Haemophilus ducreyi is the causative agent of which disease?

• A. Chancroid
• B. Lymphogranuloma venereum
• C. Trachoma
• D. Whooping cough

Answer: (A)

Haemophilus ducreyi causes chancroid, an sexually transmitted infection that presents with a painful genital ulcer and tender inguinal lymphadenopathy. This organism is a fastidious Gram-negative coccobacillus, and diagnosis is typically supported by culture on enriched media or by PCR when culture is difficult. Clinically, chancroid ulcers have ragged, undermined edges and a base that may exude purulent material, with inguinal lymph node swelling that can form buboes. This helps differentiate it from other conditions listed: lymphogranuloma venereum is caused by Chlamydia trachomatis L1–L3 and often begins with a small, sometimes unnoticed lesion followed by painful buboes; trachoma is an ocular infection caused by Chlamydia trachomatis; whooping cough is a respiratory disease caused by Bordetella pertussis. Treatment typically includes antibiotics such as azithromycin or ceftriaxone.