How (and why) to clean a stethoscope

Research has found that stethoscopes harbor microbes and that many clinicians never clean theirs.

Ever wondered how many germs you're wearing around your neck? Studies show that the microbial community on a stethoscope is robust and sometimes includes drug-resistant pathogens like Staphylococcus aureus.

In one recent study, microbe samples taken from stethoscope bells and diaphragms found S. aureus, Acinetobacter, and Klebsiella pneumoniae, according to results published in the January 2019 Journal of Infection Prevention. Out of 62 hospital staff members surveyed as part of the study, 33 (53.2%) said they had never cleaned their stethoscopes.

Image by Getty Images
Image by Getty Images

“This study is from India, but I bet that's probably pretty close to the case in the U.S. The stethoscope is so commonly used, but people just don't think about it,” said Michael B. Edmond, MD, FACP, MPH, MPA, chief quality officer and associate chief medical officer at the University of Iowa Hospitals & Clinics in Iowa City.

Dr. Edmond and other infection control experts explained why stethoscope decontamination is especially important in the hospital and offered tips for spotless stethoscoping.

‘The third hand’

As part of standard precautions, the CDC categorizes stethoscopes as noncritical patient-care items because they only touch intact skin. While this category poses the least risk of infection transmission among clinical equipment, stethoscopes should be cleaned between patients and, if visibly soiled, disinfected with an Environmental Protection Agency-registered hospital agent, the CDC recommends.

The risk of a patient getting sick from a dirty stethoscope hasn't directly been documented, per se, because the bacteria carried by the devices are common and found in many other areas of the health care environment, said Aneesh K. Mehta, MD, an infectious diseases subspecialist and associate professor of medicine at Emory University School of Medicine in Atlanta. “But at least we believe that the theoretical risk is there, and just as we clean our hands, cleaning anything that might contact the patient would be potentially beneficial to the patient,” he said.

Stethoscope hygiene is more important in the hospital than in outpatient practice because hospitalized patients have more risk factors for infection, such as central lines, said Dr. Edmond. “If you're seeing outpatients who are relatively healthy, I think the risk is going to be much less,” he said.

Despite the CDC's recommendations and higher stakes in the hospital, adherence to appropriate stethoscope hygiene remains low. One research letter, which refers to the stethoscope as “the third hand,” found that only about 5% of trainees at three hospitals performed stethoscope hygiene in non-isolation rooms, according to results published in the July 2015 Journal of Hospital Medicine.

With the aim of increasing stethoscope hygiene, another study tested the effect of an educational intervention at the start of clinical rotations for housestaff, medical students, and attendings. Despite receiving a brief PowerPoint presentation, reminders, and access to cleaning supplies, the intervention group still had zero stethoscope hygiene by the end of the quality improvement project, according to results published in the July 2017 American Journal of Infection Control.

“Some may not be aware of guidelines that we clean our stethoscopes in between patients, as this was not something we were originally taught,” said lead author Jürgen L. Holleck, MD, ACP Member, a hospitalist at Veterans Affairs Connecticut Healthcare System in West Haven and assistant professor at Yale University School of Medicine in New Haven. Surveying clinicians on their beliefs around stethoscope hygiene, his group found that forgetfulness, time constraints, and limited access to supplies were perceived barriers.

Overall, stethoscope cleanliness is a habit that is best formed the very first time a medical student sees a patient, said Dr. Edmond, also a clinical professor of infectious diseases at the University of Iowa. Dr. Holleck said that medical students at his institution now receive a checklist when learning the physical exam that includes wiping the stethoscope in addition to performing hand hygiene.

To increase awareness of stethoscope hygiene, Dr. Edmond models the behavior and speaks to residents about infection control, which is particularly salient on the infectious diseases consult service. “It's interesting because if I do it, they'll do it. I don't know how that habit carries over, though, after they move on to their next rotation,” he said. “I don't think most doctors are in the habit of doing it yet.”

