DuPont L. mono assay gains AOAC PTM approval

The BAX system real-time PCR Assay test has been validated on sample matrices, including frankfurters, cooked shrimp, spinach, queso fresco and environmental surfaces.

DuPont’s assay for Listeria was certified in August last year​ after launch earlier in 2014​.

Customer needs and preferences​

Shannon Bullard, diagnostics global product manager for DuPont Nutrition & Health, said most customers will test for Listeria species (as an indicator for the presence of L. monocytogenes) or specifically for L. monocytogenes.

“The testing option depends on each customer’s products and preferences,” ​she told FoodQualityNews.

“The key message is that both options – the BAX System Real-Time PCR Assay for Genus Listeria and the BAX System Real-Time PCR Assay for L. monocytogenes – are externally validated by the AOAC Research Institute for testing food and environmental samples with a variety of enrichment options to best meet the needs of a variety of testing needs.”​

Certification includes a combined testing method from environmental samples developed by DuPont Nutrition & Health and FoodChek Systems, based in Canada.  

The method includes a 20-hour, single-stage enrichment in FoodChek’s Actero Listeria Enrichment Media followed by processing with the DuPont BAX System.

It allows for detection of L. monocytogenes from environmental samples in about 22 hours.

Additional validation studies are in progress to certify the method using the Actero Listeria Enrichment Media, which will reduce enrichment times further, said DuPont Nutrition & Health.

The system is certified in frankfurters for 28-48 hours in proprietary 24 LEB Complete or 41-50 hours in reference method media (2-part enrichment), spinach and shrimp – 24-48 hours in proprietary 24 LEB Complete or 48-52 hours in reference method media and queso fresco - 26-48 hours in proprietary 24 LEB Complete or 48-52 hours in reference method media.

Assurance of accurate method​

Bullard said customers who have been using this BAX system assay since its commercialization will not need to change methods.  

“​We have found that AOAC and other third-party validations make it easier for customers to adopt a new method, as they now have the assurance that the method is accurate, robust and reliable without having to perform large internal studies within their laboratory to test the method before adoption.”​

DuPont Nutrition & Health does not have validation studies in progress for OMA validation but it said ‘based on the voice of the market’ it may pursue it in the future.

William J. Hogan, president and CEO of FoodChek, said the test can result in superior production work flow, additional product shelf life and an improved financial bottom line.

“This 22-hour combined Listeria test developed by DuPont Nutrition & Health and FoodChek provides increased value to testing laboratories and food processors alike​.” 

Additional validation studies have been submitted to AOAC-RI for detecting L. monocytogenes in a variety of foods using Actero Listeria Enrichment Media. 

It is also working towards validation for the BAX System real-time genus Listeria assay for testing food and environmental samples with this media.