Studies on a Rapid Method for Detecting Shiga Toxin-Producing Escherichia coli (STEC) in Food Using the QUALIBAX^TM Q7 System

Abstract

The purpose of this study was to evaluate the QUALIBAX^TM Q7 System (BAX system) for detecting non-O157 Shiga toxin-producing Escherichia coli (STEC) serogroups (O26, O103, O111, O121, O145) and STEC O157. The BAX system real-time PCR assay STEC suite was evaluated, including a screening assay for the stx and two panel assays to identify the target serogroups. For STEC O157, BAX system real-time PCR assay E. coli O157 : H7 was used. The BAX system assay was found to detect STEC O26, O103, O111, O121, O145 and O157 in pure culture. Each assay was 100% inclusive for the STEC strains used. And no cross-reactivity was observed. Sensitivity of a screening assay for the stx was ≧1.8×10³ CFU/ml in cultures of ground beef or lettuce. E. coli O157 : H7 was detected at a level of ≧1.8×10⁴ CFU/ml. On a collaborative study, the performance of the BAX system assay was compared with that of a culture method for detection of STEC O26, O111 and O157 in ground beef and lettuce. Sensitivity of the BAX system method was better than a culture method. These results suggest that the BAX system can be used as a rapid method for detecting STEC in food samples.