Tiny, prickly and cute hedgehogs are helping to defy conventional wisdom about the origins of drug-resistant bacterial infections that kill thousands of people each year.
In a study published Wednesday in natureA group of international scientists has found that the bacteria that cause a difficult-to-treat infection existed in nature long before modern antibiotics began to be mass-produced in the 1940s. Drugs have saved countless lives, but the wide distribution of antibiotics over the decades since has also spurred an evolutionary arms race with the pathogens they target, leading to the emergence of fearsome superbugs that have eluded our efforts to defeat them with drugs.
The key to scientists’ paradigm-shifting theory? Danish road accident.
When researchers examined hundreds of dead hedgehogs from Denmark and other countries in Western Europe, they found MRSA or methicillin-resistant staphylococcus aureus living on the skin of the vast majority of animals. Although MRSA colonizes many mammals, including humans, this was surprising considering the animals were not exposed to penicillin, where they can live harmlessly in the nose or on the skin. The danger arises when these bacteria enter the bloodstream through a wound or intravenous tube, with potentially fatal consequences for those with weakened immune systems.
The scientists were also intrigued by another pathogen they found in many of the same hedgehogs: a skin fungus that produces a penicillin-like substance that inhibits the growth of staphylococcus aureus. Like modern antimicrobials, this naturally occurring antibiotic is in constant battle with the staph bacteria that compete for nutrients on the hedgehog’s skin. The study showed that over time, some of these bacteria developed the ability to outsmart their fungal competitors and thrive in their hedgehog hosts.
What is likely to happen next is a familiar story in the annals of infectious diseases. Special strain of MRSA that colonizes hedgehogs, known as mecC-MRSA later found its way to dairy cows and eventually humans in rural areas where both creatures thrived. In Denmark, mecCMRSA sickens 10 to 30 people a year.
Via genetic coding of hedgehog-derived mecC-MRSA, researchers were able to establish a timeline of its evolution to the early 1800s, long before Alexander Fleming stumbled upon a speck of mold in a petri dish spraying a spreading colony of Staphylococcus.
Anders Rhod Larsen, a microbiologist and lead author of the paper, said the findings add a new wrinkle to the dominant narrative that only the overuse of antibiotics is responsible for the rise of superbugs. D., who directs the National Reference Laboratory for Antimicrobial Resistance at the Statens Serum Institut in Copenhagen. “The main message is that MRSA preceded the use of antibiotics in humans, but the broader theme is that we are not alone in this world,” Larsen said. “Antibiotic resistance has no boundaries and can be transmitted between species.”
Researchers who were not involved in the study said the findings help confirm long-held assumptions about the dynamics of antibiotic resistance. After all, antimicrobial substances are abundant in nature, and bacteria and fungi have long found ways to defeat these compounds.
Lance Price, who leads the Center for Antibiotic Resistance Action at George Washington University, lauded the research for documenting the process in the real world and with such precision.
“This is a very interesting story because who doesn’t love hedgehogs,” he said. “But what’s important about this article is that it demonstrates the natural evolution of a drug-resistant human pathogen.”
Tara C. Smith, an epidemiologist at Kent State University’s College of Public Health who studies livestock-associated MRSA, said the study helps highlight the role animals play as reservoirs of antimicrobial resistance. “It really raises the need for better antibiotic management and paying attention to what we use in both human medicine and animal medicine,” he said.
MRSA infecting hedgehogs did not appear to make them sick, but its overwhelming presence on animals sampled from Denmark largely corresponded with mec.CThe prevalence of MRSA among people in that country. First discovered in 2011, mecC-MRSA has since spread to dairy herds in northern Europe and can sometimes cause infections in cows, but rarely make humans sick.
Jesper Larsen, another lead author of the paper and a senior researcher at the Statens Serum Institute, said the results have already inspired him and other researchers to expand their focus on antibiotic resistance in the wild. But he cautioned against any view that naturally occurring resistance somewhat reduces the urgency of discouraging the use of antimicrobial drugs to treat disease in humans.
“The lesson to be learned here is that when we overuse antibiotics, we are accelerating what is already happening in nature,” he said.
Dr. The study perhaps has another lesson, Larsen added. While the risks for humans to contract MRSA directly from hedgehogs are probably minimal, it has always been prudent to maintain a healthy distance from animals.