Abstract
Antigenic relationships among type-3 fimbriae of 31 strains, representing 19 species and eight genera of Enterobacteriaceae, were investigated by immunoelectronmicroscopy in tests with 17 different type-3 fimbrial antisera. At least nine antigenically distinct groups among type-3 fimbriae were distinguished. The constituent membership of some groupings did not conform with current views on the taxonomy of Enterobacteriaceae.