Su­per­bugs are be­com­ing more re­sis­tant to an­tibi­otics by the day. Cassandra Quave is search­ing for a so­lu­tion in forgotten herbal reme­dies

BBC Earth (Asia) - - Science -

“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.”

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