Type 1 fimbrial expression enhances Escherichia coli virulence for the urinary tract.
Type 1 fimbriae are adhesion organelles expressed by many Gram-negative bacteria. They facilitate adherence to mucosal surfaces and inflammatory cells in vitro, but their contribution to virulence has not been defined. This study presents evidence that type 1 fimbriae increase the virulence of Escherichia coli for the urinary tract by promoting bacterial persistence and enhancing the inflammatory response to infection. In a clinical study, we observed that disease severity was greater in children infected with E. coli O1:K1:H7 isolates expressing type 1 fimbriae than in those infected with type 1 negative isolates of the same serotype. The E. coli O1:K1:H7 isolates had the same electrophoretic type, were hemolysin-negative, expressed P fimbriae, and carried the fim DNA sequences. When tested in a mouse urinary tract infection model, the type 1-positive E. coli O1:K1:H7 isolates survived in higher numbers, and induced a greater neutrophil influx into the urine, than O1:K1:H7 type 1-negative isolates. To confirm a role of type 1 fimbriae, a fimH null mutant (CN1016) was constructed from an O1:K1:H7 type 1-positive parent. E. coli CN1016 had reduced survival and inflammatogenicity in the mouse urinary tract infection model. E. coli CN1016 reconstituted with type 1 fimbriae (E. coli CN1018) had restored virulence similar to that of the wild-type parent strain. These results show that type 1 fimbriae in the genetic background of a uropathogenic strain contribute to the pathogenesis of E. coli in the urinary tract.
Connell
I
I
Department of Medical Microbiology, Lund University, Sweden.
Agace
W
W
Klemm
P
P
Schembri
M
M
Mărild
S
S
Svanborg
C
C
D000818:Animals; D015139:Blotting, Southern; D002648:Child; D004269:DNA, Bacterial / Q000737:chemistry; D004926:Escherichia coli / Q000472:pathogenicity* / Q000648:ultrastructure; D004927:Escherichia coli Infections / Q000382:microbiology*; D005838:Genotype; D006801:Humans; D051379:Mice; D016253:Microscopy, Immunoelectron; D009693:Nucleic Acid Hybridization; D010641:Phenotype; D018933:Pili, Sex / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism*; D015183:Restriction Mapping; D014552:Urinary Tract Infections / Q000382:microbiology*
D004269:DNA, Bacterial; D011971:Receptors, Immunologic; C076610:fimbriae receptor, type 1