Sample6 DETECT: Can you make it faster?
At Sample6, our mission is to provide food producers with a fast and reliable assay for pathogen detection. The Sample6 DETECT/L assay requires only a six-hour incubation, making it the first AOAC-certified, enrichment-free assay that can be performed start to finish in a single shift. However, this is just the first step. Under ideal conditions, with healthy cells, we are able to detect a single cell in one hour, but real world conditions present real challenges. Let’s walk through those challenges and talk a bit about what we are doing to address them:
Top 3 Challenges
Listeria! Listeria! Where are you?
Picture a crowded marketplace, filled with hundreds of thousands of people. Now imagine trying to find a friend in that marketplace simply by wandering around aimlessly. In a blizzard. Finding your friend was already plenty challenging; the environmental conditions can make it exponentially harder. You would likely find your friend eventually, but it would take some time. Now imagine that, instead of looking for your friend by yourself, you recruited all of your friends and family to help you. This could speed up the search. Recruit too many searchers, though, and you can overly complicate the hunt.
Detecting a single Listeria cell in an environmental sample presents similar challenges, and offers similar solutions. To help speed up the reaction, DETECT/L provides scores and scores of phage and sends them out on the hunt. However, our reaction requires a similar balance so as to not overcomplicate the hunt. Even with an ideal balance, finding a single, viable organism in a complex environment requires time. The larger and more complex the environment, the more time it will take.
Once our phage finds its target cell, the phage begins to run its biological program. This takes time, as well. Under the most ideal of laboratory conditions, a phage can run its full program (i.e. can detect a single cell of Listeria) in 60 minutes. Our development team is hard at work to optimize the search team and also find ways to speed up the biological program.
Making Efficient Factories
When our phage finds its target, it takes over the cellular machinery, turning the target cell into a miniature factory that churns out our reporter protein. (The cell is destroyed in this process. For questions on confirmation given this, check out this previous post.) And like any factory, if it’s not in good working order, it won’t be as productive. In the laboratory, we can introduce healthy cells to serve as efficient factories, or we can introduce damaged cells to serve as less efficient factories. As you would expect, the healthy cells produce more protein in a shorter period of time than the damaged cells. This protein is what the Sample6 Reader detects.
Food producers work hard to attempt to destroy any and all pathogens in their facility, so any microbes that make it past these defenses are typically damaged and broken. These damaged cells are not operating at capacity. The reagents provided in the DETECT/L kit are specifically formulated to help any still-viable target cells produce as much of the reporter protein as possible, however, for badly damaged cells this process can take longer. We continue to develop methods for optimizing production in damaged cells.
Seeing the Stars
The Sample6 DETECT/L assay recognizes a sample as positive for Listeria based on a luminescent biochemical reaction. In a controlled experiment, nothing in the sample interferes with the signal from this biochemical reaction. In environmental samples, the signal producing components can be disrupted at several points along the way and the signal itself can be blocked by other elements in the sample. When you are far from city lights, on a clear night, you can see millions of stars in the sky. If you are close to a city, or have cloud cover, it can be hard to see even a single nighttime star. The sun, however, is bright enough to be able to recognize its effect, even on a cloudy day. The same is true for the DETECT/L signal. The six-hour incubation ensures that the signal from a sample containing Listeria will be clear and bright, regardless of its environment. Our team is working on other approaches and chemistries so that we can speed up this process, as well.
The Path Forward
Creating a faster assay means bridging the gap between ideal laboratory conditions and true environmental samples for each of the three categories listed above. Improvements to the reagent formulation could mitigate signal inhibition, and could improve the efficiency of the cellular factories. Further optimization of the phage cocktail composition can improve the efficiency of the phage/cell interaction.
So the path forward is clear. Help phage find cells faster or more efficiently. Get those cellular factories running the phage’s program more efficiently. Neutralize the components that get in the way of our signal.
A six-hour incubation in an enrichment-free assay has shattered the previous standard. At Sample6, we’d like to do even more.
Together, we can make food safer.
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