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Infection and Immunity, March 2000, p. 1587-1599, Vol. 68, No. 3
Medical Service, VA Medical Center, and
Department of Medicine, University of Minnesota, Minneapolis,
Minnesota1; International
Escherichia and Klebsiella Center, World Health
Organization, Copenhagen, Denmark2;
Medical Service, VA Medical Center, and Department of Medicine,
State University of New York at Buffalo, Buffalo, New
York3; and Department of Bacteriology,
Institute of Infectious Diseases and Immunology, Faculty of
Veterinary Medicine, University of Utrecht, Utrecht, The
Netherlands4
Received 8 October 1999/Returned for modification 16 November
1999/Accepted 15 December 1999
Polymorphisms in PapA, the major structural subunit and antigenic
determinant of P fimbriae of extraintestinal pathogenic Escherichia coli, are of considerable epidemiological,
phylogenetic, and immunotherapeutic importance. However, to date, no
method other than DNA sequencing has been generally available for their detection. In the present study, we developed and rigorously validated a novel PCR-based assay for the 11 recognized variants of
papA and then used the new assay to assess the prevalence,
phylogenetic distribution, and bacteriological associations of the
papA alleles among 75 E. coli isolates from
patients with urosepsis. In comparison with conventional F serotyping,
the assay was extremely sensitive and specific, evidence that
papA sequences are highly conserved within each of the
traditionally recognized F serotypes despite the diversity observed
among F types. In certain strains, the assay detected serologically
occult copies of papA, of which some were shown to
represent false-negative serological results and others were shown to
represent the presence of nonfunctional pap fragments.
Among the urosepsis isolates, the assay revealed considerable segregation of papA alleles according to O:K:H serotype,
consistent with vertical transmission within clones, but with
exceptions which strongly suggested horizontal transfer of
papA alleles between lineages. Sequencing of
papA from two strains that were papA positive by probe and PCR but F negative in the new PCR assay led to the discovery of two novel papA variants, one of which was
actually more prevalent among the urosepsis isolates than were several of the known papA alleles. These findings provide novel
insights into the papA alleles of extraintestinal
pathogenic E. coli and indicate that the F PCR assay
represents a versatile new molecular tool for epidemiological and
phylogenetic investigations which should make rapid, specific detection
of papA alleles available to any laboratory with PCR capability.
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Analysis of the F Antigen-Specific papA
Alleles of Extraintestinal Pathogenic Escherichia coli
Using a Novel Multiplex PCR-Based Assay
*
Corresponding author. Mailing address: Infectious
Diseases (111F), Minneapolis VA Medical Center, 1 Veterans Dr.,
Minneapolis, MN 55417. Phone: (612) 725-2000, ext. 4185. Fax: (612)
725-2273. E-mail: johns007{at}maroon.tc.umn.edu.
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