MRSA occurred 200 years ago in nature long before antibiotics: study

While tracing the genetic history of the bacteria that make up the superbug methicillin-resistant Staphylococcus aureus, commonly known as MRSA, scientists found that it occurred in nature on hedgehogs long before antibiotic use in humans and livestock.

According to a large international collaborative study published in the journal Nature on Wednesday, Staphylococcus aureus first developed resistance to antibiotic methicillin around 200 years ago. Researchers working on a hedgehog survey in Denmark and Sweden discovered that up to 60 per cent of the animals carry a type of MRSA known as mecC-MRSA.

The researchers believe that the antibiotic resistance that developed in Staphyloccocus aureus was an adaptation to having to exist side-by-side on the skin of hedgehogs with a fungus called Trichophyton erinacei, which produces its own antibiotics.

The result is MRSA, and the findings of the hedgehogs’ antibiotic resistance predates antibiotic use in humans and agriculture, the study says.

Due to their antibiotics resistance, MRSA infections are very difficult to treat and the World Health Organization considers them one of greatest threats to human health, according to a release.

MRSA most commonly causes skin infections, and in some cases it can cause pneumonia and other issues. If left untreated, it can become severe and cause sepsis, according to the U.S. Centers for Disease Control (CDC).

Spread of MRSA is usually by contact with an infected person or things that are carrying the bacteria – such as skin-to-skin contact with an infected wound or sharing items like towels or razors.

People with MRSA skin infections usually experience swelling, warmth, redness and pain in the infected area, and it may fill up with pus, the CDC states on its website.

“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 senior study author, Dr. Ewan Harrison, in the release.

“Our study suggests that it wasn’t the use of penicillin that drove the initial emergence of MRSA, it was a natural biological process,” he continued. “We think MRSA evolved in a battle for survival on the skin of hedgehogs, and subsequently spread to livestock and humans through direct contact.”

The new findings contradict most schools of thought, which believe that antibiotic resitance in bacteria causing infections in humans originated from clinical use of antibiotics, the misuse of which is causing the rise of dangerous antibiotic resistance, the study says.

Researchers note that since almost all the antibiotics in use today derive from natural sources, it is likely that resistance to them already exists in nature as well, meaning that it is only a matter of time before overuse causes antibiotics to start to lose their effectiveness.

“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,” said senior study author Mark Holmes, in the release.

Previous work by Holmes first identified mecC-MRSA in human and dairy cows in 2011, which at the time was assumed to have been passed to cows because of the large amounts of antibiotics they are routinely given.

MRSA was first identified in patients in 1960 and approximately 1 in 200 MRSA infections are caused by mecC-MRSA, according to the study. However, the researchers say their findings are not a reason to fear hedgehogs, as humans rarely get infected with mecC-MRSA.

”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,” Holmes said in the release. “Wild animals, livestock and humans are all interconnected: we all share one ecosystem. It isn’t possible to understand the evolution of antibiotic resistance unless you look at the whole system.” 

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