Think your doctor's office is clean? Think again.

A study of stethoscopes found that the instruments were covered with the bacteria Staphylococcus aureus, or MRSA, after a physical exam, MedPage Today reported. The stethoscopes contained more bacteria on the diaphragm, the circular part that touches the skin, than the palm of a doctor's hand.

Researchers from the University of Geneva, who conducted the study, said MRSA was just one type of bacteria that was found on the stethoscopes. The results were published in an issue of the Mayo Clinic Proceedings.

"By considering that stethoscopes are used repeatedly over the course of a day, come directly into contact with patients' skin and may harbor several thousand bacteria (including MRSA) collected during a previous physical examination, we consider them as potentially significant vectors of transmission," said Dr. Didier Pittet, director of the infection control program at the university's hospital who lead the research, according to the BBC.  

More than a month goes by before most stethoscopes are cleaned, MedPage Today reported.

Pittet's team studied bacteria levels on stethoscopes after they had been used by three doctors to examine 71 patients. Researchers also measured how much bacteria was left inside a doctor's hand, fingertips and the back of the hand.

The results showed that the stethoscope contained more bacteria than all of the parts of the doctors' hand. The only exception were the fingertips, which were the most contaminated, the BBC reported.

According to the British Medical Association, there is no evidence of infections stemming from stethoscopes.

But Pittet said doctors should treat stethoscopes like parts of their body that need routine cleaning.

"From infection control and patient safety perspectives, the stethoscope should be regarded as an extension of the physician's hands and be disinfected after every patient contact," Pittet said, the BBC reported.

One doctor, Clare Taylor of the Royal College of General Practitioners, takes cleaning her instruments very seriously.

"I regularly clean my own stethoscope with alcohol wipes and ensure I wash or sanitize my hands after every patient," Taylor said, the BBC reported. "It's part of our role to ensure we do everything we can to prevent the spread of infection."