DIFFERENCES BETWEEN PATHOTYPES AND SEROGR OUPS OF VEROTOXIN-PRODUCINGESCHERICHIA-COLI STRAINS (VTEC) ISOLATED FROM DIARRHEIC OR HEALTHY CALVES

Differences between pathotypes and serogroups of verotoxin producing E scherichia coli strains (VTEC) isolated from diarrhoeic or healthy cal ves. One hundred and eighteen VTEC isolates from cattle were studied b y pathotyping and serotyping. These VTEC are very heterogeneous. The d etection of genes responsible for the production of verotoxins 1 and 2 (SLT1 and SLT2) and for the production of intimin EaeA make it possib le to classify these strains in five different pathotypes. In addition serotyping demonstrates the existence of 30 different groups. VTEC ar e isolated from diarrhoeic and also from healthy cattle; but strains i solated from diarrhoeic or healthy animals are quite different. The fi rst isolates generally display the pathotype SLT1+/EaeA+ and belong ma inly to serogroups O26, O111, O118 and rough/H11 or H16. The latter di splay more often the pathotype SLT2+/EaeA- and there are no predominan t serogroups among these. It seems that the production of verotoxin by a strain of E. coli is not sufficient to assess his possible pathogen icity.