Inappropriate and overuse of antibiotics has led to the emergence of drug-resistant strains and superbugs - a major public health problem that is in urgent need of solutions. Now, a team of researchers at McGill University in Montreal, Canada, suggests one solution may lie in the sap of trees that are abundant in North America.
Writing in the journal Applied and Environmental Microbiology, Nathalie Tufenkji, a chemical engineering professor, and colleagues describe how they found concentrated maple syrup extract makes disease-causing bacteria more susceptible to antibiotics.
The researchers made their discoveries from working with lab-based colonies of bacteria. But they hope the maple syrup extract will have the same effect on bacterial infections in human patients.
One potential benefit would be to reduce the use of antibiotics and thus slow the rate at which resistant strains emerge.
Maple syrup contains phenolic compounds, which are of considerable interest due to their antiseptic and antioxidant properties. Phenolic compounds play an important role in the growth and development of plants by helping to defend against pathogens.
Phenolic-rich extract made infection-causing bacteria susceptible to antibiotics
For the study, Prof. Tufenkji and colleagues made an extract of maple syrup comprising mainly phenolic compounds.
They bought the maple syrup at local markets in Montreal and kept it in the freezer until the start of each experiment where they removed a sample and put it through a series of steps to produce the phenolic-rich extract.
They then tested the extract on a number of infection-causing bacteria such as Escherichia coli and Proteus mirabilis - a common cause of urinary tract infection.
On its own, the maple syrup extract was mildly effective against the infection-causing bacteria.
But the maple syrup extract was even more effective against bacteria when combined with antibiotics.
The maple syrup extract and antibiotic combination was particularly effective at destroying biofilms - resistant communities that inhabit surfaces and are particularly hard to shift with antibiotics. Dental plaque is an example of a biofilm.
Biofilms commonly develop on catheters and cause difficult-to-treat urinary tract infections.
Maple syrup extract undermines bacteria in several ways
The researchers say the maple syrup extract affect the bacteria in a number of ways to make them more susceptible to antibiotics.
One effect that the extract has on bacteria is to make their cell membranes more porous. This makes it easier for the antibiotics to enter the microbial cells.
The maple syrup extract also shuts down the "efflux pumps" that the bacteria use to push any antibiotic that makes it through the membrane out of the cell.
And a third way that the extract weakens the bacteria is by reducing expression of genes linked to antibiotic resistance and virulence.
The researchers say the study is a first step that proves the concept. Now, more extensive and rigorous work needs to be done, eventually leading to clinical trials, before they can say what the effect will be in humans.
But Prof.Tufenkji says the findings "suggest a potentially simple and effective approach for reducing antibiotic usage," and adds:
"I could see maple syrup extract being incorporated eventually, for example, into the capsules of antibiotics."
Funds for the study came from the Natural Sciences and Engineering Research Council of Canada and the Canada Research Chairs program.