THE NEW HERBALIST
Superbugs are becoming more resistant to antibiotics by the day. Cassandra Quave is searching for a solution in forgotten herbal remedies
“Over time and within these cultures, they’ve become attuned to these plant compounds and to the resolution of disease, and I think that’s exciting”
Roaming around southern Italy, picking up interesting plants and having a chat with the locals might sound like a holiday, but ethnobotanist Dr Cassandra Quave assures us it’s not. “You know, it’s not a vacation,” she says. “It’s really hard work.” It’s also vital work – Quave and her team from Emory University in Atlanta, Georgia, are scouring the Mediterranean for medicines that could help tackle the mounting crisis of antibiotic resistance. In the US and Europe alone, 50,000 people die each year from infections caused by resistant bacteria they picked up during a hospital stay. Without new treatments, global deaths will soon soar into the millions. Quave believes that those treatments can be found in plants.
A self-described history of medicine geek, Quave talks to local people about plants that have been used, often for centuries, in their traditional medicines. In this way, she hopes to track down those with the greatest potential for fighting infection. She admits other researchers looking for new antibiotics are dismissive about her approach because they think plants have already been found lacking. “But no one has looked at the scope of plants that we’re looking at, and some of these are [already] being used in traditional medicines for fighting infection,” says Quave. “Also, no one has looked at the other potential ways that these might be acting beyond just killing bugs.” What’s curious about some of the plant extracts that Quave has tested is that they work in a different way to the antibiotics used in clinics today. As they stop short of killing their targets – working instead against microbial communication systems – the bugs shouldn’t evolve resistance to these extracts, making them an exciting prospect for future antibiotics.
The approach could work against different species of bacteria, but top of Quave’s hit list is methicillin-resistant Staphylococcus
aureus, more commonly known as MRSA. Quave has something of a personal vendetta against the ‘staph’ bug: at the age of three, she was hospitalised for months with an MRSA infection after having part of her right leg amputated. Later, she got involved with science fair projects and became completely absorbed in the idea of bacterial resistance via news stories about E. coli-infested burgers. “I was an odd kid!” she jokes. MRSA is notorious as the hospital ‘superbug’ that causes dangerous skin infections by using wounds, burns, drips and catheters to gain access to deeper layers of the skin. Quave regularly receives letters and emails from patients’ frightened relatives, who are desperate to try any new treatment for the disease. It’s a constant reminder that her ultimate goal is helping people, not making the next blockbuster drug.
So has Quave found anything on her Italian field trips that could help those individuals suffering from lifethreatening skin infections? “In Italy, we asked people ‘what plants do you put on the skin to treat infections, rashes... all of these kinds of things’,” she says. “And sweet chestnut came up.” Yes, the exact same plant that gives us roasted chestnuts at Christmas. In a recent paper, Quave’s team showed that sweet chestnut leaf extract can block some of the toxic effects of MRSA and, in a mouse infected with the bug, decrease the area of skin affected, all without killing the bacteria. They’ve now narrowed it down to five compounds that seem to be responsible for most of the benefit.
Quave, who practises what she preaches, making medicinal teas from plants she grows in her own garden, also hopes to validate some age-old remedies. “This is giving cultural value to people who have been using these remedies for centuries. Perhaps a healer doesn’t understand the intricacies of bacterial signalling, but over time and within these cultures, they’ve become attuned to these plant compounds and to the resolution of disease, and I think that’s exciting.”