Food Safety Testing with Bacterial Vigilantes: Bacteriocins
By Alex Rogers
Food safety is a topic that concerns everyone. We all eat, thus we all should take into account the current state of the food that goes on our forks and into our bodies. If you’re eating right now, grab a forkful and take a look at your food. A real close look. Could there be something else on there, besides what you’re intending to eat? Some microscopic organism swimming through the mayonnaise in your potato salad? Miniature bugs, impossible to see with the naked eye, living in luxury on the surface of the beef in your fried rice?
Don’t get grossed out yet. Though it’s true that a one hundred percent bacteria free food is impossible as microorganisms exist everywhere (like the millions that colonize your skin and gut as is), the bacteria that cause harm are generally well controlled by the food production industry anything reaches your table. Generally, that is. The FDA displays recall data on their website; a list of foods pulled from the shelves every week to help prevent disease outbreak. But not every potential pathogen is detected before it goes out on the shelves or into the restaurants we visit, which is why events such as a widespread Listeria outbreak of Blue Bell dairy products or the multi-state Chipotle catastrophe in December of 2015 happened.
Why do these things occur? Most likely it is due to a lack of manpower and time. It’s physically impossible to check every every sample of food at food production companies. Even if it were possible to do it all, you simply couldn’t test every sample to begin with as then you’d have nothing left to sell. You could find negative results in all of your products but the one positive that somehow snuck by can shut it all down.
Besides an inability to test every company in the most thorough of manner, the other reason food products may go out contaminated and then force a recall boils down to the methods we use to make sure the product is safe. Numerous techniques used in the lab are extremely dated, think decades old. We use agar plates: jelly like substances that have been modified to select for the specific evil bacteria we try to avoid like E. coli O157:H7, Salmonella, or Listeria. But their precision is lacking, often picking out similar, non-harmful bacteria in the process and creating false positives, in addition to taking 5 – 7 days to get these final results.
We have expensive equipment that can break down the bacteria to its DNA and determine if the specific baddie is present at this subcellular level by matching up specific fragments to past data. Using this technique is much quicker than the agars mentioned above, but also takes a good deal more training to accomplish correctly and generally still relies on pre-enrichment or enrichment steps that allow the bacteria to grow in their most favorable conditions.
However, the most problematic of complications with the agars and the machines is that they just aren’t one hundred percent perfect even when everything is going right. They can’t detect bacteria below a certain number and that means a food sample contaminated with just a few cells of Listeria can pass inspection, go to the grocery store, experience exponential growth in colony size, and then cause sickness in future buyers of the product.
Innovation really needs to take place in the food safety field, all the way back to the first steps of just determining if there is a safety concern to begin with. Most of the new technology involves improving detection methods, the final step in a food safety assessment of a product. It gets the emphasis because this is the result we want: is the bacteria there or not? How much of it is there? Is this food safe to consume? In the end, though, improving detection has its limits and those limits are still the initial amount of bacteria present when that sample gets checked. Additionally, when checking for the safety of the food product, not only is the presence of bacteria important to know, but the type of bacteria as well.
What’s being done to improve these detection techniques then? A lot, actually. The most interesting of this new technology uses a bacteria’s own structure against it: bacteriocins. Bacteriocins are small bits of protein fragments isolated from bacteria and new research has shown they can be very effective at grabbing ahold of bacteria and keeping them in place to allow easy detection testing. How does it work? You coat a surface, say a tube, with the bacteriocins, attach some electrical monitoring device to the tube, and pass your food sample through the center. The bacteriocins, claws reaching out into the liquid of the food sample, grab and bind to the bacteria that passes by. These interactions create chemical changes that translate into electrical changes that trigger the monitoring device, thus alerting the watchful food microbiologist of the presence of the target bacteria.
There are two important parts to this method that make it invaluable in food safety testing. The first is the fact that the bacteriocin’s binding ability is species specific. Certain bacteriocins bind to certain bacteria and thus, if you’re seeing a reading, that means not only is bacteria present, but specifically the bacteria you are looking for. In addition, these chemical and electrical signals are detected at any interaction. What does this mean? Just one interaction of bacteria with bacteriocin will create a response, meaning detection can occur at exceptionally low initial levels of contamination.
Is this technology being used now? Unfortunately, no. A lot more testing needs to take place first. Results with actual food samples have been spotty, in no small part because of the mentioned complexity that comes with trying to tell if a food is safe or not. Not to fear, the research is ongoing and food products will be made safer and will be ensured at higher standards as time goes by. Food recalls and outbreaks may not stop completely, but they can be reduced to an infrequent and rare state. Take a deep breath, there are a lot of people whose one goal in life is to make sure the food you are eating is safe. Now take that bite still sitting on your fork.