Abstract
Antigenic relationships among type-1 fimbriae of 40 strains of Enterobacteriaceae representing 19 species and seven genera were determined by immuno-electronmicroscopy. Ten distinct antigenic groups were distinguished. Intra- and inter-generic relationships were observed although some antigenic groups were species-specific only. Antigenic relationships among type-1 fimbriae are more complex than have been reported hitherto.