Modification and Matrix Extension of the Bio-Rad iQ-Check E. coli O157:H7, STEC VirX, and STEC SerO Test Kits for the Detection of Shiga Toxin-Producing Escherichia coli (STEC) and Escherichia coli O157 From a Single Enrichment.

BACKGROUND: The iQ-Check Real-Time PCR kits use PCR technology based on gene amplification and detection by a real-time PCR thermalcycler for the detection of target analytes in select food matrices. The iQ-Check E. coli O157:H7 [Performance Tested MethodSM (PTM) 020801] and STEC VirX and STEC SerO (combined PTM 121203) methods were previously validated for different matrices under different enrichment schemes. OBJECTIVE: To modify the current iQ-Check E. coli O157:H7 Kit for the detection of Escherichia coli O157:H7 from 25 to 375 g for raw ground beef (17% fat), raw beef trim, and fresh spinach. In addition, a matrix extension was validated for iQ-Check E. coli O157:H7 for raw chicken breast without skin (25 g), raw chicken thigh with skin (25 g), mechanically separated chicken (25 g), and raw ground pork (25 g). The study also included the modification of the iQ-Check STEC VirX and SerO Kits for the detection of non-O157 Shiga toxin-producing E. coli (STEC) for raw ground beef (375 g), raw beef trim (375 g), and fresh spinach (375 g) from STEC Enrichment Broth to buffered peptone water (BPW). All tests were carried out at 8-22 h (10-22 h for fresh spinach). METHODS: Ground beef, beef trim, and spinach were co-inoculated with E. coli O157:H7, non-O157 STECs, and Salmonella spp. and analyzed for E. coli O157:H7 and non-O157 STECs after an 8-22 h enrichment in BPW for the beef matrices and after a 10-22 h enrichment in BPW for spinach. The chicken matrices were inoculated with E. coli O157:H7 only and analyzed after an 8-22 h enrichment in BPW. The iQ-Check Free DNA Removal Solution workflow was utilized for all matrices. Confirmations at the 22 h time point and method comparisons were conducted with the appropriate reference method as outlined in the U.S. Food and Drug Administration Bacteriological Analytical Manual Chapter 4A or the U.S. Department of Agriculture Food Safety and Inspection Service Microbiology Laboratory Guidebook Chapters 5.09 and 5B.05. For the iQ-Check STEC VirX and STEC SerO Kits, inclusivity and exclusivity were also performed. RESULTS: The two inclusivity and exclusivity evaluations indicated that the test methods can accurately detect the target analytes and correctly excluded nontarget organisms after 8 h of enrichment. In the method comparison study, the iQ-Check E. coli O157:H7 and STEC VirX and STEC SerO test kits demonstrated no statistically significant differences between candidate and reference method results or between presumptive and confirmed results for all food matrices analyzed and the two time points (8 or 10 and 22 h). Both time points produced the same results, with no discrepancies. CONCLUSIONS: The iQ-Check real-time PCR kits are effective methods for the detection of E. coli O157 and non-O157 STECs (both the virulence factors and the O groups) from raw ground beef, raw beef trim, and fresh spinach in 375 g samples enriched in BPW for 8-22 h (10-22 h for fresh spinach). In addition, the iQ-Check E. coli O157 Kit is effective in detecting E. coli O157 in 25 g samples of raw chicken breast without skin, raw chicken thigh with skin, mechanically separated chicken, and raw ground pork. The iQ-Check test kits allow the end user to pair enrichments for multiple target analytes, allowing the user to prepare a single enrichment and perform a single DNA extraction. The Free DNA Removal Solution removes free DNA from samples prior to PCR analysis, protecting DNA from intact and living cells. HIGHLIGHTS: The method modifications were granted based on the data collected.

Modification of the Bio-Rad iQ-Check Listeria spp. Kit for the Detection of Listeria Species in Environmental Surfaces.

