Chancroid

Chancroid is a highly transmissible STD caused by Haemophilus ducreyi. The disease presents with painful ulcer(s) on the genital tract (termed chancroid or “soft chancre”). Up to 50% of patients will develop painful inguinal lymphadenopathy. Furthermore, of that percentage, 25% may develop complications of the suppurative lymph nodes. Given the growth of H. ducreyi on a special medium (often not readily available), chancroid is diagnosed based upon clinical appearance and tests to rule out both syphilis and herpes (the most common causes of genital ulcers). Although the disease can resolve spontaneously, antibiotics (azithromycin or ceftriaxone) are the treatment of choice. Treatment should involve both patients and their sexual contacts.

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Overview

Definition

Chancroid (soft chancre) is a sexually transmitted disease caused by a bacterium, Haemophilus ducreyi, characterized by painful genital ulcer and suppurative inguinal adenopathy.

Etiology

  • H. ducreyi:
    • Gram negative
    • Nonspore forming
    • Nonmotile
    • Facultative anaerobic coccobacillus
    • Grows best in a humid atmosphere
  • Associated risk factors for STD:
    • Uncircumcised men
    • Low socioeconomic status
    • Poor hygiene
    • Risky sexual behavior (drug abuse, prostitution)

Epidemiology

  • Chancroid is an uncommon infection in most developed countries.
    • In 2011, < 20 cases were recorded in the United States.
    • In 2016, 7 cases were recorded in the United States.
  • Common in the following regions: 
    • Sub-Saharan Africa
    • Southeast Asia
    • Latin America

Pathophysiology

  • H. ducreyi infection dependent upon:
    • Size of inoculum (100 colony-forming units carry a 90% risk of infection)
    • Host factors
  • Transmission: H. ducreyi enters via skin microabrasions and causes mucosal breaks during sexual contact.
  • Infection process: Pathogen produces a cytolethal distending toxin → irreversible epithelial damage and death → ulceration

Clinical Presentation

  • Incubation period: Patients usually develop a lesion between 4 and 10 days postexposure.
  • Lesion:
    • Erythematous papule develops at the site of inoculation.
    • Papule → pustule → ulcer(s)
    • Chancroid:
      • 1–2 cm (0.39–0.79 in)
      • Painful
      • Erythematous base
      • Well-demarcated borders and ragged edges
      • Gray or yellow purulent exudate
  • Affects genital areas and draining lymph nodes:
    • In men:
      • Corona, prepuce, or glans of the penis
    • In women: 
      • Labia, introitus, and perianal areas
      • Can be asymptomatic, if vaginal and cervical areas are affected
    • Lymphadenopathy:
      • 50% will develop tender, unilateral inguinal lymphadenopathy.
      • 25% will develop buboes with subsequent ulceration within 2 weeks.

Diagnosis

Diagnosis is made by clinical judgment and tests to rule out the 2 most common causes of genital ulcers, herpes simplex virus (HSV) and syphilis.

  • Confirmed diagnosis is made by isolation of H. ducreyi on culture (the special media is not widely available).
  • Gram stain: Organisms appear as parallel strands resembling a “railroad track” or a “school of fish.”
  • Nucleic acid amplification tests are not readily available outside of clinical research.
  • Probable diagnosis:
    • ≥ 1 painful ulcer(s) are present.
    • Symptoms and signs match that of a typical chancroid lesion.
    • Negative PCR test for HSV
    • No evidence of Treponema pallidum (darkfield microscopy or serologic testing)

Haemophilus ducreyi bacteria

Image: “Haemophilus ducreyi 01” by CDC. License: Public Domain

Management

General principles

  • Disease course and treatment:
    • Lesion(s) can spontaneously resolve within 3 months but can be complicated by lymphadenitis and suppurative buboes.
    • Antimicrobial therapy is the mainstay of treatment to avoid the formation of buboes.
  • Additional recommendations:
    • Patients must be screened for other STDs.
    • Unprotected sexual intercourse should be avoided during treatment (until the ulcers have resolved).
    • Sexual partners should also be treated regardless of the symptoms.

Medical management

  • 1st-line treatment: Azithromycin 1 g orally (by mouth) as a single dose or ceftriaxone 250 mg given IM as a single dose:
    • Advantage of increased compliance, as they are administered as a single-dose regimen.
    • Safe for pregnant women
  • Alternatives:
    • Ciprofloxacin (3-day course)
    • Erythromycin (7-day course)
  • Empiric treatment for HSV and syphilis is also recommended (as they are more common and coinfections may exist).

Surgical management

  • Incision and drainage of suppurative buboes
  • Needle aspiration can be performed, but patients may need repeat aspirations.
  • Without treatment, fistulous tracts and deep tissue destruction can occur.

Differential Diagnosis

  • Herpes simplex: common STD caused by HSV type 1 or 2. Prodromal symptoms often precede clusters of painful and fluid-filled vesicles on an erythematous base. These vesicles eventually form ulcers, which can coalesce. Lymphadenopathy, dysuria, and severe neuralgia can occur. The diagnosis is generally clinical but confirmed with PCR and serologic testing. Management includes antiviral therapy.
  • Syphilis: this STD is caused by T. pallidum and has 4 clinical stages. Primary syphilis begins with a solitary painless ulcer on the genitals (chancre). Progression to secondary syphilis manifests as a generalized maculopapular rash, which includes the palms and soles. The development of tertiary syphilis can cause severe neurologic (neurosyphilis), cardiovascular, and/or gummatous disease. The dormant period between secondary and tertiary syphilis is the latent stage.
  • Donovanosis: rare STD caused by Klebsiella granulomatis. The progressive, nodular genital lesions can form into painless ulcerations, which cause tissue damage. Lymphadenopathy is not common. The diagnosis is with microscopic findings of Donovan bodies from the lesion. Management involves antibiotics, such as macrolides, tetracyclines, and trimethoprim-sulfamethoxazole.
  • Lymphogranuloma venereum: STD caused by 3 strains of Chlamydia trachomatis. Patients may have a small, self-limited genital ulcer, followed by painful inguinal and/or femoral lymphadenopathy. Diagnosis is clinical. Although PCR testing can help with diagnosis, the availability of this testing is limited. Management involves tetracyclines or erythromycin.

References

  1. Hicks, C. B. (2019). Chancroid. UpToDate. Retrieved March 01, 2021, from https://www.uptodate.com/contents/chancroid
  2. Irizarry, L., Velasquez, J., & Wray, A. A. (2020). Chancroid. StatPearls. Retrieved March 01, 2021, from https://www.ncbi.nlm.nih.gov/books/NBK513331/
  3. Riedel, S., Morse, S. A., Mietzner, T. A., & Miller, S. (2019). Haemophilus, bordetella, brucella, and francisella. Jawetz, Melnick, & Adelberg’s Medical Microbiology, 28e. McGraw-Hill.

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