Haemophilus ducreyi.

Haemophilus ducreyi is the etiologic agent of chancroid, an infection which is endemic in tropical and subtropical areas of the world and which is becoming more prevalent in Europe and North America. Recently, several strains have demonstrated resistance to several antimicrobials by plasmid acquisition and cell envelope alteration making control of the spread of this organism a challenge. Equally challenging is the growth of this organism in the clinical microbiology laboratory because of its in vitro fastidious nature. Currently, the therapy of choice for Haemophilus ducreyi infection is trimethoprim sulfamethoxazole or erythromycin. Plasmid enumeration and restriction endonuclease fingerprinting in addition to outer membrane protein profiles may provide a basis for subtyping which would be useful in epidemiologic studies.