Cytopathogenicity of Mycoplasma fermentans (Including Strain Incognitus)

Mycoplasma fermentans strain incognitus, an organism recently identified in tissues of patients with AIDS and in tissues of otherwise healthy adults with an acute fatal respiratory disease, was evaluated for cytopathogenicity for tracheal tissue in vivo and in vitro. In this study, the organism produced a chronic infection of the lower respiratory tract in LEW rats following intranasal inoculation and induced both ciliostasis and cytopathology in experimentally infected tracheal explants from rats. The time of onset of ciliostasis, type of cytopathogenicity, and localization of organism in strain incognitus were different from those in other strains of M. fermentans as well as other species of mycoplasmas isolated from humans. The results strongly support, but do not prove, that M. fermentans strain incognitus is an unusually invasive mycoplasma, as it was the only strain found within respiratory epithelial cells both in vivo and in vitro. Detection of the organism within the lamina propria also supported the organism's invasive potential. Further study of both the in vivo and in vitro models should provide insights into this potentially unique mycoplasma-host relationship.