Characteristics of necrotoxigenic Escherichia coli isolated from septicemic and diarrheic calves between 1958 and 1970

A total of 434 Escherichia coli isolated from septicemic calves between 195 8 and 1965 and 430 E. coli isolated from diarrheic calves between 1967 and 1970 were studied by colony hybridisation and PCR assays for the presence o f the cnf1- and the cnf2-like genes. They were also studied for the presenc e of genes coding for putative virulence factors associated with the CNF to xins including F17-, Pap- and Sfa-fimbrial adhesins and the recently descri bed CDT-III toxin and AfaVIII-afimbrial adhesin. Thirty (7%) of the 434 sep ticemic strains were positive for CNF by colony hybridisation. Twenty-six w ere confirmed as necrotoxigenic E. coli type 2 (NTEC2) and four as NTEC1 by PCR. Thirty-five (8%) of the 430 diarrheic strains were positive for CNF b y colony hybridisation. Five of them were studied by PCR and confirmed as N TEC1. The 26 septicemic NTEC2 strains and 20 of the 35 diarrheic NTEC inclu ding three of the five NTEC1 were positive for CDT-III. All adhesins studie d were present in NTEC as well as in non-NTEC. NTEC1 were mainly Pap-, Sfa- and/or Afa8-positive, whereas NTEC2 were mainly F17- and/or Afa8-positive. This study shows that necrotoxigenic E. coli with their associated adhesin s and toxins were present in calves as early as 1958, but their prevalence seems to have increased since that time. (C) 2001 Elsevier Science B.v. All rights reserved.