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Chancroid is infection of the genital skin or mucous membranes caused by Haemophilus ducreyi and characterized by papules, painful ulcers, and enlargement of the inguinal lymph nodes leading to suppuration. Diagnosis is usually clinical because culturing the organism is difficult. Treatment is with a macrolide (azithromycin or erythromycin), ceftriaxone, or ciprofloxacin.
H. ducreyi is a short, slender, gram-negative bacillus with rounded ends. Chancroid occurs in rare outbreaks in developed countries but is a common cause of genital ulcers throughout much of the developing world and often acquired by men from prostitutes. Like other sexually transmitted diseases (STDs) causing genital ulcers, chancroid increases risk of HIV transmission. In the US, about 10% of patients with chancroid are also infected with Treponema pallidum or herpes simplex virus.
After an incubation period of 3 to 7 days, small, painful papules appear and rapidly break down into shallow, soft, painful ulcers with ragged, undermined edges (ie, with overhanging tissue) and a red border. Ulcers vary in size and often coalesce. Deeper erosion occasionally leads to marked tissue destruction. The inguinal lymph nodes become tender, enlarged, and matted together, forming a pus-filled abscess (bubo). The skin over the abscess may become red and shiny and may break down to form a sinus. The infection may spread to other areas of skin, resulting in new lesions. Phimosis, urethral stricture, and urethral fistula may result from chancroid.
Chancroid is suspected in patients who have unexplained genital ulcers or buboes (which may be mistaken for abscesses) and who have been in endemic areas. Genital ulcers with other causes (see Table: Differentiating Common Sexually Transmitted Genital Lesions) may resemble chancroid.
If available, a sample of pus from a bubo or exudate from the edge of an ulcer should be sent to a laboratory that can identify H. ducreyi. However, diagnosis is usually based on clinical findings alone because culture of the bacteria is difficult and microscopic identification is confounded by the mixed flora in ulcers. PCR testing is not commercially available, but several institutions have certified tests that are highly sensitive (98.4%) and specific (99.6%) for H. ducreyi. Clinical diagnosis has a lower sensitivity (53 to 95%) and specificity (41 to 75%).
Serologic testing for syphilis and HIV and cultures for herpes should be done to exclude other causes of genital ulcers. However, interpretation of test results is complicated by the fact that genital ulcers due to other conditions may be coinfected with H. ducreyi.
Treatment should be started promptly, without waiting for test results. One of the following is recommended:
Patients treated for other causes of genital ulcers should be given antibiotics that also treat chancroid if chancroid is suspected and laboratory testing is impractical. Treatment of patients with HIV coinfection, particularly with single-dose regimens, may be ineffective. In these patients, ulcers may require up to 2 wk to heal, and lymphadenopathy may resolve more slowly.
Buboes can safely be aspirated for diagnosis or incised for symptomatic relief if patients are also given effective antibiotics.
Sex partners should be examined, and patients should have a serologic test for syphilis and HIV in 3 mo.
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