About 13 percent of U.S. adults suffered from sinusitis, or sinus infection, in 2010, according to the Centers for Disease Control and Prevention.

But nobody’s quite sure why and how sinuses become infected, a study published Wednesday afternoon notes.

Appearing in the journal Science Translational Medicine, the small but revealing study tallied the various kinds of microbes populating the sinuses of 10 people who had chronic sinusitis and 10 who did not.

The researchers, from the University of California, San Francisco, found that among those with sinus infections, the microbial makeup of the sinuses was way out of whack.

In particular, a species of bacteria called Corynebacterium tuberculostearicum was present in very large numbers. That kind of bacteria is typically found on facial skin and had been thought to be harmless, according to the study.

At the same time, several other kinds of bacteria, including Lactobacillus sakei, were largely absent from the sinuses of those with infections, likely depleted during earlier infections (or perhaps by antibiotic use, though the study didn’t find strong support for that).

Moreover, Lactobacillus sakei was found to be plentiful in the sinuses of those without infections. And in a separate set of experiments, lab mice inoculated with that bacteria gained protection against sinus infections.

That all led the scientists to surmise that Lactobacillus sakei may defend against sinus infections and that, in the bigger picture, sinus infections — and perhaps other kinds of infections as well — may arise from a microbial imbalance that occurs when the depletion of helpful bacteria sets the stage for colonization by harmful bacteria.

Sinus infections, which range in severity from pesky to excruciatingly painful, are usually best left to resolve themselves, which they generally do on their own, eventually. But they’re often treated with antibiotics, which only work when an infection is caused by bacteria, not by a virus. Treating viral infections with antibiotics contributes to the growing problem of antibiotics resistance.

The new findings could eventually lead to a new approach to treating sinusitis and other infections, shifting the focus away from decreasing the population of harmful microbes toward increasing the population of helpful organisms. The study notes that there is precedent for this notion of “restoration ecology,” which, the study says, “Certainly… has proven effective and received much media attention in other host niches such as the lower GI tract where fecal transplant has been shown to resolve recalcitrant Clostridium difficile infection with a high rate of success.”

Do you suffer from sinus infections? What do you usually do about them?

(If you use a neti pot to cleanse your sinuses, please read the FDA’s tips for their safe use. There have been cases of fatal brain infection among people using contaminated water to flush their sinuses.)