For Clinicians
Etiologic agent
Haemophilus influenzae is a pleomorphic gram-negative coccobacillus. H. influenzae may be either encapsulated (typeable) or unencapsulated (nontypeable). There are 6 encapsulated serotypes (designated a through f) that have distinct capsular polysaccharides.
Clinical features
Disease caused by H. influenzae can affect many organ systems. The most common types of disease caused by H. influenzae type b (Hib) include
- Pneumonia
- Bacteremia
- Meningitis
- Epiglottitis
- Septic arthritis
- Cellulitis
- Otitis media
- Purulent pericarditis
Less common infections include endocarditis and osteomyelitis.
Non-b but typeable (i.e., a, c, d, e, and f) H. influenzae (hereto after referred to as non-b H. influenzae) can cause disease similar to Hib infections. Nontypeable H. influenzae commonly causes ear infections in children and bronchitis in adults, but can also cause invasive disease.
Entire content available on: https://www.cdc.gov/hi-disease/clinicians.html
