Characterization of the Type 3 Fimbrial Adhesins of Klebsiella Strains

The Klebsiella pneumoniae fimbrial adhesin, MrkD, mediates adherence to the basolateral surfaces of renal and pulmonary epithelia and to the basement membranes of tissues. Although all isolates possessing the MrkD adhesin mediate the agglutination, in vitro, of erythrocytes treated with tannic acid, the mrkD gene is not conserved within species. The ability of a plasmid-borne mrkD gene product to mediate binding to type V collagen is associated frequently with strains of K. oxytoca and rarely with strains of K. pneumoniae. In K. pneumoniae, the MrkD adhesin is located within a chromosomally borne gene cluster and mediates binding to collagen types IV and V. The plasmid-borne determinant, mrkD(1P), and the chromosomally borne gene, mrkD(1C), are not genetically related. Some strains of enterobacteria possess a mrkD(1C) allele that is associated with hemagglutinating activity but does not bind to either type IV or type V collagen.