Identification of two new antigenic subgroups within the genus Mobiluncus.

Classifications of 48 atypical clinical isolates of Mobiluncus spp. were determined on the basis of biochemical reactions, morphology, antigenic profiles, and DNA hybridization studies. Two new subgroups with unique antigenic profiles are described. Like typical Mobiluncus species, the antigenic variant of M. mulieris is associated with bacterial vaginosis. The atypical isolates of M. curtisii were frequently recovered from women with normal vaginal flora and were also recovered from sterile body sites. These isolates may be incorrectly identified if current biochemical and morphological criteria are used for identification. Gram stain morphology, however, correctly identifies these isolates to the species level. The characterization of these atypical isolates has important implications for future investigations in which serological methods are used for diagnosis, epidemiology, and determination of pathogenicity of Mobiluncus spp.