Bacterial Sentinels of Noses

Friendly sinus bacteria may keep sinusitis-causing strains in check.

Sep 12, 2012
Ruth Williams

Researchers link a bacteria species, once believed to be innocuous, to chronic sinusitis—persistent inflammation of the sinuses—and also come up with an unusual potential cure. Introducing a second bacterial species into the noses of mice prevented the sinusitis-causing strain from gaining a foothold and causing symptoms. The study, published today (Sept 12) in Science Translational Medicine, suggests that maintaining and augmenting the normal microflora of the nose may be an effective sinusitis treatment.

“This is an extremely interesting result with fascinating potential implications for the treatment of disease,” said Martin Desrosiers, an ear, nose and throat specialist at the Hôpital Hôtel-Dieu in Montréal, Québec, who was not involved in the research. “[It’s]  a radical and exciting idea…[that] gives us new insight into chronic sinusitis,” he said.

Despite sinusitis being one of the commonest afflictions—affecting some 15 percent of the US population annually—little is known about the etiology of the disease. Pathogenic bacterial strains such as Staphylococcus and Streptococcus species—which are known to cause infections of other parts of the respiratory system—have been identified in sinusitis patients and are considered “the usual suspects,” said Susan Lynch, a clinical microbiologist at the University of California, San Francisco.  But, these species have also been detected in the sinuses of healthy individuals, she added. “Just because you find these organisms, it does not mean they are driving disease.”

So Lynch and her colleagues analyzed mucus samples from the sinuses of seven patients who were undergoing surgery for severe chronic sinusitis and seven healthy controls undergoing nose surgery for other reasons. Using a high-throughput microarray screening technique, they found that samples from patients tended to have less diversity of bacterial species than those of healthy controls. Furthermore the relative abundance of certain species differed between patients and controls. Sinusitis patients’s noses were enriched with a skin bacteria called Corynebacterium tuberculostearicum, for example, while samples from healthy controls were enriched with Lactobacillus bacteria, including L. sakei.

Though C. tuberculostearicum “was truly not considered as a pathogen,” said Desrosiers, the results suggest that overabundance of this normally innocuous bug could be the cause of sinus inflammation.

The team confirmed this suspicion in mice, showing that a dose of C. tuberculostearicum delivered into the mice’s nasal cavities caused the animals to develop sinusitis symptoms. A dose of L. sakei, on the other hand, induced no such symptoms. Furthermore, delivering a combination of both L. sakei and C. tuberculostearicum also did not cause sinusitis-like symptoms, suggesting that L. sakei might offer protection against sinus infection. Indeed, in these co-treated mice, the abundance of C. tuberculostearicum dwindled while L. sakei levels remained high. Exactly how L. sakei combats C. tuberculostearicum remains to be tested

“The notion that some bacterial species appear to be protective is something that, in the future, we may be able to use from a therapeutic standpoint, which is of course very exciting,” said Ellen Wald, an expert in pediatric sinusitis at the University of Wisconsin–Madison, who did not participate in the study.

However, seven patients “is an extremely limited data set,” Desrosiers cautioned. “These [results] need to be replicated in other places with more patients prior to their integration into clinical practice.” For one thing, it is possible that a variety of bacterial species could cause sinusitis symptoms, and it is not clear whether L. sakei would be protective in all cases.

Somewhat ironically, Lynch was suffering from a cold and blocked sinuses when talking to The Scientist. Asked whether she was tempted to self-treat with L. sakei, she said only, “the guy who swallowed Helicobactor pylori got a Nobel prize, right? So the stakes are high.”

 

N. A. Abreu et al., “Sinus microbiome diversity depletion and Corynebacterium tuberculostearicum enrichment mediates rhinosinusitis,” Science Translational Medicine, doi: 10.1126/scitranslmed.3003783, 2012.