Inability of encapsulated Klebsiella pneumoniae to assemble functional type 1 fimbriae on their surface

We screened phase variants of Klebsiella pneumoniae isolates for the expres sion of capsule and type 1 fimbriae and found that all of the 22 blood isol ates were encapsulated and did not express type 1 fimbriae while 10 of 11 u rinary tract isolates expressed type 1 fimbriae but were unencapsulated. Ph ase variants from selected isolates were found to be either unencapsulated and fimbriated or lacked both structures. Variants expressing both structur es were not detected. Fimbrial subunits FimH and FimA were localized in the periplasmic space of the parent strain and on the surface of the unencapsu lated variants. The results suggest that capsule formation impedes assembly of pie-formed fimbrial subunits on the bacterial surface. (C) 1999 Publish ed by Elsevier Science B.V. All rights reserved.