Phages, which are harmless viruses that destroy specific bacteria, are becoming useful tools to protect our food supply.
Every year, one in seven people in America comes down with a foodborne illness, typically caused by a bacterial pathogen, including E.Coli, listeria, salmonella, or campylobacter. That adds up to 48 million people, of which 120,000 are hospitalized and 3000 die, according to the Centers for Disease Control. And the variety of foods that can be contaminated with bacterial pathogens is growing too. In the 20th century, E.Coli and listeria lurked primarily within meat. Now they find their way into lettuce, spinach, and other leafy greens, causing periodic consumer scares and product recalls. Onions are the most recent suspected culprit of a nationwide salmonella outbreak.
Some of these incidents are almost inevitable because of how Mother Nature works, explains Divya Jaroni, associate professor of animal and food sciences at Oklahoma State University. These common foodborne pathogens come from the cattle's intestines when the animals shed them in their manure—and then they get washed into rivers and lakes, especially in heavy rains. When this water is later used to irrigate produce farms, the bugs end up on salad greens. Plus, many small farms do both—herd cattle and grow produce.
"Unfortunately for us, these pathogens are part of the microflora of the cows' intestinal tract," Jaroni says. "Some farmers may have an acre or two of cattle pastures, and an acre of a produce farm nearby, so it's easy for this water to contaminate the crops."
Food producers and packagers fight bacteria by potent chemicals, with chlorine being the go-to disinfectant. Cattle carcasses, for example, are typically washed by chlorine solutions as the animals' intestines are removed. Leafy greens are bathed in water with added chlorine solutions. However, because the same "bath" can be used for multiple veggie batches and chlorine evaporates over time, the later rounds may not kill all of the bacteria, sparing some. The natural and organic producers avoid chlorine, substituting it with lactic acid, a more holistic sanitizer, but even with all these efforts, some pathogens survive, sickening consumers and causing food recalls. As we farm more animals and grow more produce, while also striving to use fewer chemicals and more organic growing methods, it will be harder to control bacteria's spread.
"It took us a long time to convince the FDA phages were safe and efficient alternatives. But we had worked with them to gather all the data they needed, and the FDA was very supportive in the end."
Luckily, bacteria have their own killers. Called bacteriophages, or phages for short, they are viruses that prey on bacteria only. Under the electron microscope, they look like fantasy spaceships, with oblong bodies, spider-like legs and long tails. Much smaller than a bacterium, phages pierce the microbes' cells with their tails, sneak in and begin multiplying inside, eventually bursting the microbes open—and then proceed to infect more of them.
The best part is that these phages are harmless to humans. Moreover, recent research finds that millions of phages dwell on us and in us—in our nose, throat, skin and gut, protecting us from bacterial infections as part of our healthy microbiome. A recent study suggested that we absorb about 30 billion phages into our bodies on a daily basis. Now, ingeniously, they are starting to be deployed as anti-microbial agents in the food industry.
A Maryland-based phage research company called Intralytix is doing just that. Founded by Alexander Sulakvelidze, a microbiologist and epidemiologist who came to the United States from Tbilisi, the capital of Georgia, Intralytix makes and sells five different FDA-approved phage cocktails that work against some of the most notorious food pathogens: ListShield for Listeria, SalmoFresh for Salmonella, ShigaShield for Shigella, another foodborne bug, and EcoShield for E.coli, including the infamous strain that caused the Jack in the Box outbreak in 1993 that killed four children and sickened 732 people across four states. Last year, the FDA granted its approval to yet another Intralytix phage for managing Campylobacter contamination, named CampyShield. "We call it safety by nature," Sulakvelidze says.
Intralytix grows phages inside massive 1500-liter fermenters, feeding them bacterial "fodder."
Photo credit: Living Radiant Photography
Phage preparations are relatively straightforward to make. In nature, phages thrive in any body of water where bacteria live too, including rivers, lakes and bays. "I can dip a bucket into the Chesapeake Bay, and it will be full of all kinds of phages," Sulakvelidze says. "Sewage is another great place to look for specific phages of interest, because it's teeming with all sorts of bacteria—and therefore the viruses that prey on them."
