Video - Haemophilus influenzae

Haemophilus influenzae, or just H. influenzae, is a gram-negative, facultatively anaerobic, non-motile coccobacillus. Haemophilus influenzae bacteria are classified into encapsulated strains and unencapsulated strains. Based on their capsular antigen type, encapsulated strains are further classified into six serotypes (serotypes a, b, c, d, e, and f). Unencapsulated strains are also referred to as nontypable because they lack the polysaccharide capsule, and capsular antigens.

Nontypeable strains of Haemophilus influenzae are known to cause relatively simple mucosal infections, like otitis media, sinusitis, and pneumonia. On the other hand, encapsulated strains such as Haemophilus influenza type b can cause more severe infections such as meningitis and epiglottitis, but such severe infections are not so common nowadays due to vaccination.