Chancroid is a sexually transmitted infection characterized by genital ulcers and tender inguinal lymphadenopathy. Which organism is classically associated with chancroid pathology?

• A. Bordetella pertussis
• B. Bacillus anthracis
• C. Haemophilus ducreyi
• D. Treponema pallidum

Answer: (C)

Chancroid is caused by Haemophilus ducreyi, a Gram-negative coccobacillus that leads to painful genital ulcers with tender inguinal lymphadenopathy. This organism is fastidious and grows best on enriched media (such as chocolate agar with specific supplements), which is a clue that lab confirmation may require special culture conditions or molecular testing. The other organisms listed do not produce this pattern: Bordetella pertussis causes pertussis, Bacillus anthracis causes anthrax, and Treponema pallidum causes syphilis, which typically presents with a painless chancre.