CHARACTERIZATION OF THE LOCUS OF ENTEROCYTE EFFACEMENT (LEE) IN DIFFERENT ENTEROPATHOGENIC ESCHERICHIA-COLI (EPEC) AND SHIGA-TOXIN PRODUCING ESCHERICHIA-COLI (STEC) SEROTYPES

All proteins involved in the attachment and effacement lesion produced by enteropathogenic Escherichia coli (EPEC) and Shiga-toxin producing E. toll (STEC) are encoded by the locus of enterocyte effacement (LEE ). We studied the presence and insertion site of the LEE in different EPEC and STEC strains. In serotypes O119:H6/H-, O55:H6, O55,H7, 0142:H 6, O111ac:H9/H-, O111ab:H9/H- LEE is inserted downstream of selC as pr eviously described for EPEC O127:H6 and STEC O157:H7. In serotypes O11 1ac:H8/H- and O26:H11/H- the LEE is inserted in pheU as previously des cribed for STEC O26:H-. However in EPEC from serotype O111ab:H25 the L EE is not inserted in either site suggesting a third insertion site in the K12 chromosome. We also cloned fragments of 2.3 kb and 1.0 kb fro m the right and left hand sides of the LEE of a O111ac:H- strain and i dentified additional insertion sequences on these LEE fragments, sugge sting that the LEE may be larger and may have undergone more recombina tion events in these serotypes. (C) 1998 Federation of European Microb iological Societies. Published by Elsevier Science B.V. All rights res erved.