Haemagglutinins and fimbriae of Morganella, Proteus and Providencia.

One hundred and thirteen strains of Morganella, Proteus and Providencia, grown in different cultural conditions, were examined for their ability to produce haemagglutinins (HAs). Three main kinds of HA (MS, MR/K and MR/P) were detected, and 89% of the 112 HA+ strains were capable of producing two or three of the different HAs in the same or different cultures. The properties of the three HAs were partly defined and the difficulties of identifying their separate HA activities when present together are discussed. Electronmicroscopic examination of bacteria from HA+ cultures showed at least six distinct fimbrial types, the properties of which are described. We tried, with limited success, to correlate the presence of the different HAs with that of the different fimbrial types. The significance of our findings is reviewed in the light of recent taxonomic changes for this group of enterobacteria. The distribution of HAs and fimbriae in the species of Morganella, Proteus and Providencia is more complex than that so far described for other genera of Enterobacteriaceae.