E. coli, usually verotocytotoxin producing - VTEC - found in 75% of cases of D+ HUS. Verocytotoxin will kill endothelial cells. In the UK 75% of VTEC found in faecal specimens have the serotype O157:H7, screened for at public health laboratories.
shigella, usually flexeri which produces a toxin similar to that produced by VTEC
autoimmunity and endotoxin causing a neutrophil leukocytosis have also been implicated.