The Pathogenesis of Disease Due to Nontypeable Haemophilus influenzae

Isolates of Haemophilus influenzae can be separated into encapsulated and nonencapsulated forms. Encapsulated strains express one of six structurally and antigenically distinct capsular polysaccharides, designated serotypes a–f (1 ). In contrast, nonencapsulated strains are defined by their inability to react with antisera against the known H. influenzae polysaccharide capsules and are referred to as nontypeable.