most commonly the knee, wrist, or ankle). The joint is hot, tensely swollen, and exquisitely painful, with purulent synovial fluid exhibiting high leukocytosis (> 50,000 WBC/µL).

European IUSTI Diagnostic and Treatment Guidelines

• Diagnostic Standards:
  • Nucleic Acid Amplification Testing (NAAT): The gold standard for screening and diagnosis due to exceptional sensitivity (>95%) and specificity (>99%). Recommended specimens: First-void urine (FVU) in men; self-collected or clinician-collected vulvovaginal swabs in women; and targeted rectal and pharyngeal swabs in individuals practicing receptive anal or oral sex.
  • Gram Stain Microscopy: Highly sensitive (>95%) and specific in symptomatic male urethritis, visualizing Gram-negative intracellular diplococci within PMNs. Unreliable for cervical, pharyngeal, or rectal specimens.
  • Bacterial Culture: Mandatory for all NAAT-positive specimens or clinical treatment failures. Culture on selective enriched media (e.g., modified Thayer-Martin, New York City medium) is the only method that permits Antimicrobial Susceptibility Testing (AST).
• Treatment Regimens (European IUSTI Standards):
  • Uncomplicated Urethral, Cervical & Rectal Infection (susceptibility unknown): Ceftriaxone 1 g IM PLUS Azithromycin 2 g orally, both as single doses.
  • Ceftriaxone 1 g IM Monotherapy: Only where quality-assured local surveillance shows no ceftriaxone resistance, a test of cure is mandatory, the patient is very likely to return, and doxycycline 100 mg twice daily for 7 days is added if C. trachomatis has not been excluded by NAAT.
  • Severe β-Lactam Allergy: Spectinomycin 2 g IM PLUS Azithromycin 2 g orally, or Gentamicin 240 mg IM PLUS Azithromycin 2 g orally (spectinomycin is not reliable for pharyngeal infection).
  • Disseminated Gonococcal Infection (DGI): Hospital admission; ceftriaxone 1 g IM or IV every 24 hours (alternatives cefotaxime or spectinomycin), continued for 7 days in total, with a switch to oral therapy guided by susceptibility testing 24–48 hours after substantial improvement.
  • Test of Cure (TOC): Recommended in all cases to detect treatment failure and emerging resistance: culture 3–7 days after treatment when symptoms persist, or NAAT 2 weeks after treatment in asymptomatic patients.
  • Sexual Contacts: All contacts within the preceding 3 months should be tested and treated if positive (or treated epidemiologically if they may not return).

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Chlamydia trachomatis: Biology, Serovars & Syndromes

Chlamydia trachomatis is an obligate intracellular bacterium with a unique biphasic developmental cycle characterized by two functional morphological forms:

• Elementary Body (EB): Small (0.3 µm), metabolically inactive, infectious extracellular form. Possesses a rigid, highly cross-linked disulfide outer membrane that resists harsh environmental stress. The EB attaches to and enters host columnar epithelial cells via endocytosis.
• Reticulate Body (RB): Larger (1.0 µm), metabolically active, replicating intracellular form. Inside the host cytoplasmic endosome (chlamydial inclusion), the EB differentiates into an RB, synthesizes bacterial proteins, and divides by binary fission before condensing back into EBs to lyse the host cell.

Serovar Classification and Pathological Spectra

Clinical Syndromes (Serovars D–K)

