An X-factor Requiring Haemophilus Species Ryan, W. J.,, 52, 275-286 (1968), doi = https://doi.org/10.1099/00221287-52-2-275, publicationName = Microbiology Society, issn = 1350-0872, abstract= SUMMARY: The isolation from a perianal abscess of a Haemophilus species requiring for growth the presence of X-factor but not V-factor is recorded. Two other similar strains were isolated from normal faeces. The properties of these isolates are given and compared with those of previously described species of the genus Haemophilus having the same growth requirements. The isolates form a homogeneous group resembling Haemophilus influenzae-murium., language=, type=