A 22-year-old woman presents with multiple small, painful genital ulcers with soft, ragged, undermined edges and a necrotic grey base. Inguinal lymphadenopathy is tender and fluctuant (bubo). Culture on chocolate agar with vancomycin shows gram-negative coccobacilli. What is the causative organism?
- A Treponema pallidum
- B Haemophilus ducreyi ✓
- C Chlamydia trachomatis L1-L3
- D Klebsiella granulomatis
Correct answer: B. Haemophilus ducreyi
Explanation
Chancroid caused by Haemophilus ducreyi is characterized by one or multiple painful, soft genital ulcers with undermined, ragged edges and a purulent base, accompanied by painful inguinal lymphadenopathy that may suppurate to form buboes. The organism is a gram-negative coccobacillus that grows on chocolate agar supplemented with vancomycin. The school-of-fish arrangement of the organism on Gram stain is characteristic. Treatment is with azithromycin or ceftriaxone.
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.