Characterization of AfaE Adhesins Produced by Extraintestinal and Intestinal Human Escherichia coli Isolates: PCR Assays for Detection of Afa Adhesins That Do or Do Not Recognize Dr Blood Group Antigens

Abstract

adhesins) on the human decay-accelerating factor (DAF) as a receptor, and others (Afa/Dr؊ adhesins) do not. Thus, the afa operons detected in this study were characterized by subtyping the afaE gene using specific PCRs. In addition, the DAF-binding capacities of as-yet-uncharacterized AfaE adhesins were tested by various cellular approaches. The afaE8 subtype (Afa/Dr ؊ adhesin) was found to predominate in afa-positive isolates from sepsis patients (75%); it was frequent in afa-positive pyelonephritis E. coli (55.5%) and absent from diarrhea-associated strains. In contrast, Afa/Dr ؉ strains (regardless of the afaE subtype) were associated with both diarrhea (100%) and extraintestinal infections (44 and 25% in afa-positive pyelonephritis and sepsis strains, respectively). These data suggest that there is an association between the subtype of AfaE adhesin and the physiological site of the infection caused by afa-positive strains.

Mecanismos de virulencia de Escherichia coli enteropatógena

“…Algunas de las proteínas implicadas en la virulencia de ECST, principalmente en algunas del T3SS, las subuniLas cepas de ECAD expresan adhesinas afimbriales (Afa) y adhesinas fimbriales (Dr). Estas adhesinas se encuentran en la superficie de la membrana externa de la bacteria, confiriendo el principal mecanismo de patogenicidad 122,123 . Se subdividen en dos clases, la típica Afa/DrECAD y la atípica Afa/DrECAD que tienen como características la misma organización genética y la unión al factor de aceleración (hDAF: human decayaccelerating factor) 124 .…”

Interleukin‐8 Secretion by Epithelial Cells Infected with Diffusely Adherent Escherichia coli Possessing Afa Adhesin‐Coding Genes

“…DAEC strains were assigned to subgroups according to the scheme described by Le Bouguénec et al (34). Organisms that did not react with primers for any afa subtypes but reacted with the primer set for afaBC were classified as afaEX: the bacteria possessed genes amplified with primers for Afa/Dr but the gene was not identified as part of a particular subgroup.…”

“…French groups have continued to investigate these Afa-positive DAEC and have provided information regarding their molecular bacteriology (2,(14)(15)(16)(31)(32)(33)(34). Furthermore, Bétis et al (3,4) found that two DAEC strains induced interleukin-8 (IL-8) in human colonic epithelial cell line, T84.…”

“…This Dr antigen consists of the exposed domain of the decay-accelerating factor (DAF) (52). Although F1845 initially was found as a fimbria unique to DAEC (5), Dr adhesins (Dr, DrII, Afa-I, and Afa-III), including F1845, are encoded on the same gene clusters and are considered to be subtypes of Afa (34).…”

High Resolution Studies of the Afa/Dr Adhesin DraE and Its Interaction with Chloramphenicol

“…Although these adhesins differ in sequence, they all bind to the third CCP domain of DAF with the exception of AfaE-VII and AfaE-VIII (18). Two of the Afa/Dr adhesins, AfaE-III and DraE, differ in sequence by only three amino acids but possess significantly different properties.…”