Cultural diagnosis of chancroid.

Culture of Haemophilus ducreyi remains the definitive way to diagnose chancroid. Since its discovery in 1889, cultural isolation of this fastidious organism has been a challenge for clinicians and microbiologists. A recent chancroid epidemic in our locale prompted a review of available culture techniques. Despite the development of various selective solid media in the last 20 years, cultural diagnosis of chancroid remains problematic. Many pitfalls may complicate this procedure, such as concomitant syphilis, syphilis, or herpes progenitalis simulating chancroid, strain differences in nutritional requirements, improper handling and delayed inoculation of clinical specimens, use of suboptimal growth conditions, and vancomycin hydrochloride-sensitive organisms. Highest cultural yield will be obtained by using enriched gonococcal agar base and enriched Müeller-Hinton agar in a biplate fashion. As most isolates are sensitive to vancomycin, incorporation of this antibiotic should be routine. However, screening for vancomycin-sensitive organisms is indicated when negative cultures are repeatedly obtained from clinically typical cases originating from the same community. Development of immunodiagnostic and DNA probe tests is underway.