In lab settings, Intralytix grows phages inside massive 1500-liter fermenters, feeding them bacterial "fodder." Once phages multiply enough, they are harvested, dispensed into containers and shipped to food producers who have adopted this disinfecting practice into their preparation process. Typically, it's done by computer-controlled sprayer systems that disperse mist-like phage preparations onto the food.
Unlike chemicals like chlorine or antibiotics, which kill a wide spectrum of bacteria, phages are more specialized, each feeding on specific microbial species. A phage that targets salmonella will not prey on listeria and vice versa. So food producers may sometimes use a combo of different phage preparations. Intralytix is continuously researching and testing new phages. With a contract from the National Institutes of Health, Intralytix is expanding its automated high-throughput robot that tests which phages work best against which bacteria, speeding up the development of the new phage cocktails.
Phages have other "talents." In her recent study, Jaroni found that phages have the ability to destroy bacterial biofilms—colonies of microorganisms that tend to grow on surfaces of the food processing equipment, surrounding themselves with protective coating that even very harsh chemicals can't crack.
"Phages are very clever," Jaroni says. "They produce enzymes that target the biofilms, and once they break through, they can reach the bacteria."
Convincing the FDA that phages were safe to use on food products was no easy feat, Sulakvelidze says. In his home country of Georgia, phages have been used as antimicrobial remedies for over a century, but the FDA was leery of using viruses as food safety agents. "It took us a long time to convince the FDA phages were safe and efficient alternatives," Sulakvelidze says. "But we had worked with them to gather all the data they needed, and the FDA was very supportive in the end."
The agency had granted Intralytix its first approval in 2006, and over the past 10 years, the company's sales increased by over 15-fold. "We currently sell to about 40 companies and are in discussions with several other large food producers," Sulakvelidze says. One indicator that the industry now understands and appreciates the science of phages was that his company was ranked as Top Food Safety Provider in 2021 by Food and Beverage Technology Review, he adds. Notably, phage sprays are kosher, halal and organic-certified.
Intralytix's phage cocktails to safeguard food from bacteria are approved for consumers in addition to food producers, but currently the company sells to food producers only. Selling retail requires different packaging like easy-to-use spray bottles and different marketing that would inform people about phages' antimicrobial qualities. But ultimately, giving people the ability to remove pathogens from their food with probiotic phage sprays is the goal, Sulakvelidze says.
It's not the company's only goal. Now Intralytix is going a step further, investigating phages' probiotic and therapeutic abilities. Because phages are highly specialized in the bacteria they target, they can be used to treat infections caused by specific pathogens while leaving the beneficial species of our microbiome intact. In an ongoing clinical trial with Mount Sinai, Intralytix is now investigating a potential phage treatment against a certain type of E. coli for patients with Crohn's disease, and is about to start another clinical trial for treating bacterial dysentery.
"Now that we have proved that phages are safe and effective against foodborne bacteria," Sulakvelidze says, "we are going to demonstrate their potential in therapeutic applications."
This article was first published by Leaps.org on October 27, 2021.
Dr. Andrew Brooks of RUCDR Infinite Biologics holds up a saliva sample.
The patient tilts back her head and winces as the long swab stick pushes six inches up her nose. The tip twirls around uncomfortably before it's withdrawn.
"Our saliva test can detect the virus in asymptomatic and pre-symptomatic cases."
A gloved and gowned healthcare worker wearing a face shield and mask tells the patient that she will learn whether she is positive for COVID-19 as soon as the lab can process her test.
This is the typical unpleasant scenario for getting a coronavirus test. But times are rapidly changing: Today, for the first time, the U.S. Food and Drug Administration cleared one company to sell saliva collection kits for individuals to use at home.
Scientists at the startup venture, RUCDR Infinite Biologics at Rutgers University in New Jersey, say that saliva testing offers an easier, more useful alternative to the standard nasal swab.
"Our saliva test can detect the virus in asymptomatic and pre-symptomatic cases," said Dr. Andrew Brooks, chief operating officer at RUCDR.
Another venture, Darwin BioSciences in Colorado, has separately developed an innovative method of testing saliva for the coronavirus that causes COVID-19.
