H. aegyptius H. ducreyi H. felis H. haemoglobinophilus[1] H. haemolyticus H. influenzae H. parainfluenzae H. paracuniculus H. parahaemolyticus H. paraphrohaemolyticus[1] H. pittmaniae H. piscium[1] H. sputorum[1] Haemophilus is a genus of Gram-negative, pleomorphic, coccobacilli bacteria belonging to the family Pasteurellaceae.

[4] The genus includes commensal organisms along with some significant pathogenic species such as H. influenzae—a cause of sepsis and bacterial meningitis in young children—and H. ducreyi, the causative agent of chancroid.

[6] They are unable to synthesize important parts of the cytochrome system needed for respiration, and they obtain these substances from the heme fraction of blood hemoglobin.

Clinical laboratories use tests for the hemin and NAD requirement to identify the isolates as Haemophilus species.

Chocolate agar is an excellent Haemophilus growth medium, as it allows for increased accessibility to these factors.