The most common causative organism in epiglottitis is

• A. Parainfluenza
• B. Influenza A
• C. Adenovirus
• D. Hemophilus influenzae

Answer: (D)

Epiglottitis is a sudden, potentially life-threatening swelling of the epiglottis and surrounding tissues, so identifying the typical bacterial cause is key for understanding its presentation and management. Haemophilus influenzae type b is the classic culprit in children; it’s a small encapsulated Gram-negative coccobacillus that can invade the epiglottis and cause rapid, dangerous swelling. Historically, Hib was the most common cause of pediatric epiglottitis, which is why it’s the testable association. The Hib vaccine dramatically reduced these cases, but the organism’s historical prominence makes it the best-known answer for this scenario. It’s also worth noting that Hib requires specific growth factors (X and V) and is cultured on chocolate agar, underscoring its unique microbiology. Other organisms listed are not typical primary causes of epiglottitis in the post-vaccine era, where Hib remains the classic etiologic agent, though non-typeable H. influenzae and other bacteria may appear in vaccinated populations.