I think that this sentence is a bit confusing. I don't believe that "shown" means "put on display" in this case. I think it means"demonstrated " or "proven". I believe what the person intended to communicate was the following: "Our study proved that many patients have this microbe on their skin. Nobody had previously proven this."

A kind of microbe was put on display. Now the same microbe has been found on the skin of the patients.