ABSTRACT
Type 3 fimbriae mediate a mannose-resistant hemagglutination of tannic acid-treated erythrocytes and were first described by Duguid. The term mannose-resistant, Klebsiella-like (MR/K) hemagglutinin has been used to describe this fimbrial adhesin because it was initially characterized in strains of Klebsiella. Type 3 fimbriae are produced by many members of the Enterobacteriaceae and are commonly detected on isolates of Enterobacter, Serratia, Proteus, and Providencia. The nucleotide sequences of the genes encoding the phenotypic expression of type 3 fimbriae, produced by a strain of K.pneumoniae, have been determined. The mrkF gene is involved in maintaining the stability of the fimbrial appendage upon the bacterial surface. Initial evidence indicates that at least some type 3 fimbriate bacteria can adhere to extracellular matrices and localize to the basement membrane of specific tissues. Examination of putative target proteins, located in extracellular matrices and as constituents of the basement membrane, indicated that E. coli transformants bound efficiently to type V collagen.
