title: Characterization of plasmid-borne afa-3 gene clusters encoding afimbrial adhesins expressed by Escherichia coli strains associated with intestinal or urinary tract infections.
abstract: The afa gene clusters encode afimbrial adhesins (AFA) that are expressed by uropathogenic and diarrhea-associated Escherichia coli strains and belong to a family of hemagglutinins recognizing the Dr blood group antigen as a receptor. This family so far includes AFA-I and AFA-III as well as the Dr and F1845 adhesins (B. Nowicki, A. Labigne, S. Moseley, R. Hull, S. Hull, and J. Moulds, Infect. Immun. 58:279-281, 1990). Reported in this work is the genetic organization of the afa-3 gene cluster cloned from a uropathogenic E. coli strain (A30) which expressed a subtype of AFA designated AFA-III. The amino acid sequence of AFA-III was deduced from the nucleotide sequence of the afaE3 gene and was found to be highly homologous to that of the Dr adhesin (98.1% identity). A polymerase chain reaction assay was developed to detect the presence of afa-3 gene clusters in E. coli strains. Study of the genetic support of the afa-3 gene clusters in the strains which showed positive amplification revealed that they were always located on large, 100-kb plasmids whether the strains originated from patients with cystitis or with diarrhea. Moreover, the cloned afa-3 gene clusters from A30 and from the diarrhea-associated strain AL845 appeared to be carried by 9-kb plasmid regions which displayed a similar genetic organization. Chloramphenicol was reported to be a potent inhibitor of receptor binding by the Dr adhesin (Nowicki et al., Infect. Immun. 58:279-281, 1990). AFA-III expressed by strains AL845 and AL847 appeared to mediate, like the Dr adhesin, chloramphenicol-sensitive hemagglutination, whereas AFA-III produced by A30 conferred chloramphenicol-resistant adherence. A comparison of the sequences of these four proteins indicated that the amino acid at position 52 of the processed AFA could be part of the receptor-binding domain.
authors.affiliation: Unité des Entérobactéries, Institut National de la Santé et de la Recherche Médicale U199, Paris, France.
authors.forename: C
authors.initials: C
authors.lastname: Le Bouguenec
authors.forename: M I
authors.initials: MI
authors.lastname: Garcia
authors.forename: V
authors.initials: V
authors.lastname: Ouin
authors.forename: J M
authors.initials: JM
authors.lastname: Desperrier
authors.forename: P
authors.initials: P
authors.lastname: Gounon
authors.forename: A
authors.initials: A
authors.lastname: Labigne
mesh_terms: D018830:Adhesins, Escherichia coli; D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000235:genetics*; D001422:Bacterial Adhesion / Q000235:genetics; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000472:pathogenicity / Q000648:ultrastructure; D015870:Gene Expression; D005798:Genes, Bacterial; D006801:Humans; D007410:Intestinal Diseases / Q000382:microbiology; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D005810:Multigene Family; D010957:Plasmids; D015183:Restriction Mapping; D014552:Urinary Tract Infections / Q000382:microbiology
chemical_list: D018830:Adhesins, Escherichia coli; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D004269:DNA, Bacterial