The process of making food safe is never-ending, and as a result, food safety experts, microbiologists, and industry insiders are constantly searching for new ways to improve the food safety system in the United States.
Within the last few years, food growers and producers have begun to use a novel means of improving food safety through the use of bacteriophages. Also known as lytic viruses or phages, bacteriophages take up residence inside certain strains of foodborne bacteria, begin multiplying, and eventually destroy the bacterial cell.
The consensus among microbiologists is that phages do not have any known adverse effects on humans, animals, or the environment, and in fact gravitate toward wherever bacteria live, including the human body, water, and the environment.
For this reason, many scientists and food safety experts predict that bacteriophages could become a useful tool in the reduction of dangerous pathogens in beef, cold cuts, produce, and more.
Manan Sharma, a Research Microbiologist for the United States Department of Agriculture (USDA), has conducted phage tests on a variety of produce and has concluded that phage treatments could be effective in killing E. coli O157:H7 in a produce commodity. “The treatments reduced pathogens on the samples of fresh-cut cantaloupe by 100-fold over untreated controls,” said Sharma in a USDA release.
Sharma’s test studies also found that phages could have an equally potent effect on refrigerated fresh-cut lettuce, the source of a current E. coli O145 outbreak that has sickened 30 people in 23 states.
“The results indicate that bacteriophage treatments can kill E. coli O157:H7 on the surface of leafy greens at the same levels as on the fresh-cut cantaloupe,” he said.
Biotechnology companies have long pressed for the use of bacteriophages in the public food supply, but the federal government has so far allowed the use of only two products.
In 2006, the Food and Drug Administration (FDA) approved a bacteriophage mixture, called a “lytic cocktail,” in a spray-on form designed to reduce the presence of Listeria monocytogenes bacteria in meat and deli products.
Then in 2007, the USDA approved a bacteriophage product that OmniLytics Company designed to be sprayed, misted, or washed onto cattle hides to reduce the presence of E. coli bacteria.
“It’s a good sign that FDA has approved phage-based products for use recently,” Sharma told Food Safety News. “I think that bacteriophages–and their derived products, like enzymes that attack bacterial cells walls–can be an effective intervention against foodborne pathogens.”
Some microbiologists, however, are concerned that the widespread use of bacteriophages in the food supply could result in an increased resistance of bacteria to phage treatment.
Sharma, however, believes the “cocktail” of bacteriophages administered simultaneously to food products is varied enough to prevent a resistance build-up in targeted bacteria.
“Most scientists believe that using multiple phages specific for a pathogen in a “cocktail” helps address this concern,” he said. “This way if bacterial strains become resistant to one phage, there are still multiple phages to which they remain sensitive. Unlike with antibiotics, bacteria and bacteriophages are constantly evolving, so there is always the likelihood that a lytic phage can be identified against foodborne pathogens.”
“I think in the right setting, bacteriophages can be extremely effective,” he continued. “We have shown that bacteriophages can kill E. coli O157:H7 on the surface of cut lettuce within one hour. Others have shown their effectiveness on produce and meats. Bacteriophages are naturally present in a variety of foods, so I think there is a very strong likelihood that more lytic phages for specific pathogens could be identified relatively easily.”
Photo: The bacteriophage T4 is preparing to infect its host cell. The structure of bacteriophage T4 is derived from three-dimensional cryo-electron microscopy reconstructions of the baseplate, tail sheath and head capsid, as well as from crystallographic analyses of various phage components. The baseplate and tail proteins are shown in distinct colors. Accessed from the National Science Foundation Website. Credit: Purdue University and Seyet LLC. The animation is based on both recent discoveries and extensive earlier work by a large number of investigators.