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

Operons of the afa family are expressed by pathogenic Escherichia coli stra ins associated,vith intestinal and extraintestinal infections in humans and animals, The recently demonstrated heterogeneity of these operons (L, Lali oui, M, Jouve, P, Gounon, and C, Le Bouguenec, Infect. Immun, 67:5048-5059, 1999) was used to develop a new PCR assay for detecting all the operons of the afa family with a single genetic tool. This PCR approach was validated by investigating three collections of human E. coli isolates originating f rom the stools of infants with diarrhea (88 strains), the urine of patients with pyelonephritis (97 strains), and the blood of cancer patients (115 st rains). The results obtained with this single test and those previously obt ained with several PCR assays were closely correlated. The AfaE adhesins en coded by the afa operons are variable, particularly with respect to the pri mary sequence encoded by the afaE gene. The receptor binding; specificities have not been determined for all of these adhesins; some recognize the Dr blood group antigen (Afa/Dr(+) adhesins) on the human decay-accelerating fa ctor (DAF) as a receptor, and others (Afa/Dr(-) adhesins) do not. Thus, the afa operons detected in this study were characterized by subtyping the afa E gene using specific PCRs, In addition, the DAF-binding capacities of as y et uncharacterized AfaE adhesins were tested by various cellular approaches . The afaE8 subtype (Afa/Dr- adhesin) was found to predominate in afa posit ive isolates from sepsis patients (75%); it was frequent in afa-positive py elonephritis E. coli (55.5%) and absent from diarrhea-associated strains. I n contrast, Afa/Dr(+) strains (regardless of the afaE subtype) were associa ted 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 an d the physiological site of the infection caused by afa-positive strains.