CD59 and cholesteryl ester measurement: Despite there being no virulence factors present in all non-CE isolates, protectins (hha, espA, espB, espF, espJ, and etpD), toxin (stx2b-O174-031), iron uptake (ireA), and invasion (tia) virulence factors were often present (<43%) in non-CE isolates and absent in all CE isolates.