Dirty stethoscopes may be helping to spread dangerous bugs around GP surgeries and hospital wards, a study suggests.

One of the instruments was found to be more contaminated with bacteria than the palm of a doctor’s hand after being used to examine 71 patients.

Among the microbes spreading from patients was the potentially deadly superbug MRSA (methicillin-resistant Staphylococcus aureus).

Dr Didier Pittet, from the World Health Organisation Collaborating Centre on Patient Safety at University of Geneva Hospitals in Switzerland, said: “By considering that stethoscopes are used repeatedly over the course of a day, come directly into contact with patients’ skin, and may harbour several thousands of bacteria (including MRSA) collected during a previous physical examination, we consider them as potentially significant vectors of transmission.

“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.”

Dr Pittet’s team conducted a study in which 71 patients were examined by one of three doctors using sterile gloves and a stethoscope.

After each examination, the tube and diaphragm of the stethoscope and four regions of the physician’s hands were checked for bacteria.

The stethoscope’s diaphragm, the part of the instrument that is pressed onto a patient’s skin, was more heavily contaminated than all regions of the hand except the fingertips.

In addition the stethoscope tube was covered in more bugs than the back of the doctor’s hand.

The study, published in the journal Mayo Clinic Proceedings, is the first to make a direct comparison of bacterial contamination of hands and stethoscopes.