The present invention provides a polypeptide, called EspA, which is secreted by pathogenic E. coli, such as the enteropathogenic (SPEC) and enterohemorrhagic (EHEC) E. coli. The invention also provides isolated nucleic acid sequences encoding EspA polypeptide, EspA peptides, a recombinant method for producing recombinant EspA, antibodies which bind to EspA, and a kit for the detection of EspA-producing E. coli.