Affiliation:
1. Unité de Pathogénie Bactérienne des Muqueuses, Groupe d'Etude des Infections Diarrhéiques (GEID)
2. Station Centrale de Microscopie Electronique, Institut Pasteur, 75724 Paris Cedex 15, France
Abstract
ABSTRACT
Enteroaggregative
Escherichia coli
(EAEC) is recognized as an emerging cause of diarrhea in children and adults worldwide, and recent studies have implicated EAEC in persistent diarrhea in patients infected with human immunodeficiency virus (HIV). In this study, we identified aggregative adhesion fimbria type III (AAF-III) in isolate 55989, a typical EAEC strain. Analysis of the sequence of the plasmid-borne
agg-3
gene cluster encoding AAF-III showed this cluster to be closely related to the
agg
and
aaf
operons and to the
afa
operons carried by diffusely adherent pathogenic
E. coli
. We investigated the adhesion properties of a collection of 25 EAEC strains isolated from HIV-infected patients presenting with persistent diarrhea. We found that a minority of strains (36%) carried sequences similar to those of the
agg
and
aaf
operons, which encode AAF-I and AAF-II, respectively. We developed PCR assays specific for the
agg-3
operon. In our collection, the frequency of AAF-III strains was similar (12%) to that of AAF-I strains (16%) but higher than that of AAF-II isolates (0%). Differences between EAEC strains in terms of the virulence factors present render detection of these strains difficult with the available DNA probes. Based on comparison of the
agg
,
aaf
, and
agg-3
operons, we defined an AAF probe internal to the adhesion gene clusters and demonstrated that it was efficient for the identification of EAEC strains. We investigated 32 EAEC isolates, of which only 34.4% were detected with the classical CVD432 probe (detecting pAA virulence plasmids) whereas 65.6% were detected with the AAF probe.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Cited by
186 articles.
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