[en] Virulence factors and phenotypes of 61 strains CNF1+ were investigated. Eighty-nine percent of the strains produced an aerobactin and were resistant to the bactericidal activity of sheep serum, both of which are properties of septicemic strains of E coli. None of the strains reacted either with DNA probes corresponding to the enterotoxins STaP, STb, LT-I and LT-IIa, or to the verotoxins VT-I and VT-II. None produced the adhesins K99, Att25 (FY or F17) and Att111. The great majority (93.4%) of the CNF1+E coli possessed both properties. These properties allow CNF1+ to be distinguished from CNF-E coli.