Tree Resin Compound Defeats Drug-Resistant Bacteria in Lab Tests

A new compound made from tree resin kills almost 100% of drug-resistant bacteria without harming healthy tissue, laboratory studies suggest.

Made into a film, this nanocellulose could be used as a wound dressing or as a protective surface on medical implants.

Researchers have been surprised by its efficacy in the studies so far. “It was like a wonder,” Ghada Hassan, a doctoral student in pharmacy at the University of Helsinki in Finland, told Medscape Medical News. She and her colleagues published their findings in Applied Bio Materials .

Bacteria are able to evolve resistance to new antibiotics sometimes within only a few years. Infection by methicillin-resistant Staphylococcus aureus (MRSA) is a particular problem in pressure ulcers and wounds from prosthetic, plastic, and reconstructive surgery.

In search of a medicine that could retain its efficacy against these difficult-to-treat bacterial strains, Hassan noticed in Finnish pharmacies a traditional treatment for small wounds made from the resin of conifers. References to resin as a wound dressing date back 500 years in Finland, and there are many favorable anecdotal reports, she said.

Trees produce the resin when injured to protect themselves from infection. As the resin has maintained its effectiveness for millions of years, Hassan reasoned that bacteria could not easily evolve resistance to it.

However, raw tree resin would be difficult to use in many medical procedures. “For implants you cannot open the patient and pour in some resin there and then close the patient and hope it will be well,” she said.

Using dehydroabietic acid derivatives, Hassan and her colleagues modified the resin, creating a film that could be used both in wound dressings and as a coating for implants.

In an early test, they applied MRSA directly to sheets of the modified nanocellulose and found that 99.999% of the bacteria died.

In a second experiment, they created an artificial dermis containing horse plasma on which they cultivated MRSA. They then applied a film made up of the experimental nanocellulose and found that it was highly effective in killing the bacteria.

In a third experiment they placed human erythrocytes directly on sheets of the modified nanocellulose and found that most of the erythrocytes survived, as did skin fibroblasts in similar experiments.

In further experiments, they found that the nanocellulose could kill multiple strains of S. aureus, as well as Escherichia coli.

The novel compound seems to damage bacteria through multiple mechanisms, making it more difficult for the organisms to evolve resistance, Hassan said.

Early, but Good Potential

The research suggests a lot of potential for the new compound, said Aaron Glatt, MD, a professor of medicine at the Icahn School of Medicine at Mount Sinai in New York City and a spokesperson for the Infectious Diseases Society of America. But it must undergo clinical trials before it can realize that potential, he told Medscape Medical News.

“This paper is certainly no indication that it will become the definitive answer,” he said. “What looks good in a laboratory, what looks good in a test tube, let’s put it to the test in real life.”

In addition, even if it passes muster in clinical trials, it will have to show cost-effectiveness, said Barry Kreiswirth, PhD, adjunct faculty member of the department of medicine at New York University in New York City.

“As an example, we know that using copper bed rails and other copper products in a hospital setting reduces infections, but no one is willing to pay the extra cost to copperize a hospital bed,” he told Medscape Medical News in an email.

That said, the modified nanocellulose is less expensive and less toxic than copper and silver, which are also being tested as a coating for implants, Hassan said. “Cellulose is the most abundant polymer on Earth,” she said. And unlike some other material under consideration, its bacteria-killing ingredients don’t leach out into the environment, so it may stay effective for a longer time, she said.

Her laboratory is currently closed as a protection against COVID-19, but when it opens she would like to next test the material against pathogenic fungi and viruses.

ACS Appl. Bio Mater. 2020;3:4095−4108. Full text

Hassan, Kreiswirth, and Glatts reported no relevant financial relationships.

Laird Harrison writes about science, health, and culture. His work has appeared in national magazines, in newspapers, on public radio, and on websites. He is at work on a novel about alternate realities in physics. Harrison teaches writing at the Writers Grotto. Visit him at www. lairdharrison.com or follow him on  Twitter: @LairdH

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