December 12, 2018
2 min read

S. aureus found in abundance on ICU stethoscopes

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At minimum, more than half of the stethoscopes sampled at a Philadelphia hospital tested positive for Staphylococcus aureus, and many were also contaminated with Pseudomonas and Acinetobacter bacteria, indicating that the instruments are a potential vector for hospital-acquired infections, researchers reported.

Ronald G. Collman , MD, professor of medicine, pulmonary, allergy and critical care at the University of Pennsylvania Perelman School of Medicine, and colleagues sampled 50 stethoscopes in the medical ICU at the Hospital of the University of Pennsylvania — 20 traditional reusable stethoscopes being carried by practitioners, 20 single-use disposable stethoscopes being used in patient rooms and 10 clean stethescopes straight out of the box.

Staphylococcus was “ubiquitous,” identified on all 40 in-use stethoscopes and in high abundance, representing between 6.8% and 14% of all bacterial sequences, Collman and colleagues reported.

“However, definitive S. aureus assignment was possible for sequences on 24 of 40 practitioner stethoscopes. Therefore, at a minimum, more than half of these stethoscopes were contaminated by S. aureus,” they wrote. “Pseudomonas and Acinetobacter were also widely present,” though in small quantities.

Researchers found that stethoscopes carried in the ICU were contaminated with bacteria.
Source: Adobe Stock

In addition to testing the stethoscopes for bacteria, Collman and colleagues assessed the effectiveness of standard and practitioner-preferred cleaning methods using 30 additional practitioner stethoscopes and found they were only partially successful.

They tested 10 stethoscopes before and after cleaning with a hydrogen peroxide wipe for 60 seconds — the standard method — and allowed the practitioners to use their own preferred method to clean the other 20. Practitioners cleaned their stethoscopes with hydrogen peroxide wipes (n = 14), alcohol swabs (n = 3) or bleach wipes (n = 3) for various lengths of time.

“Cleaning of practitioner stethoscopes resulted in a significant reduction in bacterial contamination levels, but these levels reached those of clean stethoscopes in only a few cases with either standardized or practitioner-preferred methods, and bacterial community composition did not significantly change,” Collman and colleagues wrote.

The researchers were not able to determine if the contaminated stethescopes made any patients sick, or what amount of contamination is clinically relevant for potential transmission, nor were they able to assess isolates for drug resistance or tell if bacteria were dead or alive. They did not test for viral or fungal pathogens.

They suggested that future studies address all these gaps.

“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,” Collman said in a news release. – by Gerard Gallagher


Knecht VR, et al. Infect Control Hosp Epidemiol. 2018;doi:10.1017/ice.2018.319.

Disclosures: The authors report no relevant financial disclosures.