The stethoscope is one of the most important and perhaps the most recognizable of all tools used by health care professionals. But new research finds they are often crawling with bacteria, including some germs that can cause serious infections.

The study, published in the journal Infection Control & Hospital Epidemiology, found that Staphylococcus, the bacteria responsible for staph infections, was found in abundance on many stethoscopes, with more than half of the devices having confirmed contamination with the bacteria.

Other bacteria that can lead to health care-associated infections, including Pseudomonas and Acinetobacter, were also found on many of the stethoscopes, though in small quantities.

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For the study, researchers used molecular sequencing to analyze stethoscopes in use in an intensive care unit (ICU), including 20 traditional reusable stethoscopes being carried by physicians, nurses and respiratory therapists, and 20 single-patient-use disposable stethoscopes used in patient rooms. They compared these to 10 unused single-use disposable stethoscopes as a control.

All 40 of the stethoscopes in use in the ICU were significantly contaminated with a rich and diverse community of bacteria, the researchers said.

However, it is unknown if the stethoscopes ever made patients sick.

The researchers also found that cleaning stethoscopes using a hydrogen peroxide wipe, alcohol swabs, or bleach wipes reduced the amount of bacteria but did not totally eliminate it.

"This study underscores the importance of adhering to rigorous infection control procedures, including fully adhering to CDC-recommended decontamination procedures between patients, or using single-patient-use stethoscopes kept in each patient's room," senior study author Ronald Collman, MD, a professor of medicine, pulmonary, allergy and critical care at the University of Pennsylvania Perelman School of Medicine, said in a statement.

Collman said future research should focus on improving cleaning methods and studying bacteria on other medical devices used on multiple patients.