Causative Agent of Epiglottitis
Historically, Haemophilus influenzae type b (Hib) was the predominant causative agent of acute epiglottitis, but since widespread Hib vaccination, the epidemiology has shifted dramatically—in children, Hib remains the most common bacterial cause when it occurs, while in adults, Streptococcus pneumoniae and other pathogens have become increasingly important. 1, 2
Historical Context and Vaccination Impact
Before 1985, Hib was the leading cause of bacterial meningitis and invasive diseases including epiglottitis in U.S. children under 5 years. Following introduction of conjugate Hib vaccines (1987-1989), the annual incidence of invasive Hib disease in children decreased by 99% during 1989-2000 1. The overall incidence of acute epiglottitis dropped from 4.5 cases/100,000/year pre-vaccination to 0.98 cases/100,000/year post-vaccination 2.
Current Causative Agents by Age Group
In Children:
- Hib remains the most common bacterial cause when epiglottitis occurs, even in the vaccine era 3, 4
- Recent data from young children (ages 10-15) showed Hib in 34.9% of bacterial isolates from epiglottitis cases 4
- Herpes simplex virus type 1 (HSV-1) was detected in 14.1% of pediatric cases 4
- Other bacterial organisms including Staphylococcus aureus, Streptococcus pyogenes, and Pseudomonas aeruginosa occur less commonly 5, 6
In Adults:
- The causative agent spectrum is broader and more variable 3, 7
- Streptococcus pneumoniae has emerged as the most important bacterial etiology, with incidence increasing from 0.1 to 0.28 cases/100,000/year in adults 2
- Nine of 10 pneumococcal serotypes identified in adult epiglottitis are covered by the 23-valent pneumococcal polysaccharide vaccine (PPV23) 2
- Other causes include viral infections, combined viral-bacterial infections, and noninfectious etiologies 3
- Rare organisms like ampicillin-resistant H. influenzae 8 and Serratia marcescens 9 have been reported
Clinical Implications
Blood cultures are the preferred diagnostic specimen for epiglottitis, as swabbing the epiglottis risks sudden tracheal occlusion from disturbing the swollen tissue 10. If swabbing is attempted, it must be done in a setting with emergency airway management capabilities immediately available.
Key Diagnostic Considerations:
- Direct visualization by laryngoscopy is the gold standard for diagnosis 11
- Lateral neck X-rays have utility but less sensitivity than direct visualization 11
- The disease can progress rapidly to fatal airway obstruction 6, 11
Important Caveats:
- While pediatric mortality has decreased from 7% to about 1% with aggressive treatment, adult mortality remains at approximately 7% 11
- Adults often present with a milder, more variable clinical course than children 11
- All patients require admission to intensive care for close airway monitoring 7
- The shift in epidemiology means clinicians must consider a broader differential of causative organisms, particularly in adults 2, 3