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A strain of the antibiotic-resistant bacterium MRSA seems to have evolved in hedgehogs in the early 1800s – long before the introduction of antibiotics. The finding demonstrates how antibiotic resistance can occur in nature – and underlines the need for cautious use of antibiotics.

Staphylococcus aureus is a bacterium that can live harmlessly on our skin and up our noses. But it can sometimes cause infections of the skin and gut.

Methicillin-resistant Staphylococcus aureus (MRSA) is a type of these bacteria that can’t be killed with antibiotics like methicillin. As a result, it can cause infections that can be difficult to treat. Most cases are picked up in hospitals, and some are fatal.

Over the past decade or so, researchers have begun to find a type of MRSA known as mecC-MRSA in all sorts of wildlife, including boars, storks, snakes and hedgehogs.

While mecC-MRSA seems to be relatively uncommon in most of these species, researchers have found it in plenty of hedgehogs. To find out why, Ewan Harrison at the University of Cambridge and his colleagues studied swab samples from 276 European hedgehogs (Erinaceus europaeus) from 10 European countries and New Zealand.

Hedgehogs from Greece, Romania, France, Italy and Spain didn’t seem to have any mecC-MRSA on their skin. But others did – 66 per cent of hedgehogs from England and Wales tested positive for the bacteria, for example.

These animals also had a fungus called �հ�������DZ���ٴDz���������Բ����� living on their skin. This fungus is known to produce chemicals that can kill bacteria.

In experiments, the team found that T. erinacei made an antibiotic called KPN that could kill mecC-MRSA only when the bacterium’s genes for antibiotic resistance were removed. This suggests that the antibiotic resistance genes are key for the bacteria to survive alongside the fungus on the hedgehog’s skin.

“This kind of MRSA likely emerged as a result of a co-evolutionary battle on the skin of hedgehogs,” says Harrison.

By comparing the number of mutations in strains of the bacterium, the team estimate that the mecC-MRSA arose in hedgehogs around 1800 – long before the introduction of methicillin in 1959.

MecC-MRSA can cause infections in people, but these are rare. It is unlikely that humans will pick up MRSA from hedgehogs, because we don’t often interact with them. But mecC-MRSA can pass from hedgehogs to livestock, which are more likely to pass an infection to people.

The findings should underline the need to use antibiotics carefully – even new drugs that might seem to kill many types of bacteria, says Harrison. “Resistance is out there,” he says. “Just because we haven’t seen it in humans, doesn’t mean it doesn’t exist somewhere and can’t end up in humans.”

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