Evaluation of the Alere SHIGA TOXIN QUIK CHEK™ in comparison to multiplex Shiga toxin PCR

• All Stx subtypes except Stx2f were detected with the SHIGA TOXIN QUIK CHEK.
• Specificity was 100% for all test methods.
• Sensitivity of direct fecal testing was unacceptably low (46.7%).
• Culture or enrichment of the stool should always be performed before testing.

Shiga toxin-producing Escherichia coli (STEC) causes gastrointestinal outbreaks worldwide and due to its low infectious dose highly sensitive diagnostics are needed. In this study, the performance of the enzyme immunoassay SHIGA TOXIN QUIK CHEK (STQC) (Alere, TechLab) for the detection of Stx1 and Stx2 was evaluated directly from fecal samples, from culture on agar (SMAC(−CT)) and from broth enrichment (mTSB) in comparison to our in-house multiplex PCR. The STQC could not detect the Stx2f subtype, but detected all other subtypes with an analytical sensitivity varying between 108 and 104 CFU/ml. The SMAC(−CT) assay had the best performance with an overall sensitivity of 93.3%; broth and direct fecal testing had sensitivities of 74.1% and only 46.7%, respectively. All methods were 100% specific. Because of the unacceptably low sensitivity we do not recommend applying the STQC directly on stools, but only after overnight culture.