Skin bacteria can be deadly: genetic changes make germs harmless dangerous

Staphylococcus epidermidis is found on the skin of almost all people – and can sometimes be dangerous.

© University of Bath

There are more microorganisms on and in our bodies than cells – and this microbiome has a significant impact on our health. Even our skin is populated by many invisible roommates such as bacteria. Many of these germs are considered useful or at least harmless. For a long time, this has also been applied to the bacterium Staphylococcus epidermidis.

Recently, however, it became apparent that this supposedly innocent parent of the famous MRSA of the hospital gland could sometimes be fatal. For example, some strains cause life-threatening infections – typically, affected patients who have recently undergone surgery are concerned.

61 striking genes

But why are bacteria on the skin of almost all human beings sometimes the cause of disease? To find out, Sam Sheppard of the University of Bath and his colleagues took a closer look at the germs. They compared bacterial samples of healthy people with microbes on the skin of patients who had an infection after hip or knee surgery.

It turned out that the skin bacteria of sick patients had certain genomic abnormalities, which were mostly absent from the germs of healthy people. Specifically, the researchers identified variants of 61 genes that make apparently innocuous microbes harmless. These genes help the bacteria to multiply in the blood and avoid the body's defenses. In addition, they make the germs resistant to antibiotics, as reported by the team.

Quick spread?

"Staphylococcus epidermidis is a deadly germ that everyone can see but barely notice," says Sheppard. What is dangerous: precisely because bacteria are very common, they can evolve rapidly by exchanging genetic material with each other. "There is therefore a high risk of rapid spread of pathogenic genes, which means that postoperative infections with resistant skin bacteria could become even more common in the future," said the scientist.

To avoid this, he and his colleagues call for more attention to the potentially deadly germ in the future, both in practice and in research. "If we understand who is particularly at risk, we can apply special hygiene measures to these patients, thus minimizing the risk of infection," Sheppard concludes. (Nature Communications, 2018, doi: 10.1038 / s41467-018-07368-7)