Identification of an aggregative adhesion fimbria (AAF) type III-encoding operon in enteroaggregative Escherichia coli as a sensitive probe for detecting the AAF-encoding operon family.
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.
Unité de Pathogénie Bactérienne des Muqueuses, Groupe d'Etude des Infections Diarrhéiques (GEID), Institut Pasteur, 75724 Paris Cedex 15, France.
Christine
C
Bernier
Pierre
P
Gounon
Chantal
C
Le Bouguénec
D017088:AIDS-Related Opportunistic Infections / Q000382:microbiology*; D018830:Adhesins, Escherichia coli / Q000235:genetics*; D000328:Adult; D000595:Amino Acid Sequence; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D015342:DNA Probes; D004269:DNA, Bacterial; D003967:Diarrhea / Q000382:microbiology*; D004926:Escherichia coli; D004927:Escherichia coli Infections / Q000382:microbiology*; D029968:Escherichia coli Proteins; D036781:Fimbriae Proteins; D010861:Fimbriae, Bacterial; D006367:HeLa Cells; D006388:Hemagglutinins / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D005810:Multigene Family; D009876:Operon; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
C108511:AafA protein, E coli; D018830:Adhesins, Escherichia coli; C079725:AggA protein, E coli; D001426:Bacterial Proteins; D015342:DNA Probes; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D006388:Hemagglutinins; C091070:afa-3 protein, E coli; C464642:aggregative adherence fimbria III, E coli; D036781:Fimbriae Proteins