By Eugenia Shmidt, M.D.

You might want to take a deep breath … and hold it. It turns out stethoscopes can carry even more bacteria than most parts of physicians' hands, according to a new study from the University of Geneva.

The results, published Thursday in the journal Mayo Clinic Proceedings, might make patients question exactly where their doctors' stethoscopes have been.

In the study, physicians examined 83 patients using sterile gloves and stethoscopes. After each physical examination, the researchers swabbed various parts of the physician's hands and stethoscopes.

The round part of the stethoscope, which is placed onto the patient's chest (a part known as the diaphragm), contained more bacteria than any region of the physicians' hands except for the fingertips. While the stethoscope tube tended to be more germ-free, it still carried on average more germs than the backs of the doctors' hands.

Not all germs are harmful, of course, so it is likely that a decent portion of the microbes on these doctors' gear were relatively benign.

However, the researchers also looked at the spread of methicillin-resistant Staphylococcus aureus (MRSA) - a potentially nasty bacterial strain that can survive many antibiotics - from patients to doctors' stethoscopes and hands. These germs were transferred from patients to doctors 76 percent of the time - after a single physical examination.

"There are guidelines when and how to clean hands," said lead study researcher Dr. Didier Pittet of the University of Geneva. But, he added, "there are no guidelines telling you when and how to clean stethoscopes."

Pittet said that he hopes that these findings will help doctors be more mindful of their behaviors in the clinical setting that relate to hand hygiene and the use of stethoscopes.

Infectious disease experts not involved with the study, however, said that patients should not worry too much - at least not yet.

"The problem is that it is not clear that this is an important cause of infections with MRSA and does not put it into perspective with the multiple other MRSA sources in and outside the medical environment," said Dr. John Bartlett, former chief of infectious diseases at Johns Hopkins and past president of the Infectious Diseases Society of America.

So what does this mean for patients? According to Dr. William Schaffner, an infectious disease specialist at Vanderbilt University, patients should not hesitate to ask their doctor if he or she disinfected the stethoscope.

"It is a perfectly reasonable thing to inquire about," he said, adding that healthcare professionals should be able to "smile and say, 'Yes, we've done that.'"

Doctor's Take

Stethoscopes are familiar to pretty much anyone who has spent time in a healthcare setting. For doctors, they're virtually an appendage. So it is little surprise that these instruments can harbor a comparable number of bacteria as can be found on hands.

The importance of hand hygiene in the healthcare setting has been proven and universally accepted by the medical community. But according to this study, it may make sense for doctors to put a high priority on "stethoscope hygiene" as well. These findings also raise questions as to whether the medical community should formulate changes that doctors could then universally adopt when it comes to this ubiquitous instrument.

In the meantime, patients should take comfort in the notion that they can work with their doctors to ensure that the stethoscope that presses against their chest is a clean one.