Hedgehog on a dirt road (archive image)
Photo: Julian Stratenschulte / dpa
Zoonoses - diseases that originally originated in the animal kingdom should be better monitored.
That is one of the very central lessons from the corona pandemic, scientists have called for it several times.
A research team has now shown in a study in the journal Nature that the role of such diseases and germs may have been underestimated for a long time. Accordingly, the notorious hospital germ MRSA probably also comes from the animal kingdom, which is responsible for many deaths. It is one of the antibiotic-resistant bacteria. According to the study, a variant of MRSA (methicillin-resistant Staphylococcus aureus) has been circulating in European hedgehogs since the early 19th century - long before antibiotic pharmaceuticals could have played a role.
In humans, the bacteria generally colonize the nasal mucous membrane and skin, where they are usually harmless. However, if they get inside the body through wounds, for example, they can be dangerous, not only for old and weakened people. Usually such infections are treated with antibiotics, substances from the group of beta-lactams play an important role. However, resistant bacteria such as MRSA are insensitive to almost all beta-lactams. In Europe alone there are around 171,000 MRSA infections per year, writes the team led by Jesper Larsen from the Statens Serum Institute in Copenhagen.
So far, experts have assumed that resistant S. aureus strains arose from the widespread use of antibiotics in medicine. The germ developed resistance to the very first antibiotic, penicillin introduced around 1940. MRSA was first identified in 1960, shortly after the introduction of the antibiotic methicillin in 1959. Since then, numerous MRSA variants have been detected worldwide - both in humans and in animals, especially farm animals such as pigs and cows, which are often treated with antibiotics .
The researchers now examined samples from 276 European hedgehogs from ten European countries and New Zealand.
It was almost exclusively brown-breasted hedgehog (Erinaceus europaeus).
Especially the hedgehogs from Central and Western Europe often carried MRSA, in England and Wales around two thirds of the animals.
Hedgehogs from Mediterranean countries such as Spain, France, Italy or Greece were not infected by such bacteria.
In contrast, MRSA was also found in an animal from New Zealand, where the species was introduced from Great Britain in the late 19th century.
Struggle for survival on hedgehog skin
All affected hedgehogs carried MRSA variants with the mecC gene (mecC-MRSA).
They contain the blueprint for an enzyme that makes bacteria resistant to most beta-lactam antibiotics.
The research team assumes that the resistance in hedgehogs arose as a reaction to the skin fungus Trichophyton erinacei, which is common in the animals.
The scientists found that it produces two beta-lactam antibiotics.
The resistance helps the S. aureus bacterium to assert itself against the fungus on the hedgehog's skin.
"We believe that MRSA developed on the skin of hedgehogs in a struggle for survival and later spread to livestock and humans through direct contact," said co-author Ewan Harrison of Cambridge University in a statement from the university.
The mecC variant of MRSA was originally discovered in dairy cows and then in humans, but also occurs in horses, goats and sheep, as well as wild animals.
The researchers then created a family tree from hundreds of mecC samples from hedgehogs and other animal species.
Based on the mutation rates, they assume that a group of the variant "probably emerged in the early to late 1800s, long before penicillin was widely available as a drug in the 1940s."
The emergence of resistance is therefore not a modern phenomenon that is exclusively related to the use of antibiotics in human and veterinary medicine.
In fact, some mecC-MRSA infections in humans are either due to other intermediate hosts or to direct contact with hedgehogs.
However, the study hardly diminishes the role of antibiotics used by humans in the development of resistance.
According to co-author Karsten Becker, head of the Friedrich Loeffler Institute for Medical Microbiology in Greifswald, the mecC group accounts for less than one percent of the S. aureus colonization in humans in Germany.
"We rarely see mecC-MRSA as an infectious agent in humans," says Guido Werner, head of the National Reference Center (NRZ) for staphylococci and enterococci in Wernigerode and also co-author.
"The majority of the MRSA problem in hospitals is caused by the mecA variant."
In Europe, it is estimated that more than 30,000 people die from antibiotic resistance every year. The authors of the current study emphasize that it is important to closely monitor the development of resistance. The role of natural selection in wild animals as well as the influence of agriculture and medicine have to be taken into account. There are other reservoirs of resistant bacteria in nature, adds the Greifswald expert Becker: "In the Arctic permafrost, viable resistant bacteria have been found in deep layers that have been dormant there for thousands of years."
He also believes that the most comprehensive possible approach to monitoring the development of resistance is necessary.
"This study does not at all diminish the importance of the measures to combat antibiotic resistance," says the microbiologist.
On the contrary: humans use antibiotics en masse: in human and veterinary medicine, in fish farming and in some regions also in plant cultivation.
Such conditions offer advantages for resistant bacteria.
"They can then meet weakened people in hospitals."
joe / dpa
