Among the spines of hedgehogs live bacteria that are resistant to antibiotics. It is a methicillin-resistant strain Staphylococcus aureus, or MRSA. This bacteria is notorious in hospitals because it can make patients very sick and is difficult to combat.
Scientists have always thought that MRSA bacteria evolved in response to the overuse of methicillin in medicine since the 1960s, but it also survives on the backs of hedgehogs in nature. A large international team led by Danish and British biologists has dated the emergence of this resistance at least 200 years ago, long before the discovery of antibiotics. The study was published last week in the magazine temper nature.
Hedgehog bacteria developed their resistance to antibiotics during the so-called “evolutionary arms race”, i.e. competition with fungi that also live among the hedgehogs’ spines. These fungi protect themselves from bacteria by producing two bacteria-inhibiting substances. These are called beta-lactams, and they are a group of antibiotics that also include penicillin, methicillin, and amoxicillin. Hedgehog bacteria did not allow this to happen: they developed resistance to it thanks to natural selection.
There are several strains of MRSA. The hedgehog version owes its resistance to the mecC gene. This codes for an enzyme that binds to beta-lactams and thus blocks its action. This mecC-MRSA is also observed in hospitals and accounts for about 0.5 percent of infections there.
After sifting through genetically methicillin-resistant staph germs from hedgehogs, cattle and humans, the researchers suggest that mecC-MRSA was transferred from hedgehogs to humans via cows. Previous research has shown that different livestock and wild animals can carry mecC-MRSA, but until now it was thought that they would get it from humans and not the other way around. Researchers believe that the majority of MRSA strains originated in humans.
This is an interesting search. So cool to see
Daniel Rosen senior lecturer
“This is very exciting research,” answers Daniel Rosen, Senior Lecturer at Leiden University. He specializes in the evolution and competition of microorganisms, but he did not participate in it himself temper nature-Research. Antibiotic resistance has not often been explored in such detail, and it has been accurately dated. And then also with hedgehogs and cute animals. Not just anywhere in the forest floor. It’s great to see.”
Rosen stresses that this is not the first antibiotic resistance found in nature. It is present everywhere, even far from human influences: in the soil, in caves, in swamps and even in Antarctica. “Microorganisms are everywhere, and everywhere they produce substances with which to defend themselves against other microorganisms.” Resistance is not only related to methicillin and other beta-lactams, but also to a very wide range of substances – and therefore it is not just about bacteria aureus bacteria.
So it is actually a coincidence that this MRSA strain, related to us, apparently appeared around 1800: very recent in evolutionary history. “There are all kinds of lines of antibiotic resistance of bacteria that go back millions of years,” Rosen says. There may be more resistant strains of bacteria that can also infect humans in nature. At least we know that MRSA is found in all kinds of wild animals, including rabbits and birds. But it has now been determined exactly where and when that resistance arose in these hedgehogs, and the direction in which those bacteria jumped to other organisms.”
Meanwhile, researchers around the world are frantically searching for new natural antibiotics using modern genetic techniques. These can help combat MRSA in hospitals. They don’t necessarily have to search for new places, or for new organisms, Rosen says. “It seems that antibiotic production is a matter of turning on certain genes,” he says. Antibiotic genes make up a large part of the genome of many microorganisms, but they are often not used. Microorganisms turn on them only when necessary, often competing with other organisms. We are investigating when and why they do it, and how we can influence it.”
A version of this article also appeared on NRC on the morning of January 14, 2022
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