Laboratory diagnosis of Haemophilus ducreyi: sensitivity of culture media.

Laboratory confirmation of the clinical diagnosis of chancroid requires the isolation of Haemophilus ducreyi. Enriched gonococcal (GcHbS) and Mueller-Hinton agar (MHHb) both support the growth of most strains of H. ducreyi. In this study we compared the isolation rate of H. ducreyi on GcHbs and MHHb media in 111 men with genital ulcer disease. A second culture was obtained in 84 men at 48 hr in order to determine the reproducibility of H. ducreyi culture. The sensitivity of a single and a sequential pair of cultures on GcHbS was 67% and 74%, respectively, on men with presumed chancroid. The sensitivity of the MHHb as a single culture was 53%. Using both media for the initial culture of genital ulcers, and repeating the culture on GcHbs at 48 hr, increased the sensitivity of the isolation of H. ducreyi to 92% in men who had no prior antimicrobial use and who had no laboratory evidence of primary syphilis.