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Infect. Immun., May 1995, 1663-1668, Vol 63, No. 5
T Pham, A Kaul, A Hart, P Goluszko, J Moulds, S Nowicki, DM Lublin and BJ Nowicki
Bacterial adhesins are important virulence factors that allow colonization
of the human urogenital tract by Escherichia coli. Adhesins of the Dr
family have been found to be more frequently expressed in strains
associated with symptomatic urinary tract infections. Because of the high
frequency of symptomatic urinary tract infections during pregnancy, we
screened E. coli isolates from 64 gestational pyelonephritis patients for
the expression of Dr and X adhesins to address their potential virulence
roles in this population. Using PCR and primers for the afaB gene, we
detected dra-related operons in 17 isolates (27%). On the basis of the lack
of hemagglutination of Dr(a-) erythrocytes containing a point mutation in
the decay-accelerating factor (DAF) short consensus repeat-3 (SCR-3)
domain, 12 of these strains were categorized as classical Dr adhesins. The
hemagglutination of O erythrocytes by Dr+ strains was blocked or reduced by
a monoclonal antibody to the DAF SCR-3 domain. The remaining five
dra-positive strains agglutinated Dr(a-) erythrocytes. Monoclonal antibody
to the DAF SCR-3 domain failed to block O-erythrocyte hemagglutination.
Adhesins in these strains did not fulfill criteria for Dr hemagglutinins
because of the undefined receptor specificities and were categorized as X.
E. coli strains bearing dra-related X adhesins bound to DAF
cDNA-transfected Chinese hamster ovary cells. Three of these dra-related
X-adhesin-bearing E. coli strains failed to attach to the SCR-3 delta
deletion transfectant, which suggested that binding sites were located in
the SCR-3 domain but outside the region blocked by the monoclonal
anti-SCR-3 immunoglobulin G. The binding sites of the remaining two
dra-related X adhesin strains were localized to the SCR-4 domain, as the
attachment was shown to be abolished on an SCR-4 delta mutant but
unaffected by an SCR-3 delta deletion. The heterogeneity in the binding
sites of E. coli DAF (Dr) family adhesins from gestational pyelonephritis
isolates may reflect the ability of the adhesins to evolve to recognize
alternate peptide epitopes for efficient colonization.
Copyright © 1995, American Society for Microbiology
dra-related X adhesins of gestational pyelonephritis-associated Escherichia coli recognize SCR-3 and SCR-4 domains of recombinant decay- accelerating factor
Department of Microbiology & Immunology, University of Texas Medical Branch at Galveston 77555, USA.
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