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Journal of Clinical Microbiology, May 2001, p. 1738-1745, Vol. 39, No. 5
0095-1137/01/$04.00+0   DOI: 10.1128/JCM.39.5.1738-1745.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

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

Chantal Le Bouguénec,1,* Lila Lalioui,1 Laurence du Merle,1 Mabel Jouve,1,2 Pascale Courcoux,1 Saeid Bouzari,1,dagger Rangaraj Selvarangan,3 Bogdan J. Nowicki,3 Yves Germani,4 Antoine Andremont,5 Pierre Gounon,2 and Marie-Isabelle Garcia1,Dagger

Unité de Pathogénie Bactérienne des Muqueuses1 and Station Centrale de Microscopie Electronique,2 Institut Pasteur, 75724 Paris Cedex 15, and Unité de Bactériologie, INSERM EMI 9933, Hôpital Bichat, AP-PH, Paris,5 France; Department of Microbiology and Immunology and Department of Obstetrics and Gynecology, The University of Texas Medical Branch, Galveston, Texas 775553; and Unité des Maladies Infectieuses Opportunistes, Institut Pasteur de Bangui, BP923 Bangui, Central African Republic4

Received 18 October 2000/Returned for modification 20 December 2000/Accepted 5 February 2001

Operons of the afa family are expressed by pathogenic Escherichia coli strains associated with intestinal and extraintestinal infections in humans and animals. The recently demonstrated heterogeneity of these operons (L. Lalioui, M. Jouve, P. Gounon, and C. Le Bouguénec, 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 from the stools of infants with diarrhea (88 strains), the urine of patients with pyelonephritis (97 strains), and the blood of cancer patients (115 strains). The results obtained with this single test and those previously obtained with several PCR assays were closely correlated. The AfaE adhesins encoded by the afa operons are variable, particularly with respect to the primary 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 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.

* Corresponding author. Mailing address: Unité de Pathogénie Bactérienne des Muqueuses, Institut Pasteur, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France. Phone: (1) 40 61 32 80. Fax: (1) 40 61 36 40. E-mail: clb{at}pasteur.fr.

dagger Present address: Molecular Biology Unit, Pasteur Institute of Iran, Teheran 13164, Iran.

Dagger Present address: Università di Roma `La Sapienza,' Dipartimento di biotecnologie cellulari ed Ematologie, Sezione di Genetica Molecolare, 1-00161 Rome, Italy.

Journal of Clinical Microbiology, May 2001, p. 1738-1745, Vol. 39, No. 5
0095-1137/01/$04.00+0   DOI: 10.1128/JCM.39.5.1738-1745.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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