Common MRSA germ originates from Europe

Worldwide-wide variant of the resistant pathogen goes back to European ancestors

The methicillin-resistant Staphylococcus aureus (MRSA) is no longer just a hospital germ - variants of the pathogen also appear in everyday life. © Frank DeLeo / NIAID
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European ancestor: The worldwide MRSA germ USA300 has its origin on our continent. Gene comparisons show that the highly contagious resistant bacterium goes back to an ancestor that originated 160 years ago in Central Europe. From there, the germ came to North America at the beginning of the 20th century, continued to develop - and started its triumphal procession around the world.

For a long time antibiotics were considered the most powerful weapon of medicine against bacterial pathogens. But some of these germs are now no longer impressed by any common means: they are largely resistant to it. A particularly dreaded representative of such antibiotic-resistant bacteria is the methicillin-resistant Staphylococcus aureus, MRSA for short.

Formerly infamous only as a hospital germ, since the 1990s, the bacterium has also appeared more and more in everyday life. Often affected whole communities, which are in close contact - for example, residents of a retirement home, sports teams or prison inmates. In principle, however, the germ can nest in any household. Often it is the MRSA type USA300: It triggers skin infections and is easily transmitted.

From North America to Africa

As a highly contagious germ that first appeared in the US 17 years ago and is now widely distributed around the world, USA300 is of great interest to physicians. Where this MRSA variant comes from and where it developed its resistance, however, was previously unknown. Now, a research team led by Lena Strauss from the University Hospital in Münster has set the track of the germ and clarified these questions. The scientists analyzed and compared 224 Staphylococcus aureus samples from 22 countries.

As they report, the gene comparisons point to an origin in Central Europe. Accordingly, USA300 evolved from a less infectious and less resistant ancestor that circulated on our continent some 160 years ago. Around the early 20th century, this ancestor then made it to North America. There, the germ finally acquired the characteristics typical of USA300 and launched its global triumph. display

Thus, the germ of North America came to South America, to the Asia-Pacific region and back to its historical place of origin Europe. That USA300 is widespread in these regions was already known from previous studies. However, the analyzes now reveal that the germ apparently also occurs in Africa, south of the Sahara.

"Foresee future outbreaks"

The results help to better understand the evolutionary history of the highly infectious MRSA bacterium. Thus, the researchers could exclude by their gene comparisons previously traded as a possible USA300 ancestor candidates - including USA500 and a historic MRSA germ from Western Australia. Both bacteria are only remotely related to the currently circulating USA300 strains.

Strauss and her colleagues hope that a look into the past will provide them with advantages for the future: "Understanding the pathways of pathogens is important in order to anticipate and possibly prevent future outbreaks to be able to ", write the scientists. (Proceedings of the National Academy of Sciences Plus, 2017; doi: 10.1073 / pnas.1702472114)

(PNAS, Nov 21, 2017 - DAL)