Chancroid (soft chancre) is the most common of the minor venereal diseases. It is caused by the short gram-negative rod H. ducreyi. The male/female ratio of reported cases is approximately 10:1. Chancroid predominantly affects heterosexual men, and most cases originate from prostitutes who are often carriers with no symptoms. The disease is common and endemic in many parts of the world. In the United States chancroid typically occurs in epidemics. A high rate of HIV infection among patients with chancroid has been reported.
After an incubation period of 3 to 5 days, a painful, red papule appears at the site of contact and rapidly becomes pustular and ruptures to form an irregular-shaped, ragged ulcer with a red halo. The ulcer is deep, not shallow as in herpes; bleeds easily; and spreads laterally, burrowing under the skin and giving the lesion an undermined edge and a base covered by yellow-gray exudate. The ulcers are highly infectious, and multiple lesions appear on the genitals from autoinoculation. Unlike syphilis, the ulcers may be so painful that some patients refuse the manipulation necessary to obtain culture material. Untreated cases may resolve spontaneously or, more often, progress to cause deep ulceration, severe phimosis, and scarring. Systemic symptoms, including anorexia, malaise, and low-grade fever, are occasionally present. Females may have multiple, painful ulcers on the labia and fourchette and, less often, on the vaginal walls and cervix. Autoinoculation results in lesions on the thighs, buttocks, and anal areas. Female carriers may have no detectable lesions and may be without symptoms.
Unilateral or bilateral inguinal lymphadenopathy develops in approximately 50% of untreated patients, beginning approximately 1 week after the onset of the initial lesion. The nodes then resolve spontaneously or they suppurate and break down.
The combination of a painful ulcer with tender inguinal adenopathy is suggestive of chancroid and, when accompanied by suppurative inguinal adenopathy, is almost pathognomonic.
Accurate diagnosis depends on the ability to culture H. ducreyi. Amies transport medium and all the newly formulated transport media maintain viability of H. ducreyi for more than 4 days at 4° C.
H. ducreyi possesses agglutination properties that account for the clumping of organisms when colonies are dispersed in saline. Agglutination may be responsible for the "school-of-fish" pattern seen on Gram staining. Gram-negative coccobacilli occur in parallel arrays (school-of-fish arrangement). This feature is infrequently seen and other gram-negative bacilli in the smear may result in a false-positive diagnosis. Bacteria may be intracellular.
Herpes simplex genital ulcers can mimic chancroid. A herpes culture and Tzanck smear to look for virus-induced, multinucleated giant cells help to establish the diagnosis. The histologic nature of chancroid is specific, but the biopsy procedure is so painful that other means of confirming the diagnosis should be utilized first.