ABSTRACT
This chapter reviews the early observations of fimbrial adhesins in enterobacteria, which provided the background to later studies with newer, more powerful techniques and revealed difficulties to be overcome, pitfalls to be avoided, and complexities to be resolved. Fimbriae with the same morphology and hemagglutinating pattern as those in E.coli group 1 were later found in most strains of Shigella flexneri, Klebsiella pneumoniae, Salmonella, Serratia marcescens, Entero-bacter cloacae, and Citrobacter freundii and some of Morganella, Proteus, and Providencia. The definition of type 1 fimbriae was thus based on their morphology and the characteristic wide spectrum and D-mannose sensitivity of their hemagglutinating and adhesive properties, but fimbriae so defined are not identical in all different bacteria. Phase variations have since been described for other adhesins: changes between adhesive and nonadhesive phases and changes between phases in which different adhesins are expressed.
