Why does staph bacteria cling so tenaciously to human skin?

A new study, co-led by Auburn University’s Department of Physics alongside scientists in Belgium and the United Kingdom, may have uncovered the answer.

Staph uses a protein called SdrD like a grappling hook to attach itself to a human protein called desmoglein-1. The bond withstands forces so powerful that they rival the strength of some chemical bonds, researchers report in Science Advances.

This helps explain why staph bacteria remain attached to the skin even after scratching, washing, or sweating. “It is the strongest non-covalent protein-protein bond ever reported,” says Rafael Bernardi, Associate Professor of Physics at Auburn University in Auburn, AL, and one of the senior authors, in a news release. “This is what makes staph so persistent, and it helps us understand why these infections are so difficult to get rid of.”

Calcium Plays a Key Role

The study also revealed that calcium plays a key role in fortifying this bacterial grip. When calcium levels were reduced in laboratory experiments, the bond between SdrD and desmoglein-1 weakened significantly. When calcium was added back, the bond became even stronger.

This finding is particularly relevant for patients with eczema, where calcium balance in the skin is disrupted. Instead of protecting the skin, these irregular levels may actually make staph’s grip tighter. “We were surprised to see how much calcium contributed to the strength of this interaction,” explains Priscila Gomes, a researcher in Auburn’s Department of Physics and co-author of the study. “It not only stabilized the bacterial protein, it made the whole complex much more resistant to breaking.”

To uncover these details, the team combined single-molecule experiments with advanced computational simulations. Using atomic force microscopy, researchers in Europe measured the force of a single staph bacterium attaching to human skin proteins. Meanwhile, Auburn physicists modeled the interaction atom by atom on powerful supercomputers. The two approaches converged on the same remarkable conclusion: SdrD’s grip on desmoglein-1 is stronger than any other protein bond known in biology.

This discovery may open the door to new strategies for combating antibiotic-resistant infections. Instead of trying to kill bacteria directly, which often drives the evolution of resistance, scientists could design therapies that block or weaken bacterial adhesion. If staph cannot cling to the skin, the immune system has a better chance of clearing it before infection takes hold. “By targeting adhesion, we are looking at a completely different way to fight bacterial infections,” Bernardi says. “We are not trying to destroy the bacteria, but to stop them from latching on in the first place.”