Presumptive microscopic identification of Haemophilus ducreyi can be made from clinical material obtained from a lesion. By employing 10 ml of patient's blood (inactivated at 56 C for 30 minutes) as a cultural medium and serous fluid from the lesion as an inoculum, confirmation may be completed within 48 hours. A total of 24 patients with presumptive diagnosis of chancroid were examined and 21 of these showed H ducreyi on smears and culture.
Borchardt KA, Hoke AW. Simplified Laboratory Technique for Diagnosis of Chancroid. Arch Dermatol. 1970;102(2):188-192. doi:10.1001/archderm.1970.04000080060011