Rapid Listeria testing technology continues to improve
If a swab test performed in a plant comes back positive, waiting to confirm it’s a pathogenic strain can be damaging and costly.
Listeria is everywhere, but not all strains are particularly dangerous. It’s one thing to find Listeria in your plant that someone tracked in on his boots, but suppose it’s Listeria monocytogenes (Lm) in a machine or on the wall—that can shut your plant down for a while, during which you frantically clean and hope the FDA inspector doesn’t make an unplanned visit.
Dr. Jack Regan, founder and CEO of LexaGene, a rapid-testing technology company, has been working to speed up testing, simplify it and identify pathogens. Regan holds a PhD in biomedical sciences, is the inventor of LexaGene’s rapid-testing technology and has held leadership positions at Lawrence Livermore National Laboratory, QuantaLife, Bio-Rad, Applied Biosystems and Life Technologies.
LexaGene recently unveiled its LX6 alpha prototype, which uses microfluidic technology to analyze genetically six liquid samples, either inserted at the same time or sequentially. The system is capable of monitoring up to 22 predefined organisms, such as E. coli, Salmonella and Listeria. Able to be run by a novice, the LX6 can determine if you have the bad species of Listeria—i.e., Lm—in your plant. The system can also look for specific strains of E. coli, for example, E. coli O157: H7 or E. coli O104:H4.
Dr. Regan recently discussed more particulars on this invention and its capabilities.
FE: In a nutshell, describe the evolution of the technology leading up to your LX6 analyzer.
Dr. Jack Regan: LX6 is a fourth-generation microfluidic instrument. The first two generations were developed at Lawrence Livermore National Laboratory with $19M in government funding for bio-threat detection. One of these instruments, called APDS, was validated by the Department of Homeland Security and adopted to be part of the government’s BioWatch Program. The third generation was a research tool used to detect respiratory pathogens in patients visiting the emergency department of the UC Davis Medical Center. LX6’s design is much more powerful than these predecessor instruments, because it can process more samples at the same time, screen for more pathogens and return results more quickly.
FE: What were your intents on the design of LX6?
Regan: I wanted to design a simple-to-use instrument that could detect many pathogens in just one hour. I also wanted it to be flexible, so that end users can customize their genetic screens to meet their needs.
FE: Does this system have the ability to distinguish various species and/or strains of bacteria? Please explain.
Regan: Our LX6 instrument performs real-time quantitative PCR [qPCR], which is able to distinguish two strains of bacteria even if they have very minor differences in their genetic code.
FE: How does a user set up the analyzer to detect specific bacteria and their species?
Regan: Operators simply need to load a liquid sample and a sample preparation cartridge onto the instrument and then use the touchscreen monitor to initiate sample processing. Together, this only takes about 30 seconds.
FE: What are the sampling requirements? Must they be liquid samples? What about powders—can they be mixed with water for testing, e.g., powdered milk, cocoa? Can you use a swab on surfaces?
Regan: We anticipate being able to process any liquid sample that doesn’t have too high of a viscosity or too many large particulates. In the food safety industry, we anticipate testing the media in which swabs are swirled, liquids used to suspend powders and liquids used to wash grains, fruits, vegetables and even meat products. We know there is a lot of interest in processing milk, and we are working on a different cartridge design to handle this difficult matrix.
FE: How do you avoid sampling errors (false negatives) where only a couple of bacteria might exist in a sample?
Regan: We will include assays to detect the RNA of genes present at hundreds to thousands of copies per cell, such as 16S rRNA, which will help improve sensitivity and avoid false negatives. Conversely, our instrument will also be great at avoiding false positives, because the instrument detects up to 22 targets per sample, so we can target the same pathogen with multiple assays, thereby improving our confidence in any positive result.
FE: You had mentioned that the analyzer can do continuous liquid sampling. How so?
Regan: We could configure our system for continuous liquid sampling, but it would require adding a feeder module onto the system that automatically loads new sample preparation cartridges onto the instrument. With such a feeder module, the system would be fully autonomous—allowing for a completely hands-free approach.
FE: How many sampling streams can run simultaneously? When one is finished, how soon can the next sample be tested?
Regan: LX6 will process six samples at a time in an on-demand fashion, but the design can easily be expanded to process up to 12 samples at a time. After the instrument reports a result for a tested sample, it automatically initiates a cleaning process that takes about seven minutes before that lane of the instrument can be used to process the next sample.
FE: What are some good applications beyond checking water from a leaky roof, puddles on the floor or condensation on the walls? Beverages? What food matrices might be applicable in the future?
Regan: In the food safety industry, we expect our technology to first be used on the media from swabs that are collected as part of a standard environmental monitoring program, as well as on the water used to rinse fruits, vegetables and grains. We also expect it to be used on wine and beer to detect spoiling. In the future, once we have developed and validated a sample preparation cartridge for processing milk, we expect to expand into the milk testing business.
FE: Are you now working with food and beverage processors? Do you need some partners to do beta testing?
Regan: We’ve been talking for some time with food and beverage companies, and they have validated the need for advanced technologies to better test their facilities and food products. We welcome interested companies to contact us to be added to the beta test list, where they will be able to test our technology—free of charge—for a period of time to see if it meets their expectations. If any of your readers are interested, they can contact the company at firstname.lastname@example.org.
FE: Anything else?
Regan: Yes, our technology is intended to provide food safety officers with a report in just one hour on the level of DNA (or RNA) detected from potentially dangerous pathogens. This information is intended to be used to assign a risk level for a tested sample. Knowing this information—in just one hour’s time—will allow food companies to make informed decisions on how to handle their food products and cleaning procedures, which will make them more efficient. We also believe that more sensitive detection will make food producers less likely to release a contaminated food item to consumers, which invariably leads to an expensive recall and irreparable brand damage. A small investment on in-house automated genetic testing could possibly prevent millions in losses.
For more information, visit LexaGene at www.lexagene.com