How Neutrophils Kill Superbugs on the Skin

According to a study published today in Cell Reports, neutrophils could be responsible for controlling bacterial numbers of an antibiotic-resistant strain of Staphylococcus aureus (MRSA) on human skin before the bacteria get a chance to invade. The results could provide an explanation for why this superbug is only carried transiently by some people.

In the new study, the researchers developed a “humanized” mouse model in which human skin is grafted onto mice, allowing them to look at the human tissue response in vivo. They found that after the skin had been colonized with MRSA, neutrophils were recruited to the skin, resulting in the antibiotic-resistant bacteria being killed.

“We hope that our humanized skin model will help make sure that our results are relevant to humans, and not just mice,” says senior author Keira Melican of the Karolinska Institutet.

The study also highlights how dynamic the human skin is. The outer layers of the skin were once considered to be a dry, dead wasteland, and a very challenging environment for microbial inhabitants. However, a body of research is now emerging to show that this is not the case.

“The skin is an incredibly dynamic biological environment where immune cells and microbes stand off against one another to maintain some kind of equilibrium—a fraught peace,” says Melican. “Breaks in these equilibria typically lead to bad outcomes for humans, and understanding how this process works on the skin could have an impact on how we prevent and treat skin infection in the future.”

Staphylococcus aureus is a common bacterium carried by up to 50% of the population. However, it is capable of causing some serious infections that are becoming more difficult to treat with the rise of antibiotic resistance. Understanding the human immune response is a critical part of understanding how to curb the spread of resistant bacteria.