Verification of Foodproof EHEC Screening by Real-Time PCR

Introduction: Foodborne illness caused by Enterohaemorrhagic Escherichia coli (EHEC) claimed at least 50 lives during one of the largest outbreaks in 2011. EHEC have been encountered in leafy vegetables, sprouted seeds, raw milk and cheeses, as well as fresh, minced, and mixed meat preparations. Most infections have been with E. coli O157. However, there are various other strains of non-O157 E. coli capable of causing sickness and death that should be examined in food. Screening for pathogenic E. coli has been recommended using the virulence factors stx1, stx2, and the eae gene. Serotype E. coli O104:H4, the cause of this severe outbreak in 2011, could have been detected if such screening had been in place.

Purpose: Used during the outbreak of 2011 by German government laboratories, BIOTECON Diagnostics developed the foodproof EHEC Screening Kit to determine whether EHEC are present in a food sample in less than 24 hours.

Methods: This real-time PCR method is performed by separately detecting Shiga toxins stx1 and stx2 as well as the intimin eae gene in one simultaneous assay.

Results: Unlike the current ISO method, all known variations of the pathogenicity genes stx1, stx2, and eae can be detected with the foodproof EHEC Screening Kit, including stx2f. Following one enrichment, each kit achieves a sensitivity of detecting one cell in a food sample. Similar to other foodproof real-time PCR detection kits, BIOTECON Diagnostics has included additional controls to prevent false-positives and false-negatives. These kits are compatible with nearly all open real-time PCR instruments.

Significance: The foodproof EHEC Screening Kit can be used in conjunction with the foodproof E. coli O157 Detection Kit as well as the foodproof E. coli O104 Detection Kit to specifically identify these serotypes.