Keeping it clean

Establishing the habit may be the trickiest part of stethoscope hygiene, but there's also the challenge of choosing from the wide range of cleaning options. Ultimately, clinicians have their choice, as studies have found that various cleaning techniques, such as alcohol swabs, hydrogen peroxide wipes, and alcohol-based hand sanitizers, all work, said Dr. Holleck, adding that a bleach wipe should be used if there is suspicion of Clostridium difficile.

In one study, researchers asked physicians to clean their hands, then either use alcohol-based hand sanitizer on their palms to clean their stethoscope diaphragms or use alcohol wipes. Overall, both methods were very effective, although the wipes provided a more consistent decrease in bacteria, according to results published in the August 2010 Infection Control & Hospital Epidemiology.

Perhaps more important than effectiveness, however, is whether clinicians perform stethoscope hygiene at all, said Dr. Mehta, lead author of the study. At his hospital, hand sanitizer is generally easier to use, quicker, and more readily available compared to wipes, he said. “We get better compliance, so that is my suggested strategy.”

With hand sanitizer available on the walls outside every patient room, it is easy to remember to perform hand hygiene when entering and to perform both hand and stethoscope hygiene when exiting, Dr. Mehta said. Once Dr. Mehta cleans his hands after a patient encounter, his strategy is to rub the surface of the stethoscope diaphragm (the area of most concern because it touches the patient) for about 30 seconds with either the hand sanitizer or a wipe. “By rubbing it for that amount of time, you can really get the product into all of the areas of the diaphragm and ensure a good amount of contact time,” said Dr. Mehta.

At Dr. Edmond's hospital, there has been a concerted effort to make sure there are disinfectant wipes readily available. “Like anything that we're asking health care workers to do, you have to make it easy for them to actually do it, or your compliance rates will be low,” he said. The wipes contain quaternary ammonium compounds, commonly called “quats,” and do not require gloves to use, as bleach wipes do, Dr. Edmond said.

When using the wipes, wipe them across the entire surface of the stethoscope and then allow it to air dry (which happens quickly), said Dr. Edmond, who prefers the wipes to hand sanitizer because they can cover a larger surface area. “I just wipe down the entire scope and then do the bell, so I find the wipes to be a lot easier to use. . . . Now I'm at a point where when I walk out of the room, if I don't immediately go to get the wipe, I get that feeling of something isn't quite right, like I'm forgetting something,” he said.

In a study of stethoscopes in the ICU, a standardized 60-second cleaning with a hydrogen peroxide wipe got about half of stethoscopes to the level of a brand-new clean stethoscope, while the rest still had considerable reductions in the total amount of bacteria, according to results published in the February 2019 Infection Control & Hospital Epidemiology.

The study authors also asked clinicians to clean the stethoscopes in the usual way that they would between patients. “In that case, a lower proportion achieved the threshold level of a brand-new clean stethoscope,” said senior author Ronald G. Collman, MD, a pulmonology and critical care subspecialist and professor of medicine at the University of Pennsylvania Perelman School of Medicine in Philadelphia.

In the ICU where he works, virtually all patients have an individual stethoscope hanging in their rooms. “We here feel that the single-patient stethoscope is really the best answer” in that setting, said Dr. Collman, who prefers to use hydrogen peroxide wipes for cleaning. However, one downside is that single-patient stethoscopes are not of the same quality as the more expensive ones that individual physicians have attuned their ears to over their careers, he noted.

Overall, although cleaning appears beneficial, physicians and patients should not be panicked about stethoscopes, said Dr. Collman, whose study showed that the overwhelming majority of bacteria on stethoscopes were common oral, skin, and gut bacteria much like those on door handles. “We are always in flux with microbes from people in our environment, so while it is important to apply infection control practices and stethoscope decontamination in settings where particularly dangerous pathogens may be present, I think the notion that we have to fear coming in contact with a stethoscope would be overblown,” he said.