Commensal and pathogenic Escherichia coli use a common pilus adherence factor for epithelial cell colonization

doi:10.1073/pnas.0704104104

Commensal and pathogenic Escherichia coli use a common pilus adherence factor for epithelial cell colonization

*Department of Immunobiology, University of Arizona, 1501 North Campbell Avenue, Tucson, AZ 85724;
^†Centro de Ciências da Saúde Centro Universitário Maranhão, Rua Josué Montelo No. 1, São Luís 65075-120, Maranhão, Brazil;
^‡Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México; and
^§Department of Microbiology and Immunology, University of Maryland School of Medicine, 685 West Baltimore Street, Baltimore, MD 21201

Communicated by Roy Curtiss, Arizona State University, Tempe, AZ, May 2, 2007 (received for review August 4, 2006)

Abstract

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a food-borne pathogen that causes hemorrhagic colitis and the hemolytic uremic syndrome. Colonization of the human gut mucosa and production of potent Shiga toxins are critical virulence traits of EHEC. Although EHEC O157:H7 contains numerous putative pili operons, their role in the colonization of the natural bovine or accidental human hosts remains largely unknown. We have identified in EHEC an adherence factor, herein called E. coli common pilus (ECP), composed of a 21-kDa pilin subunit whose amino acid sequence corresponds to the product of the yagZ (renamed ecpA) gene present in all E. coli genomes sequenced to date. ECP production was demonstrated in 121 (71.6%) of a total of 169 ecpA ⁺ strains representing intestinal and extraintestinal pathogenic as well as normal flora E. coli. High-resolution ultrastructural and immunofluorescence studies demonstrated the presence of abundant peritrichous fibrillar structures emanating from the bacterial surface forming physical bridges between bacteria adhering to cultured epithelial cells. Isogenic ecpA mutants of EHEC O157:H7 or fecal commensal E. coli showed significant reduction in adherence to cultured epithelial cells. Our data suggest that ECP production is a common feature of E. coli colonizing the human gut or other host tissues. ECP is a pilus of EHEC O157:H7 with a potential role in host epithelial cell colonization and may represent a mechanism of adherence of both pathogenic and commensal E. coli.

Footnotes

^¶To whom correspondence should be addressed. E-mail: jagiron{at}email.arizona.edu
Author contributions: Z.S. and A.L.E. contributed equally to this work; M.A.R., J.B.K., J.L.P., and J.A.G. designed research; M.A.R., Z.S., A.L.E., V.M.-N., and A.V. performed research; J.B.K. and J.L.P. contributed new reagents/analytic tools; M.A.R., Z.S., A.L.E., J.L.P., and J.A.G. analyzed data; and J.L.P. and J.A.G. wrote the paper.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/cgi/content/full/0704104104/DC1.
Abbreviations:

AE,

attaching and effacing;

EHEC,

enterohemorrhagic E. coli;

ECP,

E. coli common pilus;

HUS,

hemolytic uremic syndrome;

IB,

immunoblotting;

IF,

immunofluorescence;

NFEC,

normal flora E. coli;

STEC,

Shiga-toxigenic E. coli.
Freely available online through the PNAS open access option.