dothelial homeostasis, leading to HUS. However, recent reports on the association between HUS and Stx-negative E. coli strains [2] suggest that additional determinants of EHEC may also contribute to HUS development. Certainly, only a portion of Stx-producing bacteria are able to cause HUS. Therefore, it is necessary to differentiate such EHEC strains from a large variety of other STEC strains that have not been associated with severe disease in humans, including HUS. For the latter strains, we propose the designation LP-STEC (i.e., low-pathogenic Stx-producing E. coli).