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Chancroid: Diagnosis and Treatment of Soft Chancre

Definition of Chancroid

Chancroid is a sexually transmitted disease caused by Haemophilus ducreyi, leading to genital ulcers (ulcus molle, soft chancre) and painful lymphadenopathy (bubo).

Epidemiology of Chancroid

Mainly in tropical countries, the prevalence has been decreasing for two decades. Only sporadic occurrence in Europe and North America.

Etiology

Pathogen of Chancroid:

Haemophilus ducreyi: immobile gram-negative bacteria, oval cocci arranged in chains.

Signs and Symptoms

Genital Ulcer:

Short incubation period of 3–7 days. Chancroid starts with erythematous papules, which rupture and lead to one or more purulent genital ulcers (ulcus molle). The ulcers are very painful and 2–20 mm in diameter. Genital lymphedema is possible.

Lymphadenopathy

Painful tender groin lumps (bubo) are typical for chancroid in combination with a painful genital ulcer. Untreated chancroid leads to suppurative lymphadenopathy (abscess formation and drainage over the inguinal skin).

Diagnosis of Chancroid

NAAT Swab Test:

Nucleic acid amplification technique (NAAT) has the highest sensitivity for diagnosing H. ducreyi from ulcer exudate.

Culture:

Diagnosis can be achieved with a selective culture, but fast transportation to the lab or bedside inoculation of culture plate is necessary. Culture is particular important in cases of therapeutic failure.

Microscopy:

Microscopic detection of pathogens from the depths of the genital ulcer is possible but with low specificity and sensitivity. The Gram stain shows gram-negative cocci in chain formation [fig. Microscopy: Haemophilus ducreyi].

Microscopy of Haemophilus ducreyi stained using Gentian violet. Fig. from Public Health Image Library, Center for Disease Control and Prevention, USA, https://phil.cdc.gov/.

Further laboratory tests:

Test for syphilis and Herpes simplex for differential diagnosis. Test for HIV and other STDs. Sex partner examination.

Treatment of Chancroid

Recommended antibiotic treatment of Chancroid:

• First choice: azithromycin 1 g p.o. once or ceftriaxone 250 mg i.m. once
• Alternatives: ciprofloxacin 500 mg p.o. 1-0-1 for three days or erythromycin 500 mg p.o. 1-1-1-1 for seven days
• Treat sex partners should be treated even without symptoms or diagnosis.
• Fluctuating lymph nodes and abscess formations: extend antibiotic treatment and needle aspiration or incision and drainage depending on severity.

Resistance to antibiotic treatment is possible. Symptomatic improvement is expected within three days, with objective ulcer healing within seven days of antibiotic therapy.

References

Center for Disease Control and Prevention: “Sexually Transmitted Infections (STI) Treatment Guidelines,” 2021. [Online]. Available: https://www.cdc.gov/std/treatment-guidelines/STI-Guidelines-2021.pdf

IUSTI, “European guideline for the management of chancroid,” 2017. [Online]. Available: https://iusti.org/wp-content/uploads/2019/12/chancroid.pdf.

  Deutsche Version: Ulcus molle (weicher Schanker).