Most well known type. 0157:h7 is the most common 'genetic strain' of disease producing shiga toxin producing E. coli in the US. It is most often introduced into individuals through contaminated food that is undercooked. It was also believed to be the most likely variant associated with severe illness, however the outbreak in Germany last year of severe STEC was from a different strain, known as 0104:h4.
EHEC. O157 is the classical pathotype of enterohemorrhagic e. Coli (ehec). There are other shiga toxin producing e. Coli that can cause the same serious sequelae of hemolytic uremic syndrome as well that need to be screened for using a shiga toxin gene assay instead the more available sorbitol-macconkey agar which only detects o157.