Chancroid is one of the genital ulcer diseases (GUD). The diagnosis can be a challenge, especially where resources are limited.
Cause: Haemophilus ducreyi
PCR, DNA probes or other molecular method has become a preferred method.
A Gram stain is relatively insensitive and nonspecific, showing a Gram-negative coccobacillus. The use of immunofluorescence with specific antibodies improves sensitivity and specificity, and can help confirm the culture isolate.
Transport media: Stuart's, Amies's, or thioglycolate hemin, held at 4°C for up to 4 days. Cold storage may improve recovery.
Culture can be difficult since the organism is fastidious and requires:
(1) media (GC agar, Mueller Hinton, other) with supplements (hemoglobin/heme source, IsoVitaleX, activated charcoal, selenium dioxide, albumin). Some isolates may grow on one media and not another, so use of several types of media is more sensitive but can be expensive.
(2) addition of vancomycin to suppress Gram-positive bacteria (3 mg/L)
(3) incubation temperature: 33 to 35°C
(4) atmosphere: microaerophilic, high humidity, 5% carbon dioxide and with hydrogen
(5) duration: Growth may be slow so the plates should be held beyond 2 days.
