5 more questions about Listeria Right Now™

May 16, 2018

Previously we’ve covered the questions we get about the technology behind Listeria Right Now™, our one-hour-long environmental Listeria test that features molecular-level accuracy with no need for enrichment.

In the time since, we’ve talked to more of our customers, and heard more about how they use Listeria Right Now and what kinds of things they wonder about the test system. Here are some more questions, and more importantly, some more answers.

Can I use this test on Zone 1 product surfaces during operational runs for USDA-regulated products?

Listeria Right Now is designed for post-cleaning, pre-production environmental use. This includes all zones. It hasn’t been validated against product matrices at this time, though we’re working on a few currently.

How exactly are you able to detect 4 CFU per swab without enrichment?

Listeria Right Now targets ribosomal RNA (rRNA). This creates a significant advantage — there are typically 1,000 to 10,000 copies of rRNA, compared to only one copy of DNA, which traditional polymerase chain reaction (PCR) systems target. Hence, with rRNA as a target, there can be a 1,000- to 10,000-fold increase in target analyte concentration.

In addition, the reaction within the reagent tubes is isothermal, meaning the molecular replication happens at a constant rate, compared to the thermal cycling replication that happens with PCR systems. To sum it up, when you start with a greater number of targets and faster replication, you get a faster result.

You mentioned that Listeria Right Now targets rRNA, but the replication occurs on DNA strands. How does this happen?

The reaction includes a reverse-transcription step that converts rRNA to DNA prior to replication.

How does the ANSR system read the reaction occurring in the reader?

The ANSR reader measures fluorescent light using optics within the device. As the isothermal reaction takes place, a fluorescent beacon is released when it binds to the target analyte’s DNA strand. As more target DNA replicates are produced, more beacons are released, resulting in more fluorescence. The ANSR reader tracks the light output from the sample and compares it to the output from the positive control, allowing it to determine if the sample is negative or positive.

Does Listeria Right Now have AOAC approval?

AOAC approval is pending.

Got more questions? Get in touch via our website, or check there to see if your question is covered in our expanded Frequently Asked Questions.

Category: Food Safety, Food & Beverage, Pathogens