AOAC PTM approval for 3M's Listeria monocytogenes assay

The approval certifies that the test kit is considered equivalent or better than standard reference methods for select food matrices.

The assay, introduced in July 2013, provides results in 24 hours of enrichment – days faster than the standard methods.

John David, global marketing director for 3M Food Safety, said that method validations are important to ensure a test is accurate, reliable, reproducible, and can meet specific performance claims.

“Our customers rely on these validations, which enable them to meet their internal requirements and also give increased confidence in the quality of their results,” ​he told FoodQualityNews.com.

Fast recovery and high sensitivity​

David said the assays consist of two parts: optimal growth conditions that enable fast recovery of microorganisms and rapid, high-sensitivity molecular detection.

“This allows us to deliver methods with a fast total time to result, for a range of pathogens.  For example, our 3M Molecular Detection Salmonella assay can detect Salmonella in raw ground beef and raw ground chicken after 10 hours of enrichment, which is of great benefit to producers of these highly perishable products," ​he said.

“​The 3M Molecular Detection System has been adopted by variety of customers, including food processors, contract testing labs, government, and universities, across all regions of the world. ​

“The system is being used to test a wide range of sample types, including meat, poultry, produce, dairy, seafood, processed foods, and environmental samples.”​

Select food samples analyzed during the validation study include full fat cottage cheese, chocolate milk, beef hot dogs, cold smoked salmon, bagged raw spinach and whole cantaloupe.

Testing also covered environmental surfaces including stainless steel and concrete.

3M Molecular Detection System use loop-mediated isothermal amplification to amplify target pathogen DNA combined with bioluminescence to detect the amplification.

Presumptive positive results are reported in real-time while negative results are displayed after the run is completed.

Each 3M Molecular Detection Assay uses multiple primers to recognize regions of the target pathogen’s genome and Bst DNA polymerase to provide amplification of DNA.

Listeria species matrix extension​

In a separate development, the 3M Molecular Detection Assay Listeria species has received a matrix extension by the AOAC Performance Tested Methods program.

The test kit received the PTM extension for full fat cottage cheese, beef hot dogs, deli turkey, cold cooked salmon, bagged raw spinach, whole cantaloupe, and environmental surfaces including stainless steel and concrete.

To achieve this an application is completed, two protocols are written for internal validation and independent lab study, a final written report from these studies is submitted to review to the AOAC and a positive outcome means the certificate is granted.

David said the firm is now looking to achieve AOAC Official Method of Analysis (OMA) as most regulators require methods that have been collaboratively studied to demonstrate it can be consistently performed by many labs and compares well to the reference method.

The process requires an application to AOAC with at least one matrix to be studied, a written approved protocol, a lab certified and experience in organizing and doing a collaborative study, 10 or more labs willing to participate in the study and the final manuscript of the study with reference to AOAC PTM is submitted for review – a positive outcomes means AOAC OMA is granted.