Nasal Cavities May Hold Dangerous Bacterial Reservoirs

Researchers at the Stanford University School of Medicine (CA, USA) recruited 12 healthy subjects to assess the biogeography of the nasal microbiota, representing both S. aureus carriers and noncarriers at three nasal sites: the anterior naris, a relatively dry skin-like patch of tissue located near the nostril; the middle meatus, a warmer, wetter, mucus-producing fold found about midway up the nasal cavity; and the sphenoethmoidal recess, situated deep within the nasal cavity near the roof of the nose and, like the middle meatus, warm, wet and mucosal.

The results showed that the presence or absence of S. aureus at one nasal site typically correlated with its presence or absence at the other two, meaning that if the anterior naris is carrying the bacteria, the upper mucosal areas probably are as well. The microbial communities in patients who harbored S. aureus also differed from those in patients who did not, which could mean that that different microbial communities are more or less hospitable to colonization by S. aureus. If this is the case, the researchers argue it may be possible to predict, based on their resident nasal microbes, which patients are most likely to be at high risk of a S. aureus infection, and monitor and treat them accordingly.

A second finding was that in the middle meatus and the sphenoethmoidal recess microbial communities were similar to each another, but quite distinct from the one inhabiting the more accessible and better-studied outer site, the anterior naris. The researchers claim that this suggests that currently routine methods of sampling the nasal cavity for microbe-research purposes may be yielding skewed results.

The researchers also found an inverse relationship between the presence of S. aureus at the three sites and that of a different bacterial species, Corynebacterium pseudodiphtheriticum, suggesting that the two organisms compete with each other and that C. pseudodiphtheriticum—or some molecular product it excretes—may prove useful in countering S. aureus infections. The study was published in the December 2013 issue of Cell Host & Microbe.

“Not everyone who carries S. aureus gets sick. When they're out walking the streets and otherwise healthy, attempts to rid them of their S. aureus are not necessary, and even sometimes futile,” said senior author professor David Relman, MD. “But once a carrier enters a hospital with an underlying illness or a weakened immune system or a high likelihood of undergoing skin-penetrating procedures, S. aureus carriage is a major liability.”

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Stanford University School of Medicine