[Skip to Content]
Access to paid content on this site is currently suspended due to excessive activity being detected from your IP address 54.197.90.95. Please contact the publisher to request reinstatement.
[Skip to Content Landing]
Article
April 14, 1997

The StethoscopeA Potential Source of Nosocomial Infection?

Author Affiliations

From the Department of Internal Medicine (Drs Marinella and Chenoweth), Division of Clinical Microbiology, Department of Pathology (Dr Pierson), and Division of Infectious Diseases (Dr Chenoweth), University ofMichigan Medical Center, Ann Arbor.

Arch Intern Med. 1997;157(7):786-790. doi:10.1001/archinte.1997.00440280114010
Abstract

Background:  Stethoscope diaphragms have been shown to harbor potentially pathogenic bacteria.

Objectives:  To assess bacterial contamination on the diaphragm and under the plastic rim that secures the diaphragm of stethoscopes of physicians, nurses, medical students, and house staff in an intensive care unit and a general medical ward of a large university hospital. Also to compare the effectiveness of various cleaning agents and assess the transmissibility of bacteria from contaminated stethoscopes to human skin.

Methods:  Aerobic and anaerobic bacterial cultures were performed on 40 randomly selected stethoscopes. We compared the effects of isopropyl alcohol, sodium hypochlorite (bleach), and benzalkonium chloride swabs, as well as soap and water, on reducing bacterial contamination on the stethoscope diaphragm and under the rim. The transmissibility of Micrococcus luteus inoculated onto a stethoscope diaphragm to clean human skin was also determined.

Results:  Eleven genera and species of bacteria were isolated, with coagulase-negative staphylococcus present on 100% of stethoscopes and Staphylococcus aureus on 38%. Clostridium difficile was not isolated. The mean (±SE) number of total colony-forming units was 158± 33 per diaphragm and 289 ±54 per rim. Physicians' stethoscope diaphragms had significantly more colony-forming units of coagulase-negative staphylococci than those of nurses: 163±44 vs 50±12, respectively (P=.02). The most effective cleaning agent was isopropyl alcohol: after cleaning the diaphragm surface, the stethoscope diaphragms contained 0.2±0.2 colony-forming units and the rims contained 2.2±1.5 colony-forming units (P=.01). In addition, M luteus was transferred from inoculated stethoscopes to human skin.

Conclusions:  Most stethoscopes harbor potential pathogens but are not a source of C difficile. Physicians' stethoscopes generally had a higher bacterial load than nurses' stethoscopes. Isopropyl alcohol is an effective cleaning agent when applied to the stethoscope diaphragm. Stethoscopes transfer M luteus to human skin, making it likely that other bacteria can be transferred as well.Arch Intern Med. 1997;157:786-790

×