The Dupont BAX® System method for the detection of Salmonella in foods and environmental surface samples
Background: This is a qualitative highly specific analysis, and this test will detect if only one Salmonella spp. cell is present, therefore resulting in a negative or positive result. This assay does not tell you how much of the pathogen is present.
Standard sample sizes are one swab, or 25g of food. Representative sample portions are collected from sample submitted, mixed with highly selective enrichment media and incubated for 12 to 26 hours (depending on sample size and matrix). After incubation, cells from the sample enrichment are broken open (lysis) to expose their DNA, which, if the target Salmonella DNA is present, will be copied thousands of times (amplification), allowing for detection via the BAX-PCR Salmonella spp. assay.
The BAX System uses DNA-based technology to provide results within 48hrs that are reliable and reproducible, allowing food producers and processors to quickly and accurately release safe products to the market. If the test is positive for Salmonella, confirmation is required using a traditional quantitative culture method (MFHPB-20).
Method: Health Canada (MFLP-29)
Turn Around time: 2-3 Business Days
Reported results: Negative or Positive
SPECIMEN REQUIREMENTS
Container/Kit: Submit 250 grams of food in a sterile plastic sample bag with round wire closure or swab.
Collection information: See Section Sampling under Food Sampling.
Requisition: Complete all fields of the form. See section Forms under Microbiology Sample Sheet.
Sterile Bag: See section Form under Requisition for Containers and Supplies.
Limitation:None.
Preparation prior to transport: Keep refrigerated or frozen.
Shipping Instructions:
- Ship all foods in containers with hard walls and lids secured in the closed position.
- Shipping containers must be labelled with the submitting organization, unique identifier and contents e.g. FOOD SAMPLES on the outside of the container.
- Shipping containers used for food samples should be dedicated to food samples and not be used for other types of environmental samples.
- Ship frozen foods in an insulated container with sufficient dry packs to maintain the frozen state.
- Ship perishable foods in an insulated container with sufficient cold packs to maintain a temperature as close to 4°C as possible. If ice is used, contain the ice in a manner that does not allow water contact with the samples.
- Submit all food samples to the laboratory as soon as possible.
TEST INFORMATION
The presence of Salmonella spp. in food is screened by real time polymerase chain reaction (RT-PCR). All RT- PCR positive samples will be confirmed by culture techniques including nonselective pre-enrichment, selective enrichment followed by isolation on selective agar plates, biochemical and serological identification. Salmonella spp. should be absent from ready-to-eat foods.Interpretation Guide for Salmonella results
Interpretation of results
The RT-PCR results will be reported as Not Detected, Detected or Indeterminate for Salmonella species. Routine culture will be set up for all detected and indeterminate RT-PCR results. Culture of all RT-PCR positive samples will be reported as Not Detected or Refer to Confirmation Test. A final serotype will be identified and reported for all Salmonella culture positive food samples.