Walsh & Hoyt: Haemophilus

Members of the genus Haemophilus (from the Greek words, Haema, meaning ""blood,"" and philos, meaning ""fond of"") are small, pleomorphic, slow-growing, gram-negative coccobacilli. The name is derived from the requirement of the organisms for a variety of growth factors, all of which can be supplied by erythrocytes. Most Haemophilus species are part of the normal flora of the mouth and upper respiratory tract. The most common species of Haemophilus associated with neurologic infection is H. influenzae, but other species, including H. parainfluenzae, H. aphrophilus, and H. paraphrophilus can also infect the CNS.