Michael Otto, a Rocky Mountain Labs researcher, led the team that discovered the bacteria - Staphylococcus epidermidis - has an outer covering containing a special protein that allows it to hide from the immune system, wreaking a kind of low-grade infectious havoc.
"It just remains there in relative silence, but it causes typically chronic infections," Otto said. "They just kind of hide there."
Right now, your skin is crawling with S. epidermidis. The generally benign little bug is one of the most common living on the human body, Otto said. But S. epidermidis hardly ever makes people sick.
"If staph epidermidis were virulent, it would not be part of the typical flora," he said. "Otherwise, we'd all be dead."
But it's a different story when S. epidermidis gets on an artificial knee, heart valve or medical catheter and finds itself sewn up deep inside the human body. Then, the bacteria sometimes avoids the immune system and can cause long-term infections. Most of these infections are not deadly, but they can be serious, such as an inflammation of the lining of the heart or toxic infection present all over the body.
That S. epidermidis sometimes wipes off on hospital implants is no surprise, either. The bacteria is so widespread, it ends up on things people touch. But most of the time, it causes no problems.
The protein has an impossible name: poly-gamma-DL-glutamic acid, shortened to PGA. And it's not unique to S. epidermidis, Otto said. The bug behind anthrax travels in a thick coating of the stuff. And other microorganisms, particularly those living in salty environments, also create PGA.
Otto said he thinks its no accident S. epidermis and salt-tolerant microorganism both make PGA.
The skin, which is S. epidermidis' natural home, is also pretty salty.
"It may be just by chance that that PGA works so well" keeping the bug alive when it gets inside the body, he said.
One peculiarity of their findings is the relatively small amount of PGA that seems to be required to allow S. epidermidis to hide.
"We don't know exactly how it works. It seems to work in very low amounts," he said. "We were surprised that such a low level of production resulted in such a significant level of protection."
Whereas the anthrax bug wears a snowsuit of PGA, S. epidermidis needs only a T-shirt of the stuff to avoid being found and snuffed by the body.
Their research started with 2003 publication of the entire genome sequence of S. epidermidis.
"It was quite a surprise at the time," he said, to find the genes for PGA in the mix.
"Our job was to show that these genes were not just junk in there, but to show that are expressed," he said.
Work on the project was an international affair. Two researchers, including Otto, hailed from Germany. One was from China and a third was from Slovakia. Three others came from Montana. The research was conducted at Hamilton.
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