From household cleaners to cosmetics, essential oils derived from plants can be used in many ways. Now, research funded through the Government of Canada's Genomics Research and Development Initiative (GRDI) is showing how essential oils can play a role in Canada's actions to limit the spread of antimicrobial resistance (AMR).
Antimicrobial resistance: AMR
Led by Agriculture and Agri-Food Canada (AAFC) Research Scientist Dr. Moussa Diarra, the work on essential oils is among a series of interlocking studies conducted as part of the GRDI Antimicrobial Resistance Research project (GRDI-AMR). This 5-year project involves more than 2 dozen scientists from 5 federal departments collaborating to enhance Canada's capacity to address AMR, the growing number of bacteria and other pathogens that are developing resistance to an ever‑wider range of antibiotics and other antimicrobials.
Overuse and misuse of antibiotics are major contributors to AMR—the more we use antibiotics, the more likely bacteria resistant to them are selected.
AMR in poultry
The emergence of AMR is a serious and increasing global public health issues. The World Health Organization recognizes AMR as one of the most serious global threats to the prevention, control and treatment of infectious diseases. The poultry industry, along with AAFC, is an active player in Health Canada's action plan to reduce the use of antibiotics in Canada.
For decades, dietary antibiotics have been widely used in poultry production to promote bird growth and performance and to prevent economically important diseases. The spread of antibiotic resistance threatens human health, and efforts to restrict dietary antibiotics in poultry production in Canada are underway. Part of this effort is research to identify safe and effective alternatives to antibiotics.
Dr. Diarra's research, for example, reported strains of Salmonella, Escherichia coli and Enterococcus bacteria in chickens that showed resistance to antibiotics used to treat infections in both animals and people. Both Salmonella and E. coli are common in chickens, and can infect humans through improper handling of raw meat, or eating undercooked meat—potentially adding to the spread of AMR bacteria among humans.
In support of the industry's own efforts to reduce its use of antibiotics, the research led by Dr. Diarra has identified substances that could replace some, if not all of the antibiotics still in use.
Blueberries and cranberries
Prior to the research on essential oils, Dr. Diarra, working in collaboration with fellow scientists at AAFC, the University of Guelph, McGill University and the Centre de recherche en sciences animales de Deschambault, demonstrated the potential benefits of adding blueberry and cranberry pomaces and their extracts to the birds' diet.
"Pomace is what's left over after the juice has been squeezed from the berries," explains Dr. Diarra. "In addition to increasing the birds' fibre intake—promoting overall gut health—genomics technologies enabled us to see how these berry products work at the molecular level to restrict the growth of Salmonella bacteria. There was also evidence that berry products promoted gut health and acted to strengthen chickens' overall immune system, making them better able to fight infections."
Cinnamon trees and lemongrass
In their most recent studies, Dr. Diarra and his collaborators—including Dr. Joshua Gong, Dr. Qi Wang, Dr. Hai Yu, Dr. Xianhua Yin, Dr. Attiq Rheman, and Dr. Chongwu Yang at AAFC, as well as researchers from the Canadian Food Inspection Agency, the University of Manitoba and the Centre de recherche en sciences animales de Deschambault, added 2 essential oils to the birds' diet: cinnamaldehyde, from the bark of cinnamon trees, and citral, which is found in a number of plants, including lemongrass.
The findings were, in Dr. Diarra's words, "really significant."
"Using microbiota analysis and whole genome sequencing of E. coli from the content of the birds' intestinal tracts, we found that adding these essential oils to the birds' feed resulted in a sizeable reduction in the population of AMR E. coli," says Dr. Diarra. "At the same time, we also saw an increase in the number and diversity of beneficial micro-organisms in the birds' digestive tracts."
For more on Dr. Diarra's work, read these 2 stories:
Industry: research is essential
At the Canadian Poultry Research Council, Executive Director Dr. Bruce Roberts says addressing antimicrobial resistance and animal welfare are the industry's "2 highest priorities."
"The industry has reduced its use of antibiotics by a significant amount in recent years," says Dr. Roberts, "But until another way to protect the birds' health is found, they cannot be eliminated entirely. That's why the GRDI-funded research at AAFC, and the exceptional work being done by Dr. Diarra and his collaborators especially, is so important."