MRSA bacteria developed on hedgehogs before penicillin was invented

Modern antibiotics were discovered by chance at Alexander Fleming’s lab in 1928, although there have been instances of antibiotic use thousands of years before – from ancient Egyptians who used mouldy bread to treat infected wounds, to German physician Paul Ehrlich who noted it must be possible to kill certain bacteria selectively without harming other cells.

Fleming’s discovery led to “considerable improvements in human and animal health,” a group of international scientists write in a recent issue of the journal Nature. Fleming shared the Nobel prize in Medicine in 1945.

The scientists say that while antibiotic resistance in environmental bacteria is “ancient,” resistance in human pathogens is “thought to be a modern phenomenon that is driven by the clinical use of antibiotics.”

There is a specific kind of methicillin-resistant Staphylococcus aureus bacteria (MRSA) that developed on the skin of hedgehogs as a result of natural evolution. This “notorious human pathogen” appeared in European hedgehogs in the pre-antibiotic era.

The skin of the hedgehog has a fungus, Trichophyton erinacei, that naturally produces antibiotics. Thus, if they are to survive on hedgehog skin, any bacteria must develop antibiotic resistance. The authors say the lineages of the bacteria “spread within the local hedgehog populations and between hedgehogs and secondary hosts, including livestock and humans.”

Thus the researchers point out that natural biological processes, and not antibiotic use in cattle and humans, “drove the emergence of this particular superbug about 200 years ago.”

MecC-MRSA, according to the BBC, constitutes about one in 200 MRSA cases in humans. The researchers emphasise that this is a rare case of an antibiotic-resistant bacteria emerging naturally. The discovery "represents a tiny fraction of the risks compared to overuse of antibiotics in a human medical context", one of the lead researchers, Prof Mark Holmes from the University of Cambridge, tells BBC News.

Veterinary scientists from the University of Cambridge had discovered this particular type of MRSA a decade ago. "We tried to work out how much of a problem it was - so we looked in wildlife and in farm animals and found that it was clearly very widely distributed in nature," Holmes notes. "When we looked at hedgehogs in particular, about half of the animals we sampled had this type of MRSA."

The scientists then honed in on hedgehogs. "We wanted to know," Holmes says, "what's so special about a hedgehog that means there's a lot of these resistant bacteria?"

Research colleagues in Denmark went through more than 1,000 samples of bacteria from wildlife around Europe, and the genetic code-based timeline they built showed that the resistant strain came to being in European hedgehogs in the early 1800s, “long before the clinical use of antibiotics.”

"The fungus growing on the hedgehog was releasing penicillins," Holmes explains.

"The bacteria needed to be resistant because, if you want to live on the hedgehog - where there's a fungus, you have to be resistant to the antibiotics it's producing."

According to the World Health Organization, antibiotic-resistant bacteria is “one of the biggest threats to global health, food security, and development today.” The UN agency warns that “Antibiotic resistance occurs naturally, but misuse of antibiotics in humans and animals is accelerating the process.”

Recommending that people do not use antibiotics unnecessarily or demand them from their health care provider, the WHO reminds us that “Antibiotic resistance leads to longer hospital stays, higher medical costs and increased mortality.”