• Non-Gonococcal Urethritis (NGU): Incubation of 1 to 3 weeks. Compared to gonorrhoea, symptoms are milder: mild to moderate dysuria and scant, watery, clear or mucoid urethral discharge, often most pronounced in the morning.
• Cervicitis and Pelvic Inflammatory Disease: Asymptomatic in 70% to 80% of women. Symptomatic cervicitis presents with hypertrophic ectopy, cervical edema, and mucopurulent discharge. Ascending salpingitis leads to chronic pelvic pain, ectopic pregnancy, and tubal infertility.
• Fitz-Hugh-Curtis Syndrome (Perihepatitis): Complication occurring in 10% to 15% of women with chlamydial (or gonococcal) PID. Manifests as sharp, pleuritic right upper quadrant (RUQ) abdominal pain radiating to the right shoulder. Liver enzymes are typically normal or only mildly elevated. Direct laparoscopy demonstrates pathognomonic "violin-string" fibrous peritoneal adhesions between the liver capsule and the anterior peritoneal wall.
• Reactive Arthritis: Triad of urethritis, migratory polyarthritis, and conjunctivitis/uveitis occurring 1 to 4 weeks after chlamydial infection, associated with HLA-B27. Cutaneous findings include keratoderma blennorrhagica (hyperkeratotic pustular and crusting lesions on palms and soles) and circinate balanitis (painless erosive serpiginous plaques on the glans penis).
• Neonatal Transmission: Transmitted during passage through an infected birth canal:
  • Ophthalmia Neonatorum: Acute conjunctivitis presenting 5 to 14 days after birth with copious purulent discharge.
  • Infant Interstitial Pneumonia: Develops at 1 to 3 months of age, presenting with a distinctive afebrile "staccato cough", tachypnea, and diffuse bilateral interstitial infiltrates.

Lymphogranuloma Venereum (LGV: Serovars L1–L3)

LGV is an invasive, lymphotropic systemic infection that has resurged significantly across Europe, particularly among men who have sex with men (MSM):

• Primary Stage: Transient, painless small papule, shallow vesicle, or erosion at the site of inoculation (genitalia or rectum). Heals rapidly within a few days without leaving a scar and is frequently overlooked.
• Secondary Stage (Inguinal Syndrome): Occurs 2 to 6 weeks later. Characterized by painful, firm, unilateral (less commonly bilateral) inguinal and femoral lymphadenopathy (buboes). When lymph nodes both above and below the inguinal ligament (Poupart's ligament) enlarge simultaneously, they produce the classic "groove sign" of Greenblatt. Buboes become fluctuant, adhere to overlying violaceous skin, and rupture through multiple draining sinus tracts discharging thick pus.
• Anorectal Syndrome (Proctitis): The predominant modern clinical presentation among MSM. Manifests as severe, ulcerative, hemorrhagic proctitis / proctocolitis characterized by severe rectal pain, tenesmus, bloody purulent rectal discharge, and constipation, clinically and histologically mimicking Crohn's disease or ulcerative colitis.
• Tertiary Stage: Untreated chronic lymphatic obstruction causes severe fibrotic destruction, chronic fistulae, rectal strictures, and genital elephantiasis (esthiomène).

Treatment Protocols (European IUSTI)

• Uncomplicated Urogenital Chlamydia (Serovars D–K):
  • First-Line: Doxycycline 100 mg orally twice daily for 7 days. (European guidance prefers doxycycline to single-dose azithromycin because randomised evidence shows higher microbiological cure, especially for rectal infection).
  • Alternative / Pregnancy: Azithromycin 1.0 g orally single dose, or Amoxicillin 500 mg orally three times daily for 7 days (doxycycline is strictly contraindicated in pregnancy).
• Lymphogranuloma Venereum (LGV):
  • First-Line: Doxycycline 100 mg orally twice daily for 21 days (a 3-week course is standard for LGV).
  • Alternative: Erythromycin 500 mg orally four times daily for 21 days.

Differential Diagnosis of Genital Ulcer Diseases (GUD)

Genital ulcer disease encompasses a critical clinical spectrum in venereology. Accurate syndromic and microbiological differentiation is essential for rapid therapeutic intervention and prevention of HIV transmission.

