Food Pathogen Testing
A presumptive-positive screening result in food safety testing is not automatically treated as a final confirmed positive. At Biotrax, presumptive-positive samples in microbiological testing undergo additional cultural confirmation. This may include streaking the enriched sample onto appropriate selective or differential agar, incubating the plates, evaluating characteristic colony growth, and performing further identification steps required by the pathogen detection method. For example, a presumptive pathogenic E. coli result may be plated onto a suitable MacConkey-based selective or differential medium and incubated so characteristic colonies can be evaluated before further confirmation. The exact agar, incubation conditions, and identification steps vary by organism, product matrix, and method. Salmonella, Listeria, and pathogenic E. coli each require organism-specific confirmation procedures. Confirmatory culture extends the final turnaround time but helps distinguish an initial presumptive screen in food safety testing from a confirmed laboratory finding. FDA guidance similarly treats rapid-method positives as presumptive and requires confirmation using established cultural procedures. Remember, a presumptive positive does not mean confirmed positive; a rapid screen identifies a sample that requires further evaluation, with the final result issued after the applicable confirmation process is completed.
PATHOGENS WE TEST FOR
SALMONELLA SPECIES
Salmonella is a group of foodborne bacteria linked to a variety of ingredients and finished products, making it a critical focus for food safety testing and microbiological testing.
Why test for it: Conducting tests for Salmonella can support supplier verification, enhance raw-material programs, ensure the integrity of finished-product release, meet customer specifications, verify food safety, or aid in an investigation regarding a suspected hazard involving pathogen detection.
Available analytical portions: Depending on the product, specification, sampling plan, and program requirements, options for analysis include 25-gram and 375-gram portions.
LISTERIA SPECIES
Listeria species testing is a crucial part of food safety testing, as it detects members of the broader Listeria genus, not just L. monocytogenes.
Why test for it:
The presence of any Listeria species can provide valuable insights into hygiene conditions or environments that may also support L. monocytogenes. This type of microbiological testing may be requested as part of a comprehensive monitoring, verification, or investigation program for pathogen detection.
Available analytical portions:
Options of 25-gram and 125-gram samples are available where appropriate.
Important Distinction:
A result indicating the presence of a Listeria species is not equivalent to a confirmed result for Listeria monocytogenes. It's essential that the selected analysis aligns with the specific organism the client needs to evaluate.
LISTERIA MONOCYTOGENES
Listeria monocytogenes is the disease-causing species associated with listeriosis and poses a significant threat to food safety testing, particularly concerning ready-to-eat foods as it can survive and grow under refrigerated conditions.
Why test for it:
Testing for this pathogen is crucial as it may support finished-product safety verification, hold-and-release programs, investigations, customer requirements, and follow-up activities when the organism is identified as a relevant hazard through microbiological testing.
Available analytical portions:
25-gram and 125-gram options are provided based on the pathogen detection testing plan or specification.
E. COLI (including O157:H7)
E. coli O157:H7 is a pathogenic strain capable of producing Shiga toxin, leading to severe foodborne illness.
Why test for it: Testing is crucial for food safety testing as it helps verify foods and ingredients where O157:H7 is a recognized hazard, including certain raw meat products, produce, and other susceptible matrices. This forms an essential part of microbiological testing and pathogen detection protocols.
Available analytical portions: Depending on the specification, program, and sample type, 25-gram and 375-gram options are available.
Important distinction: It's essential to differentiate this testing from generic E. coli enumeration, which is commonly used as a hygiene or process indicator.
PCR STEC SCREENING
Shiga toxin-producing E. coli, or STEC, includes pathogenic strains that carry genetic markers associated with Shiga toxin production, making it a critical focus in food safety testing.
Why test for it:
PCR screening may be utilized when a product, ingredient, customer requirement, or risk-based program necessitates evaluation beyond a general E. coli count, enhancing the effectiveness of microbiological testing.
Given that STEC programs can vary in their genetic targets, serogroups, analytical portions, and confirmation requirements, it’s essential to confirm the specific screening scope with Biotrax before submitting samples for pathogen detection.
SAMPLE PORTIONS
WHAT DO 25 G, 125 G, AND 375 G MEAN?
The analytical portion in food safety testing refers to the amount of sample prepared and tested for pathogen detection. A larger analytical portion provides broader sample coverage in microbiological testing, but it does not guarantee that the entire production lot is free from the organism. The appropriate portion may be determined by factors such as:
- The product and identified hazard
- A customer or supplier specification
- Regulatory or industry guidance
- The sampling plan
- Lot size and production process
- The intended use of the result
- The laboratory method
Clients should not assume that a larger portion is automatically required or more appropriate for food safety testing. Our team can assist in confirming which option best fits the testing request.
