Loss of normal microbial diversity may be culprit behind chronic sinusitis

Published on September 13, 2012 at 4:17 AM · No Comments

A common bacteria ever-present on the human skin and previously considered harmless, may, in fact, be the culprit behind chronic sinusitis, a painful, recurring swelling of the sinuses that strikes more than one in ten Americans each year, according to a study by scientists at the University of California, San Francisco.

The team reports this week in the journal Science Translational Medicine that sinusitis may be linked to the loss of normal microbial diversity within the sinuses following an infection and the subsequent colonization of the sinuses by the culprit bacterium, which is called Corynebacterium tuberculostearicum.

In their study, the researchers compared the microbial communities in samples from the sinuses of 10 patients with sinusitis and from 10 healthy people, and showed that the sinusitis patients lacked a slew of bacteria that were present in the healthy individuals. The patients also had large increases in the amount of Corynebacterium tuberculostearicum in their sinuses, which are located in the forehead, cheeks and eyes.

The team also identified a common bacterium found within the sinuses of healthy people called Lactobacillus sakei that seems to help the body naturally ward off sinusitis. In laboratory experiments, inoculating mice with this one bacterium defended them against the condition.

"Presumably these are sinus-protective species," said Susan Lynch, PhD, an associate professor of medicine and director of the Colitis and Crohn's Disease Microbiome Research Core at UCSF.

What it all suggests, she added, is that the sinuses are home to a diverse "microbiome" that includes protective bacteria. These "microbial shields" are lost during chronic sinusitis, she said, and restoring the natural microbial ecology may be a way of mitigating this common condition.

A Painful, Costly Condition

Sinuses are air-filled cavities in the front of the skull that connect to the nasal passages and are lined with mucosal surfaces. They are somewhat shrouded in mystery. Scientists are not entirely sure what they do. They may exist to heat air as it passes into the body, they may be associated with the immune system, or as Lynch and her colleagues speculate, they may represent a site of microbial surveillance just inside the nose where the body can sample bacteria and other microbes entering the body.

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