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The stethoscope. A potential source of nosocomial infection?
M A Marinella1, C Pierson, C Chenoweth
1Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, USA.
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.
Insights
Stethoscopes commonly harbor bacteria, with physicians' devices showing higher contamination. Isopropyl alcohol effectively cleans diaphragms, and stethoscopes can transfer bacteria to skin.
Area of Science:
- Microbiology
- Infection Control
- Medical Devices
Background:
- Stethoscope diaphragms are known reservoirs for potentially pathogenic bacteria.
- Understanding stethoscope contamination is crucial for preventing healthcare-associated infections.
Purpose of the Study:
- To assess bacterial contamination on stethoscopes in a hospital setting.
- To compare the efficacy of various cleaning agents.
- To evaluate the transmissibility of bacteria from stethoscopes to human skin.
Main Methods:
- Bacterial cultures were performed on 40 stethoscopes from healthcare professionals.
- Isopropyl alcohol, bleach, benzalkonium chloride, and soap/water were tested as cleaning agents.
- Transfer of Micrococcus luteus from stethoscopes to human skin was assessed.
Main Results:
- Eleven bacterial genera were isolated; coagulase-negative staphylococcus was ubiquitous.
- Physicians' stethoscopes had higher bacterial loads than nurses'.
- Isopropyl alcohol was the most effective cleaning agent, significantly reducing bacterial counts.
Conclusions:
- Stethoscopes frequently harbor pathogens, though not Clostridium difficile.
- Physicians' stethoscopes showed higher bacterial contamination.
- Isopropyl alcohol is recommended for stethoscope diaphragm cleaning.
- Stethoscopes can transfer bacteria to skin, posing a transmission risk.