A simple medium for the primary isolation of Haemophilus ducreyi

Two simple, inexpensive media containing gonococcal agar-base, supplemented with 5% Fildes' extract and either chocolated or unchocolated horse blood (GC-FHBC or GC-FHB) were compared with the standard gonococcal agar-based (GC-HgS) and Mueller-Hinton agar-based media (MH-HB) normally used for primary isolation of Haemophilus ducreyi from presumptive chancroid lesions. Overall, Haemophilus ducreyi was recovered from 162 of 178 (91%) samples from primary chancroid lesions. As a single isolation medium GC-HgS proved the most sensitive with an isolation rate of 80% followed by GC-FHB (75%), MH-HB and GC-FHC (both 71%). Use of a combination of GC-HgS and MH-HB resulted in isolation of Haemophilus ducreyi in 160 of 178 cases (90%). Since GC-FHB is approximately one-quarter the cost of the combination and half the cost of GC-HgS or MH-HB alone, this medium could prove suitable for diagnostic purposes in developing countries where chancroid is endemic.