'Simple reduction in antibiotic usage will not reverse antibiotic resistance. We need novel approaches to prevent the dissemination of bacterial antibiotic resistance'
(Peter Morenus/UConn Photo)
A new study led by Kumar Venkitanarayanan, dean of the College of Agriculture, Health and Natural Resources (CAHNR) has shown that plant-based antimicrobials are a promising avenue in the future of controlling antibiotic resistance in food-borne pathogens.
This work was published in Frontiers of Veterinary Science.
Following the widespread adoption of antibiotics in both agriculture and human medicine, many pathogens have evolved resistance to existing antibiotics. This has created a possible near future in which we could have no feasible treatments for a host of bacterial infections. This has led many scientists to look at alternative means of controlling bacteria and stopping the spread of antibiotic-resistant genes.
Bacteria can engage in something called horizontal gene transfer (HGT) where they can exchange useful genes - including genes that convey antibiotic resistance.
"Bacteria in any environment - in soil, in nature, or in the gut of humans or animals - can share their genetic information," says Venkitanarayanan, who is also a professor of animal science. "Simple reduction in antibiotic usage will not reverse antibiotic resistance. We need novel approaches to prevent the dissemination of bacterial antibiotic resistance, especially through horizontal gene transfer."
One prominent example of this phenomenon is antibiotic-resistant Salmonella, a food-borne pathogen that causes illness in approximately 1.3 million Americans each year, which could potentially transfer antibiotic resistance through HGT to commensal bacteria in gut, including E. coli.
"We have seen that once bacteria develop resistance to an antibiotic, they keep propagating it," Venkitanarayanan says. "They keep sharing it. They keep transmitting it to millions of other bacteria."
Venkitanarayanan's lab focuses on phytochemicals - chemicals derived from plants. One benefit of using phytochemicals is that, since the phytochemicals he works with are derived from edible plants, they are safer than synthetic chemicals for use in food production - even for organic producers.
Venkitanarayanan found that a blend of phytochemicals derived from coconut, cinnamon, cranberry juice, and oregano are an effective treatment to prevent HGT in poultry production.
The study shows that the phytochemicals were able to reduce the rate of HGT from antibiotic resistant Salmonella to E. coli to below 50% in each environment the researchers tested.
In this study, Venkitanarayanan looked at adding the phytochemicals to manure, water, and as a dietary supplement. This approach targets three critical locations where bacteria frequently grow on poultry farms, including in the guts of chickens.
"My objective was to show that phytochemicals are effective at preventing the dissemination of antibiotic-resistant genes by HGT from pathogenic bacteria to commensal [non-pathogenic] bacteria in the gut," Venkitanarayanan says.
The phytochemical blend Venkitanarayanan used attacks bacteria through multiple mechanisms, giving it an advantage over traditional antibiotics. This also makes it harder for bacteria to develop resistance.
"Many phytochemicals, because they have multiple functional groups in their structure, they could attack bacteria by multiple mechanisms," Venkitanarayanan says.
The next step for this work is to conduct an experiment using a large number of chickens to see how well-tolerated this combination of phytochemicals is as a feed additive, as well as confirming its efficacy.
This study is the first time someone has looked at preventing HGT in foodborne pathogens in a food production environment. The work also uses a One Health approach, considering the interconnectedness of human, animal, plant, and environmental health.
"I believe we are targeting the base of the problem," Venkitanarayanan says. "Reducing the use of antibiotics is always [a] good [strategy] to reduce antibiotic resistance. But the antibiotic-resistant genes have already been created by bacteria, and they keep disseminating. Our research targets the spread of that."
This work was supported by USDA-NIFA as part of a $10 million investment in sustainable poultry production.
This work relates to CAHNR's Strategic Vision area focused on Ensuring a Vibrant and Sustainable Agricultural Industry and Food Supply.