1. Chancroid (Soft Chancre / Ulcus Molle)

• Etiology: Haemophilus ducreyi, a fastidious Gram-negative facultative anaerobic coccobacillus.
• Incubation: Short, typically 3 to 7 days.
• Ulcer Morphology: Begins as an inflammatory macule or tender pustule that rapidly ruptures into an exquisitely painful, soft (non-indurated) ulcer. The ulcer exhibits ragged, sharply demarcated, undermined edges, a dirty yellow-gray purulent base, and easily bleeds when touched. Lesions are frequently multiple due to autoinoculation ("kissing ulcers").
• Lymphadenopathy: In 50% of patients, painful, tender, unilateral acute inguinal lymphadenitis (suppurative bubo) develops 1 to 2 weeks after ulcer onset. Buboes become fluctuant, adhere to overlying red skin, and can spontaneously rupture through a single sinus tract.
• Microbiology: Direct smear microscopy stained with Gram or Giemsa shows Gram-negative coccobacilli arranged in parallel chains or clusters reminiscent of a "school of fish" or "railroad tracks". Culture requires specialized enriched gonococcal agar; NAAT/multiplex PCR is diagnostic.
• European First-Line Treatment: Azithromycin 1.0 g orally single dose OR Ceftriaxone 250 mg (or 500 mg) IM single dose.

2. Donovaniasis (Granuloma Inguinale)

• Etiology: Klebsiella granulomatis (formerly Calymmatobacterium granulomatis), a pleomorphic, encapsulated Gram-negative intracellular bacterium.
• Incubation: Prolonged and variable, ranging from 1 to 12 weeks (up to 6 months).
• Ulcer Morphology: Begins as a painless subcutaneous papule or nodule that ulcerates into an expansive, painless, exuberant, beefy-red vascular ulcer with rolled, elevated borders. The base consists of clean, velvety, highly vascular granulation tissue that bleeds profusely upon light touch. Mutilating tissue destruction and cicatricial scarring occur over time.
• Lymphadenopathy: True lymphadenopathy is absent! Instead, patients develop "pseudobuboes", which are subcutaneous perilymphatic granulomatous nodules in the inguinal folds that fluctuate and ulcerate, mimicking lymphadenitis.
• Microbiology: Cannot be cultivated on artificial media. Diagnosis requires examination of crushed tissue preparations or punch biopsy stained with Wright-Giemsa or Leishman stain, visualizing large mononuclear cells (macrophages) containing numerous pleomorphic encapsulated bacilli with bipolar condensation resembling closed "safety pins" (Donovan bodies).
• European First-Line Treatment: Azithromycin 1.0 g orally once weekly or 500 mg daily until complete epithelialization and clinical healing of all lesions has occurred (minimum duration: 3 weeks).

3. Genital Herpes Simplex (HSV)

• Etiology: Herpes Simplex Virus Type 2 (HSV-2 in ~70–80% of recurrent genital disease) and Type 1 (HSV-1, increasingly common in young adults due to oral-genital sex).
• Incubation: 2 to 12 days (average 4 days).
• Clinical Presentation: Primary episode presents with systemic prodromal fever, headache, and severe local burning, followed by the eruption of multiple grouped vesicles on an erythematous base. The vesicles rupture within 24 to 48 hours to form extremely painful, shallow, punched-out polycyclic erosions with scalloped erythematous margins. Lesions heal without scarring in 2 to 3 weeks. Recurrent episodes are milder, localized, and heal in 5 to 10 days.
• Lymphadenopathy: Tender, firm, bilateral, non-suppurative inguinal lymphadenopathy.
• Microbiology: Real-time multiplex viral PCR is the gold standard for detection and typing. Tzanck smear demonstrates multinucleated acantholytic giant cells with ballooning degeneration and Cowdry A inclusion bodies.
• European First-Line Treatment: Primary episode: Valaciclovir 500 mg orally twice daily for 5 to 10 days (or Aciclovir 400 mg orally three times daily for 5–10 days). Suppressive therapy for frequent recurrences (≥ 6 episodes/year): Valaciclovir 500 mg orally once daily.

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Master Genital Ulcer Disease Comparison Table