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The Germy Stethoscope: Optimizing Sterilization Methods to Stem the Spread of Disease

Stethoscope-SterilizationThe stethoscope, invented in the 1800s and perfected in the twentieth century, is arguably the most important diagnostic tool in the medical field. With it, doctors can detect heart and lung problems before they become life threatening. On the other hand, stethoscopes can harbor bacteria and other microbes that can cause life-threatening diseases. What’s more, these diagnostic tools can become nature’s testbeds, harboring resistant bacteria. Researchers around the world agree: current stethoscope sterilization practices are insufficient, and the hunt for a new, better paradigm is underway.

The Microbe Highway

According to Didier Pittet, M.D., director of the Infection Control Programme at the University of Geneva Hospitals, stethoscopes have the potential to harbor and transmit disease. In fact, recent studies suggest that the diaphragm of a stethoscope can become contaminated with more bacteria than can be found anywhere on the human body. The reason for this lies in the fact that the diaphragm comes in direct contact with the skin of every patient it touches. To prevent the spread of bacteria from patient to patient, doctors must sanitize their stethoscopes between patients. Unfortunately, complete sterilization of a stethoscope requires that the device be placed in a specially-designed steam chamber for several minutes. In emergency rooms, where doctors see patients back to back, this simply is not practical.

In conditions such as these, doctors tend to use alcohol to sanitize stethoscope diaphragms and bells. Alcohol breaks down the proteins of a microbe’s cell walls, essentially melting them. Because bacteria cannot survive this process, the microbes have trouble developing resistance to alcohol. Certain antibiotics, such as Daptomycin, share this property of killing microbes through a direct chemical process. This antibiotic works by binding to a protein that’s found on the cell wall of its victim, essentially unzipping it and causing its organelles to spill out. While bacteria find it difficult to develop resistance to alcohol, some survive the dousing regardless. This is likely because the diaphragm of a stethoscope is porous, and alcohol is a fast-evaporating liquid.

Studies have also shown that the tubes that convey sound to a doctor’s ears can harbor tens of thousands of bacteria as well. Many of these microbes originate   from matter beneath the fingertips of medical personnel.


The potential for doctors and nurses to spread disease via their tools—and even their clothing—is becoming a real concern in an era in which the notion of “superbugs” is frighteningly real. The medical profession has been using modern antibiotics for over 50 years. This time span represents millions of generations of bacterial division, and random mutation allows the possibility that a strain will arise with an inherent resistance to any of the antibiotics we use today. As the resistant bugs supplant the non-resistant strains, more and more patients come into contact with them. Acinetobacter, anthrax, campylobacter, and group-b streptococcus are all believed to have resistant sub-strains. It’s no wonder that man embraced antibiotics; a bacterial infection can be fatal if untreated. However, with the ease at which the stethoscope can act as a means for bugs to jump from one patient to the next, stronger and more convenient means of sterilization are needed.

Optimizing the Sterilization Process

Researchers from Emory University’s Division of Infectious Diseases stated in 2014 that while alcohol only kills around 99% of the bacteria present on a stethoscope’s diaphragm at once, doctors should nevertheless adopt the practice of sanitizing their tools every time they sterilize their hands—which is quite often. The practice could cut down on the transmission of pathogenic bacteria from patient to patient and increase doctor compliance with stethoscope sterilization guidelines.

Currently, those guidelines instruct doctors to sterilize their stethoscopes with alcohol-soaked swabs, but since this task takes up precious time throughout a day, some doctors don’t perform it after each examination, and some forgo the practice altogether. Because the use of liquid alcohol to sanitize stethoscope diaphragms would not require any more time than established hand sterilization practices, the researchers hope that doctors will adopt and practice it consistently.

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