STX2 and hemolytic-uremic syndrome: In 1996, an Stx2-positive E. cloacae strain was isolated from an HUS patient [62]; while PCR, DNA hybridization assays, and Vero cell cytotoxicity assays all confirmed that the strain produced an Stx2-type toxin, the presence of the stx2 gene seemed to be unstable as it could not be identified consistently in all subcultures.