Haemophilus ducreyi, a pleomorphic gram-negative facultative anaerobic bacillus, is the causative agent.
The disease is common in tropical countries.
It is now common in the United States.
Disease is a cofactor for human immunodeficiency virus (HIV) transmission: 10% coinfection rate.
Approximately 10% of patients are coinfected with T. pallidum or herpes simplex virus (HSV).
Sexual contact is the only known method of transmission.
SIGNS AND SYMPTOMS
Incubation period is 2 to 10 days; with a median of 4 to 7 days.
“Soft chancre” is the primary clinical sign.
Shallow, tender, nonindurated ulcer with purulent base
Multiple ulcers in women: lesions on fourchette, labia, vestibule, and clitoris
Unilateral or bilateral inguinal adenopathy (bubo) present in 50% of cases.
Spontaneous rupture if untreated
In HIV patients ulcers are larger, persist longer, and have less extensive lymphadenopathy.
- ducreyi should be isolated from lesion or node aspirate.
Gram stain is insensitive and nonspecific, revealing a pleomorphic gram negative “school of fish” pattern.
Cultures require special media, are 60% to 80% sensitive, and difficult to grow
Rule out HSV, syphilis, and LGV.
Isolation of H. ducreyi is definitive.
Otherwise, clinical diagnosis should include the following:
One or more painful genital ulcers
Negative darkfield examination, negative RPR
Negative HSV, negative LGV
Painful ulcer along with tender inguinal adenopathy is suggestive of chancroid.
Azithromycin, 1 g PO, single dose
Ceftriaxone, 250 mg IM, single dose
Erythromycin base, 500 mg, qid x 7 days
Ciprofloxacin, 500 mg PO, bid x 3 days