Haemophilus influenzae

Bacterial Information	Value
Taxonomy level	Species
NCBI Taxonomy ID	727
Phylum	Proteobacteria
Family	Pasteurellaceae
Genus	Haemophilus
Gram stain	Gram-negative
Oxygen requirements	Facultatively-anaerobic
Spore-forming	No
Motile	No
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Table of Contents

• Haemophilus influenzae
  • Table of Contents
  • Overview
  • Biological information
    • Detection

Overview

Haemophilus influenzae is a gram-negative, facultatively anaerobic bacterium that is a frequent inhabitant of the human upper respiratory tract. H. influenzae has been classified into six different serotypes (a-f) based on the capsular antigens expressed on the cell surface. Of these, type b (Hib) has been associated with severe invasive infections such as meningitis, pneumonia, and bacteremia, particularly in young children. Non-typeable H. influenzae (NTHi) lacks the capsular antigen and is a common cause of otitis media, sinusitis, and other respiratory infections.

Biological information

Detection

Haemophilus influenzae can be detected in a variety of biological niches, primarily in the human upper respiratory tract. It is a normal commensal of the nasopharynx in many individuals and can be found in the tonsils, adenoids, sinuses, and middle ear of some individuals. H. influenzae can also colonize the lower respiratory tract, particularly in patients with chronic obstructive pulmonary disease (COPD) or cystic fibrosis.

In addition to its presence in human respiratory tissues, it has been detected in other biological niches such as the genital tract and the conjunctiva. It has also been isolated from blood and cerebrospinal fluid in cases of invasive disease such as meningitis and bacteraemia.