ABSTRACT
The automated method for enumeration of Escherichia coli, TEMPO EC, in foods uses a dehydrated culture medium and enumeration card containing 48 wells across three different dilutions for the automatic determination of the most probable number (MPN). The alternative method was compared in a multilaboratory collaborative study to AOAC Official Method 966.24. Six food types were artificially contaminated with E. coli: raw ground beef, bagged lettuce, cooked chicken, pasteurized crabmeat, frozen green beans, and pasteurized whole milk. All foods were analyzed for E. coli counts by 11 collaborating laboratories throughout the United States. Test portions from the six food types each contaminated at four different contamination levels were evaluated. The study demonstrated that the TEMPO EC method is a reliable, automated assay for the enumeration of E. coli in foods.
Subject(s)
Colony Count, Microbial/methods , Escherichia coli/metabolism , Food Contamination , Food Microbiology , Animals , Automation , Cattle , Chickens/microbiology , Food Analysis , Laboratories/standards , Meat/microbiology , Reproducibility of Results , Research Design , Seafood/microbiology , Vegetables/microbiologyABSTRACT
QIAGEN mericon Escherichia coli O157 Screen Plus and mericon E. coli Shiga toxin-producing E. coli (STEC) O-Type Pathogen Detection Assays use Real-Time PCR technology for the rapid, accurate detection of E. coli O157 and the "big six" (O26, O45, O103, O111, O121, O145) (non-O157 STEC) in select food types. Using a paired study design, the assays were compared with the U.S. Department of Agriculture, Food Safety Inspection Service Microbiology Laboratory Guidebook Chapter 5.09 reference method for the detection of E. coli O157:H7 in raw ground beef. Both mericon assays were evaluated using the manual and an automated DNA extraction method. Thirteen technicians from five laboratories located within the continental United States participated in the collaborative study. Three levels of contamination were evaluated. Statistical analysis was conducted according to the probability of detection (POD) statistical model. Results obtained for the low-inoculum level test portions produced a difference between laboratories POD (dLPOD) value with a 95% confidence interval of 0.00 (-0.12, 0.12) for the mericon E. coli O157 Screen Plus with manual and automated extraction and mericon E. coli STEC O-Type with manual extraction and -0.01 (-0.13, 0.10) for the mericon E. coli STEC O-Type with automated extraction. The dLPOD results indicate equivalence between the candidate methods and the reference method.