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Chapter: Medical Microbiology: An Introduction to Infectious Diseases: Haemophilus and Bordetella

Haemophilus ducreyi

H. ducreyi causes chancroid, a common cause of genital ulcer in Africa, Southeast Asia,India, and Latin America.

Haemophilus ducreyi

H. ducreyi causes chancroid, a common cause of genital ulcer in Africa, Southeast Asia,India, and Latin America. Occasional outbreaks in North America have most often been associated with the exchange of sex for drugs or money. The typical lesion is a tender papule on the genitalia that develops into a painful ulcer with sharp margins. Satellite le-sions may develop by autoinfection, and regional lymphadenitis is common. The incuba-tion period is usually short (2 to 5 days). The lack of induration around the ulcer has caused the primary lesion to be called “soft chancre” to distinguish it from the primary syphilitic chancre, which is typically indurated and painless. The presence of open genital sores due to H. ducreyi enhances the risk of transmission of HIV either by providing a portal of entry or by the recruitment of CD4+ cells to the site. This may contribute to the heterosexual spread of acquired immunodeficiency syndrome (AIDS) on the African con-tinent, where chancroid is common. Candidate H. ducreyi virulence factors include adhe-sive pili, resistance to phagocytosis, and complement-mediated killing. A seeming lack of immunity may be due to the action of a toxin (cytolethal distending toxin) on T cells.

The specific diagnosis of H. ducreyi infection is difficult. Although the organism grows on chocolate agar, it does so slowly and other organisms present in the genital flora are apt to overgrow the plates. A special medium incorporates vancomycin as a selective agent, but few laboratories in the United States have it on hand. Chancroid is effectively treated with azithromycin, ceftriaxone, or erythromycin.


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Medical Microbiology: An Introduction to Infectious Diseases: Haemophilus and Bordetella : Haemophilus ducreyi |


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