Haemophilus ducreyi

Haemophilus ducreyi are fastidious gram-negative coccobacilli bacteria.

This species causes the sexually transmitted disease chancroid, a major cause of genital ulceration in developing countries characterized by painful sores on the genitalia. The first study linking this disease with the agent Hemophilus ducreyi was published in 1889 by Auguste Ducrey. Each year in the United States, there are over 2,000 cases of chancroid. Chancroid starts as an erythematous papular lesion that breaks down into a painful bleeding ulcer with a necrotic base and ragged edge. It has also been found to cause chronic skin ulceration away from the genitalia, infect children and adults, and behave in a manner that mimics yaws.

H. ducreyi can be cultured on chocolate agar and incubated in an environment with elevated humidity and CO₂ enrichment at 33° to 35 °C. It is best treated with a macrolide, e.g. azithromycin, and a third-generation cephalosporin, e.g. ceftriaxone.