V Factor Disc is used for the presumptive identification of Haemophilus species on the basis of their requirements for X or V factors or both.Both X and V factors are growth factors that are essential for certain organisms like Haemophilus species and also enhance growth of organisms like Neisseria species. Bordetella pertussis ATCC 8467 :Positive with X factor ; Haemophilus influenzae ATCC 35056: Negative