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Predictors of stethoscope contamination following a standardized physical exam

Introduction / objectives

The relative contribution of stethoscopes in microbial cross-transmission in comparison to the examiners’ hands has not been well described. The aim of this study is to compare stethoscope versus hand contamination following a physical exam and identify predictors of stethoscope contamination.


Following a standardized physical exam using sterile gloves and a sterile stethoscope, bacterial contamination of the following regions were assessed using contact plates: stethoscope diaphragm, stethoscope tube, fingertips, thenar region, hypothenar region and back of physician’s dominant hand. Total aerobic colony count (ACC) were determined on digital photographs using a counting tool.


A total of 56 patients (62% males; median age, 66) were recruited. Median (IQR) contamination (in ACC/25cm2) of examiner’s dominant hand and stethoscope were as follows: fingertips: 835 (IQR, 332-1638), stethoscope diaphragm: 173 (IQR, 36-535), stethoscope tube: 116 (IQR, 34-321), hypothenar region: 16 (IQR, 8-59), thenar region: 15 (IQR, 4-71) and dorsum of hand: 3 (IQR, 1-16). The stethoscope diaphragm and tube were significantly more contaminated than the thenar or hypothenar regions (Wilcoxon ranksum test: p<0.001).There was no difference between the level of tube and diaphragm contamination. Diaphragm contamination was strongly associated with the patient’s level of skin contamination (p<0.001), the patient’s BMI (p=0.01) and the degree of humidity of the patient’s skin (p<0.001).


Our results suggest that stethoscopes’ diaphragm and tube are significantly contaminated following a physical exam and identify predictors of heavy contamination. These findings suggest the need to decontaminate stethoscopes following each use.

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This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Schneider, A., Tschopp, C., Longtin, Y. et al. Predictors of stethoscope contamination following a standardized physical exam. BMC Proc 5 (Suppl 6), P304 (2011).

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  • Public Health
  • Physical Exam
  • Bacterial Contamination
  • Dominant Hand
  • Digital Photograph