Staphylococcus aureus, the bacteria known to cause food poisoning, sepsis and pneumonia, have now been found to hide in deeper parts of the nose than previously believed, according to a Stanford University School of Medicine study.

For the study, the researchers looked into the three different parts inside the nose to determine the presence of S. Aureus - the anterior naris (located near the nostril); the middle meatus (halfway up the nasal cavity) and the sphenoethmoidal recess (located near the roof of the nose and the deepest of the three parts).

Dr. David Relman, M.D., a professor of medicine, microbiology and immunology at the university, examined the nose swabs of 12 healthy people.

They found that if the bacteria exist in the anterior naris, it's also likely to present in the middle meatus and the sphenoethmoidal recess.

"About one-third of all people are persistent S. aureus carriers, another third are occasional carriers and a remaining third don't seem to carry S. aureus at all," Relman said in a statement.

The nose has long been known as the reservoir of S. Aureus. The skin of the groin and armpits are also where the bacteria reside. Normally, the bacteria don't cause any problems. But if it enters the bloodstream, it can cause infections, endocarditis or sepsis.

Even if people try to get rid of it, the bacterium comes back within some time because standard S. aureus-elimination techniques may not reach the far end of the nose. This finding helps answer why techniques used to eliminate the bacteria are not always successful.

In 2011, more than 80,000 severe methicillin-resistant S. aureus infections and more than 11,000 related deaths occurred in the United States.

"Not everyone who carries S. aureus gets sick," Relman said. "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.

"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."

The finding has been published in the journal Cell Host & Microbe.

Topics Bacteria, Stanford University, School of Medicine