Sample that: Dietz & Watson takes up Listeria tech

By Joseph James Whitworth

- Last updated on GMT

It is only currently available for Listeria on environmental samples but more assays are in development
It is only currently available for Listeria on environmental samples but more assays are in development

Related tags Microbiology

Dietz & Watson has cut time to result by days by using Sample6 technology to test, find and remediate Listeria before products leave one of its plants.

Detect/L is an enrichment-free, single-shift pathogen diagnostic test for Listeria species. 

Dietz & Watson previously used PCR and sent swabs to third-party labs for testing.

The firm, which prepares deli meats and artisan cheeses, now tests all of its environmental Listeria samples onsite every week.

Based on use at the Philadelphia plant, it plans to take up Sample6 at all plants before the end of year.

Listeria target

Bob Seaver, Dietz & Watson director of quality control, said he saw the technology in an advert and the firms have been working together since August.

“I am always interested in new technology and anything for Listeria that provides faster results,” ​he told

“We take samples in the morning, the second shift comes in and the results are complete before my clean- up crew starts work.

“You always need to continuously improve as you don’t know what is around the corner.​   

“It is cheaper than sending to an outside lab, who if there was a presumptive positive, could charge to confirm. Now I assume a presumptive is a positive but in the extra time for confirmation we can work through.”

AOAC approval

Sample6’s DetectL system received AOAC approval in April​ for Listeria species on environmental surfaces and is part of the Bioillumination Platform with Sample6 Control which is the software element.

Surfaces are swabbed with a sponge, the Sample6 buffer solution is added, it is incubated and then centrifuged before being put in the detection system and lighting up if Listeria is present.

It does this through biosensors that have been designed to target the pathogen and make the sample light up if bacteria are there.

Sample6 is a four year old firm and after two or three years of R&D the AOAC certification allowed market launch.

Tim Curran, CEO of the company, told us it can provide a result in about seven hours.

“The first thing to note is that changing methods is a serious business, you don’t just change like that, it has to be a thoughtful and step by step process,” ​he said.

“Our process takes about 30 minutes of sample preparation, six hours incubation and 30 minutes to do reading so can be done in a single work shift.

“The assay in the process kills bacteria in the sample, where enrichment involves growing the pathogen near food production.”

Before product leaves plant

Carla Mulhern, a Dietz & Watson microbiologist, said the firm still sends out for Salmonella tests and results at customer requests but the system allows product to be tested before it goes to market and removed from the factory.

“The analysis is easy with the number of steps and there is no cross contamination risk,” ​she said.

I was able to train my staff in just a few days, and none of us miss the complexity of the previous testing methods.

“It allows us to be in a good place with the USDA inspector to verify we are clear of Listeria as we are able to be on site and work with them.”

Curran said while the test is only for Listeria on environmental surfaces they are working on other pathogens and food matrixes.

“We are working with eight companies on this and in development we are going to Salmonella, E.coli and then Campylobacter, I would expect to see some of these be available from next year,” ​he said.

“There are three dimensions for the future, we have Listeria in the environment so we are looking at other bugs to prove it works on any matrixes.

“The initial focus is on dairy and produce and we will then work through 15 or 20 food matrixes.

“We are US-focussed to start but we will then move outside and look at international expansion and a further reaching platform is to extend outside of food to other industries.”  

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