A new study shows that stethoscopes need to be disinfected between patients to prevent contamination inside the healthcare system.

Most people fear the stinging cold of the doctor’s stethoscope against their skin, but a new study from the Mayo Clinic shows that stethoscopes are guilty of more than just a little discomfort.

Testing the bacterial load of stethoscopes in one Swiss university teaching hospital revealed that they were capable of transmitting potentially deadly bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). The bacterium has evolved defenses that are impenetrable by modern antibiotics.

Researchers sampled 489 surfaces—four regions of the doctor’s hand and two sections of the stethoscope—and found contamination of the stethoscope became substantial after only a single physical examination of a patient. They found contamination levels were comparable to that of the doctor’s dominant hand.

“By considering that stethoscopes are used repeatedly over the course of a day, come directly into contact with patients’ skin, and may harbor several thousands of bacteria (including MRSA) collected during a previous physical examination, we consider them as potentially significant vectors of transmission,” the researchers wrote in the study published in the journal Mayo Clinic Proceedings. “Thus, failing to disinfect stethoscopes could constitute a serious patient safety issue akin to omitting hand hygiene.”

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The Mayo Clinic researchers say that because most surveys show that the majority of physicians and nurses do not disinfect their stethoscopes frequently—less than once a month, if ever—practices need to change to prevent contamination between patients.

“Hence, 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. However, the optimal method of disinfection remains to be determined,” the researchers concluded. “Alternatively, cross-transmission could be interrupted by assigning stethoscopes to individual patients. Clearly, there is an urgent need to identify effective transmission mitigation strategies.”

The researchers said that because their study shows strong evidence that stethoscopes are a major contributor to the transmission of microorganisms, common medical devices should be systematically sterilized after each patient.

But because they’re made of metal, rubber, and plastic, further studies are needed to show how they can be effectively disinfected to prevent the spread of disease and infection inside the healthcare system.

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With the rising danger of antibiotic-resistant “super bugs” caused by the overuse of antibiotics, slowing the rate of hospital-acquired infections is a major concern all over the world.

The U.S. Centers for Disease Control and Prevention (CDC) considers reducing hospital-acquired infections as one of its top priorities. A study released in September found that 60 percent of the 80,461 MRSA infections were related to outpatient hospital procedures.

While that number continues drop each year, CDC director Tom Frieden says further reductions are needed because the effectiveness of major surgeries like joint replacements and organ transplants are dependent on a person’s ability to fight off infection.

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