Using Good Skin Bacteria to Fight Eczema

Story by CuriosiTEA JC Team

Original Research Article: Nakatsuji, Hata et al., Nature Medicine, 2021.Journal link: https://doi.org/10.1038/s41591-021-01256-2

Scientists found a friendly type of bacteria on healthy human skin that can fight a harmful germ linked to eczema. The friendly bacteria are called Staphylococcus hominis A9 (ShA9). When the scientists put ShA9 in a lotion and tested it on people with eczema, it was safe and lowered the amount of the harmful germ on eczema skin.

Eczema, also called atopic dermatitis, makes skin red, dry, and itchy. It affects about 15 to 20 out of every 100 kids around the world. Many people with eczema have too much of a germ called Staphylococcus aureus (S. aureus) on their skin. This germ breaks down the skin's protective wall and makes the skin more inflamed. Scientists have tried antibiotics to get rid of it, but they did not work well. Antibiotics can also kill the friendly bacteria along with the harmful ones.

In healthy skin, some friendly bacteria make natural weapons that kill S. aureus. They also block the signals that S. aureuscells send to each other. When the germs can't talk, they don't make the toxins that hurt the skin. But most people with eczema are missing these helpful bacteria on their affected skin. So the scientists asked: can we put the good bacteria back on the skin?

First, the team tested more than 8,000 bacteria collected from healthy skin. They picked ShA9 because it attacked S. aureus but left most other skin bacteria alone. ShA9 was found on about 1 in 5 healthy people, but only on 1 in 100 people with eczema. In mice with eczema-like skin, ShA9 killed 99.6% of the S. aureus. The mice's skin also became less red and inflamed.

Next, the scientists tested ShA9 on 54 adults with eczema. Everyone put lotion on their arms twice a day for one week. 36 people got lotion with ShA9, and 18 got lotion without it. ShA9 was safe, and it lowered the amount of S. aureus on the skin. It did not help everyone's eczema. But it did help the 21 people whose S. aureus could be killed by ShA9. Their skin stayed better for at least four days after they stopped using the lotion.

This study shows that using good bacteria to fight bad bacteria might be a new way to treat eczema. The trial was short and small, and it only included adults. Next, scientists want to test ShA9 for a longer time and in more people, including children. They also want to keep checking that S. aureus does not become resistant to it.

Student Reflection: What surprised us most was that you can put good bacteria right onto the affected skin to fight the bad bacteria. A question we still have is whether ShA9 would stay on the skin and keep working if people used it for months instead of one week. This connects to the real world because many kids have eczema, and a treatment made from bacteria that already live on healthy skin could be a gentler choice than antibiotics or steroid creams.