Laboratory definitive evidence for a confirmed case requires evidence of shiga toxin, which comprises either:

• culture and isolation of shiga toxin-producing Escherichia coli
• PCR detection of the genes (stx1 and/or stx2) associated with the production of shiga toxin in E. coli.

All isolates should be referred to the Enteric Reference Laboratory at ESR for further characterisation.

Isolates producing shiga toxin 2 (stx2) are more likely to cause serious human disease than isolates producing shiga toxin 1 (stx1) or both toxins together.

Note: The eae (intimin) and hlyA (enterohaemolysin) genes are accessory virulence factors strongly associated with enterohaemorrhagic E. coli (EHEC). However, finding these genes without the presence of a stx gene does not constitute a positive toxin test.