It is possible that a microbial standoff may have evolved a drug-resistant disease in European hedgehogs long before the age of antibiotics in humans.
A veterinarian at Copenhagen’s Statens Serum Institute, Jesper Larsen, claims that antibiotic use does, in fact, hasten the development of drug resistance in bacteria that live in humans’ bodies. Scientists do not know where most of these genes come from, he says, but the microorganisms must have gotten them from somewhere.
Until now, Larsen and colleagues have been able to trace the evolution of one kind of MRSA to hedgehogs hundreds of years ago. It is possible that the fungus that produces natural antibiotics on these animals’ skin established the conditions for bacterial drug resistance to arise, according to study published in Nature on January 5th.
It is estimated that MRSA infects hundreds of thousands of individuals each year, making it one of the most difficult drug-resistant viruses to cure. The current study focuses on a specific form of MRSA that causes only a small percentage of human illnesses.
When researcher Sophie Rasmussen approached Larsen’s team about collecting a freezer full of dead hedgehogs, the team discovered MRSA in hedgehogs by chance years earlier. Sixty-one percent of the Danish animals tested positive for MRSA. We detected this exceptionally high prevalence in hedgehogs,” Larsen says, implying that the animals were a source of the drug-resistant superbug.
Hedgehogs (Erinaceus europaeus and Erinaceus roumanicus) from ten European countries and Current Zealand were studied in the new study. The noses, skin, and paws of 276 animals were swabbed by workers at wildlife rescue institutions. In the United Kingdom, Scandinavia, and the Czech Republic, MRSA was endemic in hedgehogs.
The researchers detected 16 strains of mecC-MRSA, called after the gene that confers resistance, and mapped the evolutionary links between them by comparing changes across their genetic instruction manuals, or genomes, in the S. aureus. Hedgehog populations have been regularly infected for 130 to 200 years by the three oldest lineages, according to the research, long before penicillin was commercially available in the 1940s. According to the researchers, hedgehogs may be the source of nine of the 16 lineages.
A microbiologist at Statens Serum Institut, Anders Larsen, argues that “there is no doubt that our use of antibiotics drives human pathogens to become resistant to antibiotics,” he adds. There are extremely few cases in which it is possible to pinpoint the source of a problem.
However, this does not explain how the S. aureus in the hedgehogs became resistant to treatment. A fungus called Trichophyton erinacei, which causes human “hedgehog ringworm,” provided a clue to the team’s search in the 1960s. T. erinacei killed some S. aureus, but not those that were resistant to penicillin, according to that study. The researchers found two penicillin-like antibiotics produced by T. erinacei when it was grown in the lab.
Since “they are living cheek by jowl with organisms that produce penicillin,” says Gerry Wright, a biochemist at McMaster University in Hamilton, Canada who was not involved in the study, this discovery shows hedgehogs are a reservoir for MRSA.
According to Wright, the fungus “live in a bad neighborhood.” When competing for resources and a place to call home on the host, they have to contend with other organisms like Staphylococcus aureus.
Wright argues that considering antibiotic resistance in the context of the environment is a must. A natural selection process shapes the evolution of resistance, according to him. Antibiotic resistance can be traced back to prehistoric times, according to Wright’s research. The soil microbiome, or microbial community, has been the primary focus of research in pursuit of this evolutionary change. Yet another potential source for resistance-causing genes and novel antibiotics, he claims, are animals’ microbiomes.
An antimicrobial revolution has taken place in the recent century, and it is followed by microbial resistance to the new medications that are discovered. Wright argues that this is not surprising. Due to the long history of antibiotics and resistance on the planet, he explains. Even if new treatments are discovered, if scientists do not better understand how resistance develops, we will be playing catch-up, he argues.
