Abstract

We examined the role of Klebsiella fimbrial types 1 and 3 in mediating adherence to human buccal and tracheal cells and to lung tissue sections. We found that clinical isolates of Klebsiella pneumoniae producing type 3 fimbriae and Escherichia coli HB101 containing a recombinant plasmid encoding expression of Klebsiella type 3 fimbriae (pFK10) demonstrated increased adherence to tracheal cells, trypsinized buccal cells, and lung tissue sections, in contrast to nonfimbriate and to type 1 fimbriate bacteria. Adherence by type 3 fimbriate bacteria was inhibited by purified type 3 fimbriae and Fab fragments derived from type 3 fimbrial-specific polyclonal immunoglobulin G. Type 3 fimbriae mediated attachment to the basolateral surface of tracheal cells and to the basal epithelial cells and the basement membrane regions of bronchial epithelia. Using an E. coli transformant (pDC17/pFK52), which expresses nonadherent P fimbrial filaments, along with the type 3 fimbrial adhesin (MrkD), we demonstrated that type 3 fimbrial attachment to respiratory cells was attributable to the MrkD adhesin subunit. Subsequent experiments demonstrated that the epithelial target of the type 3 fimbrial adhesin was most likely a peptide molecule rather than a carbohydrate. The results of this study demonstrate that, in vitro, the Klebsiella type 3 fimbrial adhesin mediates adherence to human respiratory tissue.