The purpose of this study was to evaluate the QUALIBAXTM 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.
Effects of storage temperature (5, 10, and 25℃) on the survival and growth of Cronobacter sakazakii ATCC 29544 in prepared powdered infant foods (PIF); “vegetable and rice porridge” (VRP), “mixed vegetable and wheat paste” (MVWP), “liver, vegetable, and wheat paste” (LVWP) and “apple juice” (AJ) were investigated. C. sakazakii showed grown in VRP, MVWP, and LVWP at 25℃, but no growth at 5 or 10℃. In AJ, C. sakazakii was inactivated at 25℃ for 24 hr, and there was no growth or slight decrease was observed at 5 and 10℃. These results indicate that, similarly to other PIFs, bacterial growth in the tested PIFs increase with storage under room temperature. However, it was suppressed by the tested AJ, and also a rapid decrease was found at 25℃.