Microbiologic, microscopic, and ultrastructural studies have demonstrated at least three different types of diphtheroids in granules of trichomycosis axillaris. These have similar morphology but yield different colony types and have different growth requirements on culture. Bacterial growth is confined to the hair cuticle. In vitro reproduction of lesions on normal hair using pure cultures of isolated strains has been accomplished.
Freeman RG, McBride ME, Knox JM. Pathogenesis of Trichomycosis Axillaris. Arch Dermatol. 1969;100(1):90-95. doi:10.1001/archderm.1969.01610250096022