Case study: Dip manufacturer reduces Listeria positive rates to under 0.5% using Listeria Right Now

April 11, 2018

Listeria, as one of the most dangerous foodborne pathogens, poses a risk to consumer health as well as a company’s brand. It’s one of the most persistent food safety concerns faced by the food manufacturing industry today. Because of the lethality of this pathogen, many companies hold product until traditional lab tests determine the product is Listeria-free. Holding product shortens shelf-life, degrades quality and costs money.

To address these issues, Neogen has developed a one-hour sample-to-result test for environmental Listeria that requires no enrichment. It’s fast, easy, and effective — and no enrichment means that pathogens are not amplified at the food production facility. Companies can have results within one hour of taking a sample. It’s effectiveness is the reason the test is a 2018 CFIA Innovation Award Winner.

With Listeria Right Now, swabs are placed in a lysis buffer that breaks up the bacteria, releasing its ribosomal RNA (rRNA). If Listeria is present, after converting the rRNA to DNA through a reverse-transcription reaction, the test’s reagents amplify copies of the DNA, which is read by a fluorescent reader indicating a positive or negative — all within an hour of taking the sample.

One company that has adopted Listeria Right Now is a United States-based producer of dips and salsas. After dealing with Listeria positives, the company achieved improvement beyond expectations after implementing Listeria Right Now. The company reduced its testing turnaround time from 48–72 hours to one hour, can now run approximately 200 tests per week, and has reduced Listeria positive results to under 0.5%.

The benefits were so impressive that representatives from the state department of agriculture visited one of the company’s plants to see how they made such dramatic improvements in Listeria prevalence.

“They came to see how we managed to get our environmental rates so low,” said the company’s senior director of food safety. “They were quite surprised!”

Faster results

The senior director had one answer for the biggest benefit provided by Listeria Right Now: “Time. Time to run, and time to re-clean, if necessary, and get machines up and running.”

Machine downtime after positive Listeria results, sometimes lasting days, had been a major frustration to him and his team. With Listeria Right Now, post-cleaning test results became available in less than a day, enabling the company to do Zone 1 testing.

“Previously, we’d take a swab and send it out with a long turnaround time. By the time we’d get the results back, it’s about two days before we can do anything about a positive,” he said. “Now we can get them back in 60 minutes.”

With fast results, not only does production resume sooner, but the actual process of finding Listeria growth niches becomes quicker and more efficient. The company now runs about 200 Listeria tests a week, and has run as many as 100 in a single day.

“Hunting down Listeria was of utmost importance,” he stated. “We swabbed all over, trying to understand where it was and how it was spreading. We were swabbing people’s boots, just trying to find out how it had been tracked around. With Listeria Right Now, we could take immediate corrective actions.”

Fewer positive test results

With earlier methods, the company had lowered its rate of positive results to about 3%. With Listeria Right Now, its food safety team was able to initiate a seek-and-destroy Listeria hunt, reducing that rate to just 0.5%.

With the flexibility provided by the new system’s quickness, the company made the following changes:

    • Rerouted traffic patterns for product and personnel, based on where Listeria was found to have been tracked.
    • Uncovered previously unknown harborage sites, thanks in part to the small-sized Listeria Right Now swab’s ability to reach hard-to-get areas.
    • Refined cleaning practices and instituted twice-daily cleaning for newly found harborage sites.
    • Replaced rubber feet, which had been identified as harborage sites, with stainless steel on some pieces of equipment.

Practical benefits

Cutting turnaround times and reducing positive rates were the main concerns for the company, and Listeria Right Now’s rapid time-to-result was the main factor in attaining those goals. But the testing system offered a few other pluses that helped in unexpected ways.

The system’s small-sized swabs could reach areas that sponges from other tests couldn’t. Small holes, cable bundles and spaces under equipment feet were areas that were previously unable to be tested, because the sponges traditionally used with other Listeria environmental testing methods simply couldn’t reach them. Equipment feet were even identified as harborage areas for Listeria after the new system was implemented.

“We used a sponge to swab a piece of equipment that came back negative,” the senior director said, “but when we went at it again with one of Neogen’s swabs, it was positive.”

The company also uses a lot of powder antimicrobial products, which tend to wound cells, making them inviable without killing them. Listeria cells would recover after the powder was removed, and previous testing methods didn’t identify this issue. “Now, with the Listeria Right Now, we don’t care whether a cell is viable,” he said. “We can get rid of it regardless.”

Onward and upward

Listeria poses an enormous threat to food manufacturers for many reasons: equipment downtime, potential for recalls, risk to consumer safety and brand trust, and so on. Listeria Right Now has been shown to reduce these risks, as demonstrated in this case study, by drastically shortening turnaround time and cutting positive result rates to lower percentages than what can be attained with other testing methods. The test’s rRNA-replicating technology eliminates the need to grow cultures on-site, making it a viable option for companies looking to bring Listeria environmental testing in-house.


Category: Food Safety, Dietary Supplements, Food & Beverage, Pharmaceutical & Biotech, Pathogens, Environmental Monitoring