Saliva testing can allow earlier detection to identify people who may not know they are contagious, say scientists at both companies. In addition, because patients spit into a tube or cup, saliva testing is safer for healthcare workers than taking swabs. This frees up scarce personal protective equipment (PPE) for use elsewhere. Nasal swabs themselves have been in scarce supply.
Saliva testing, if it becomes widespread, potentially could mean opening society sooner. The more ubiquitous testing becomes across the population, experts say, the more feasible it becomes for public health officials to trace and isolate contacts, especially of asymptomatic cases. Testing early and often will be essential to containing emerging hot spots before a vast outbreak can take root.
Darwin Biosceiences is preparing to seek an FDA Emergency Use Authorization (EUA) this month for its patented "CoVScreen" testing system, which potentially could be available to labs nationally by mid-summer.
Meanwhile, Infinite Biologics will now begin selling kits to consumers for home collection, upon order by a physician. The FDA said that the company's saliva test was as accurate as the nasal swab method used by health care professionals. An FDA summary documenting the company's data reported: "There was 100% positive and negative agreement between the results obtained from testing of saliva and those obtained from nasopharyngeal and oropharyngeal swabs."
The greatest scientific advantage, said Dr. Brooks, is that nasal and oral swabs only collect the surface area where the swab goes, which may not be the place with most viral load. In contrast, the virus occurs throughout a saliva sample, so the test is more trustworthy.
The lab at Rutgers can process 20,000 tests a day, with a 48-hour turnaround. They have 75,000 tests ready to ship now.
The Leap: Detecting Sickness Before You Feel It
"We wanted to create a device that could detect infections before symptoms appeared," explained Nicholas Meyerson, co-founder and CEO of Darwin.
For more than 300 years, he said, "the thermometer was the gold standard for detecting disease because we thought the first sign of illness was a fever. This COVID-19 pandemic has proven that not all pathogens cause a fever. You can be highly contagious without knowing it."
"The question is whether we can scale up fast enough to meet the need. I believe saliva testing can help."
Therefore, Meyerson and co-founder Sara Sawyer from the University of Colorado began to identify RNA biomarkers that can sense when a pathogen first enters a molecule and "sets off alarms." They focused on the nucleic acids concentrated in saliva as the best and easiest place to collect samples for testing.
"The isothermal reaction in saliva takes place at body or room temperature," he said, "so there's no need for complicated testing machinery. The chemical reaction can be read out on a paper strip, like a pregnancy test -- two stripes if you're sick, and one stripe if you're okay."
Before the pandemic, limited but successful human trials were already underway at CU in Boulder and at the CU Anschutz Medical Campus east of Denver. "This was our proof of concept," he said.
Darwin was founded in March and has secured enough venture capital to concentrate protype development on detecting the virus causing COVID-19. So far, said Meyerson, "Everything works."
A small double-blind test of 30 samples at CU produced 100 percent accuracy. "I'm not sure if that will hold true as we go into clinical trials," he said, "but I'm confident we will satisfy all the requirements for at least 95 percent clinical validation."
The specific "CoVStick" test strips will roll out soon, he said: "We hope before the second wave of the pandemic hits."
The broader saliva test-strip product from Darwin, "SickStick," is still one to two years away from deployment by the military and introduction into the consumer drugstore market for home use, said Meyerson. It will affordably and quickly detect a range of viral and bacterial infections.
An illustration of the "CoVStick."
(Darwin Biosciences)
A Potential Game Changer
Society needs widespread testing daily, said George Church, founding core faculty of the Wyss Institute for Biologically Inspired Engineering at Harvard University. Speaking at an online SynBioBeta webinar in April, he urged developing stockpiles of testing kits for home use.
As for any potential of false positives, Church said a much bigger risk is not having enough tests.
"Saliva testing is going to speed up the timeline for opening society a lot," said Meyerson. "People need to self-collect samples at home. A lot more people are going to be willing to spit into a tube than to push a swab six inches up their own nose."
Brooks, of Rutgers, addressed the big picture. "It's critical that we open society as soon as possible to minimize the economic impact of the pandemic. Testing is the surest and safest path. The question is whether we can scale up fast enough to meet the need. I believe saliva testing can help."
