Stethoscopes loaded with infectious bacteria: Study

Stethoscopes carried by healthcare practitioners are loaded with diverse bacteria, including some that can cause infections, according to a study.

The research, published in the journal Infection Control & Hospital Epidemiology, also reviewed the effectiveness of cleaning methods.

It found a standardised approach to be superior for removing bacteria compared with various approaches employed by health care practitioners.

"This study underscores the importance of adhering to rigorous infection control procedures," said Ronald Collman, a professor at the University of Pennsylvania in the US.

Researchers used molecular sequencing to develop a complete picture of bacteria on stethoscopes in use in an intensive care unit (ICU).

This included 20 traditional reusable stethoscopes being carried by physicians, nurses and respiratory therapists, 20 single-patient-use disposable stethoscopes used in patient rooms, and 10 unused single-use disposable stethoscopes as a control.

The analysis showed all 40 of the stethoscopes in use in the ICU were significantly contaminated with a rich and diverse community of bacteria, including those related to common infections.

However, it could not determine if the stethoscopes ever made patients ill.

Staphylococcus, the bacteria responsible for Staph infections, was found in abundance on all stethoscopes, with more than half of them having confirmed contamination with S aureus.

Other bacteria that can cause healthcare-associated infections, such as Pseudomonas and Acinetobacter, were also widely present on stethoscopes, though in small quantities.

To assess the impact of cleaning on contamination, researchers sampled 10 additional practitioner stethoscopes before and after cleaning for 60 seconds using a hydrogen peroxide wipe.

They also assessed 20 more practitioner stethoscopes before and after cleaning by the practitioner according to their usual method, which included use of alcohol swabs, hydrogen peroxide wipes or bleach wipes used for different durations.

All cleaning methods reduced the amount of bacteria but failed to consistently bring contamination to the level of clean, new stethoscopes.

The standardised cleaning method reduced bacteria on half of the stethoscopes to the clean level, while only 10 per cent, or two of the 20, reached that level when cleaned by the practitioner-preferred method.

This made the stethoscopes as a potential vehicle for transmission of infection.

Molecular sequencing allowed researchers to identify all the types of bacteria and the quantity of bacteria, not just specific pathogens they set out to study.

The DNA test could not distinguish live from dead bacteria, so it is not clear if the stethoscopes are responsible for the spread of disease-causing agents, Collman said.