ABSTRACT
Chancroid is a superficial infection of the external genital tract caused by Haemophilus ducreyi. The bacteria are small gram-negative rods measuring 0.5 mm by 1.5 to 2.0 mm, and are often seen in short chains or parallel arrays (“school-of-fish” or “fingerprint” patterns). They may be cultivated with considerable difficulty, are nonmotile, and are not acid fast. Bipolar staining is often demonstrable.