BACKGROUND: The Bio-Rad iQ-Check Listeria spp. Kit uses real-time PCR technology for detection of Listeria species in select food matrixes and environmental surfaces. OBJECTIVE: The iQ-Check Listeria spp. method was modified to reduce the enrichment medium volume for environmental sponges from 225 and 100 to 60 mL and to reduce the enrichment time for sponges and swabs from 25 ± 1 to as short as 18 h. The modified method was validated with stainless steel, polystyrene plastic, and sealed concrete using sponges or swabs with two different neutralizing buffers (Letheen Broth and HiCap™ Neutralizing Broth). In addition, the Bio-Rad Free DNA Removal Solution was used for all environmental samples. METHODS: The iQ-Check Listeria spp. modified method was compared with the reference culture method in the U.S. Department of Agriculture Food Safety and Inspection Service Microbiology Laboratory Guidebook Chapter 8.10 using an unpaired study design. RESULTS: In the method comparison study, the iQ-Check Listeria spp. modified method demonstrated no statistical difference in performance between candidate and reference method results or between presumptive and confirmed results for all environmental surfaces analyzed using HiCap Neutralizing Broth (World Bioproducts LLC) and Letheen broth. CONCLUSIONS: The modified iQ-Check Listeria spp. method is an effective method for the detection of Listeria species in environmental surfaces using both types of neutralizing buffer. HIGHLIGHTS: The method modification was granted based on the data collected.

Evaluation of the iQ-Check®Salmonella II Assay in Select Foods: Collaborative Study, First Action 2017.06.

The iQ-Check Salmonella II Real-Time PCR test kit utilizes Salmonella-specific oligonucleotide probes and primers for the rapid and specific detection of Salmonella species in select food types. The alternative method was evaluated by using 375 g test portions in an unpaired study design for two matrices, milk chocolate and dry dog food. Each matrix was compared with the U.S. Food and Drug Administration Chapter 5 Salmonella reference method. Fourteen technicians from 12 laboratories, including academia and industry, located within the United States and Canada participated in the collaborative study. Three levels of contamination were evaluated for each matrix: an uninoculated control level (0 CFU/test portion), a low inoculum level (0.2-2 CFU/test portion), and a high inoculum level (2-5 CFU/test portion). The statistical analysis was conducted according to the Probability of Detection (POD) statistical model. The results obtained for the low inoculum level test portions produced a difference in the candidate presumptive and confirmatory results (dLPOD) value with a 95% confidence interval of -0.05, (-0.15, 0.06) for the milk chocolate and 0.10, (-0.01, 0.21) for the dry dog food. The dLPOD results indicate an equivalence between the candidate method and reference method for the matrices evaluated, and the method demonstrated acceptable interlaboratory reproducibility as determined in the collaborative evaluation. False positive and false negative rates were determined for each matrix and produce values of <2%. Based on the data generated, the method demonstrated acceptable interlaboratory reproducibility data and statistical analysis.

iQ-Check Salmonella II: real-time polymerase chain reaction test kit. Performance Tested Method 010803.

iQ-Check Salmonella II is a real-time PCR kit for detection of Salmonella in foods. Specific oligonucleotide probes are used to detect target DNA during the amplification, by hybridizing to the amplicons. These probes are linked to a fluorophore, which fluoresces only when hybridized to the target sequence. As part of an Emergency Response Validation due to a massive outbreak and subsequent recall, peanut butter was tested to compare the performance of iQ-Check Salmonella II to the U.S. Food and Drug Administration's Bacteriological Analytical Manual (FDA-BAM) reference method for detection of Salmonella. A single enrichment in buffered peptone water was used for a reduced enrichment time of 21 +/- 1 h over the 48 h reference method. There was no significant difference in the performance of the iQ-Check kit when compared to the FDA-BAM method, as determined by Chi-square analysis. All samples identified as positive by iQ-Check were confirmed by reference method protocol.