Hedgehogs may be adorable, but a new study suggests micro-organisms battling for dominance on their skin led to a strain of antibiotic-resistant bacteria evolving in the 1800s – way before humans even discovered antibiotics.
Methicillin-resistant Staphylococcus aureus (MRSA) is a bacteria variety discovered in 1961 that is resistant to widely-used beta-lactam antibiotics – including their namesake methicillin – making infections harder to treat.
In 2011, a strain of MRSA with a resistance-giving gene called mecC was spotted in cows and humans in Denmark and the UK.
“Using sequencing technology we have traced the genes that give mecC-MRSA its antibiotic resistance all the way back to their first appearance and found they were around in the nineteenth century,” said Dr Ewan Harrison, a senior author of a new study in the journal Nature, in a statement.
“We think MRSA evolved in a battle for survival on the skin of hedgehogs, and subsequently spread to livestock and humans through direct contact,” Harrison explained.
The authors theorize that this battle is between S. Aureus and the fungus Trichophyton erinacei, which can be found on the skin of hedgehogs and naturally secretes two beta-lactam antibiotics. This would have created “a natural selective environment in which methicillin-resistant S. aureus isolates have an advantage,” the authors write, leading to the emergence of MRSA.
The researchers sampled 276 hedgehogs from wildlife rescue centers in Europe and New Zealand. Between 29 and 66 percent of European hedgehogs had mecC-MRSA in their samples, and 6 percent in New Zealand. However, they couldn’t actually collect hedgehog tissue to test for T. erinacei due to “ethical constraints,” so the actual link between this fungus and mecC-MRSA is still unclear.
When the team investigated the evolutionary history of the more successful mecC-MRSA strains in Europe, they noted something surprising: Some lineages “probably originated in the early-to-late 1800s, long before the first [beta]-lactam – penicillin G – became widely available as a therapeutic option in the 1940s.”
Although these results suggest that hedgehogs were the origin of this specific variety of antibiotic-resistant bacteria, this doesn’t mean that humans are off the hook for the dangerous rise in antibiotic resistance – or that we can place all the blame on the spiky little guys.
”It isn’t just hedgehogs that harbour antibiotic-resistant bacteria – all wildlife carries many different types of bacteria, as well as parasites, fungi and viruses,” said Professor Mark Holmes, a senior author of the paper.
This "represents a tiny fraction of the risks compared to overuse of antibiotics in a human medical context" and the risk to human health from mecC-MRSA is "very tiny – almost insignificant," Holmes told the BBC.
Even so, you may want to follow the CDC’s advice, given after an outbreak of Salmonella Typhimurium in 2019, to not “kiss or snuggle hedgehogs, because this can spread Salmonella germs to your face and mouth and make you sick”.
“This study is a stark warning that when we use antibiotics, we have to use them with care. There’s a very big wildlife ‘reservoir’ where antibiotic-resistant bacteria can survive – and from there it’s a short step for them to be picked up by livestock, and then to infect humans,” Holmes continued.