Haemophilus ducreyi
Short (1-1.5 × 0.6 Micronmeters)
Ovoid bacelli
Gram negative
Occurs as end-end pairs, short chains
Arrangement: in small groups =》“whorls” or in parallel chains=》“school of fish” / “rail road track” appearance
Primary isolation is difficult
Vancomycin is used as a selective agent for growth on chocolate agar (+ fetal calf serum + isovitalex)
Causes Chanceroid;
aka soft sore
charechterized by tender, nonindurated irregular ulcers on the genitalia.
can spread to regional lymph nodes leading to painful enlargement.