Research Update - Final

Category: Methodology Improvements Project Title: Comparison of non‐O157 Shiga Toxin‐producing E. coli Detection Systems Mick Bosilevac, USDA, ARS, US Meat Animal Research Center Objective: To identify strengths and weaknesses of Shiga toxin‐producing E coli detection systems and kits in a side by side fashion Three commercial Shiga toxin‐producing E. coli (STEC) detection tests and two third‐party laboratories were compared to the MLG (5B) and USMARC molecular methods for ability to detect top‐6 STEC (aka enterohemorrhagic E. coli [EHEC]).  FSIS MLG 5B STEC Detection  DuPont Qualicon BAX® System STEC Suite – commercial detection test  BioControl Systems Assurance GDS Top STEC – commercial detection test  Pall GeneDisc System for non‐O157 STEC – commercial detection test  IEH Laboratories – third‐party lab  Neogen NeoSEEK – third‐party lab  US Meat Animal Research Center STEC detection and isolation protocols The study design was a three‐part evaluation in two phases: • Two inoculation studies • Each method/system used according to its protocol (medias, incubation temperatures & times, material). • Each method/system used to test the same TSB enrichments (ground beef varying weight/volume/time). • One set of “Real World” samples • Each method/system used on 500 enrichments from a regional service lab. The results indicated all methods, used as directed, can detect low levels of inoculated top‐6 EHEC though results varied among methods (Table 1). One hundred sixty of 500 samples were found to be potential positive by one or more methods, but only 2 samples were positive by all methods. This information allows users of STEC detection tests to draw comparisons and critically consider the value of a potential positive when multiple organisms may be present. The results also provide a baseline of what number of potential positives different methods may give.