Purification of an Escherichia coli serogroup O157:H7 verotoxin and its detection in North American hemorrhagic colitis isolates.

Verotoxin (VT), which is immunologically unrelated to VT1 (Shiga-like toxin I), was purified from the culture filtrate of Escherichia coli hemorrhagic colitis serogroup O157:H7 strain 3657 by copper ion chelate affinity chromatography followed by anion-exchange chromatography. The isoelectric point by sucrose density gradient isoelectric focusing was 5.0, the molecular weight by gel filtration on Superose 12 was about 60,000, and the 50% cytopathic dose for Vero cells was about 1 pg. This toxin was found by immunological methods to be the predominant VT in E. coli O157 isolates associated with illness in North America, with 38 of 42 strains tested producing this toxin, 20 in combination with VT1. VT from strain 3657 is immunologically identical to the described Shiga-like toxin II (VT2) of E. coli strains (from the United States) K-12(pEB1) and C600(933W) but only partially related to VT of strain E32511 (from the United Kingdom), the first to be named VT2.