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  Table of Contents  
Year : 2014  |  Volume : 32  |  Issue : 2  |  Page : 201-202

The prevalence of bacterial contamination of stethoscope diaphragms: A cross sectional study, among health care workers of a tertiary care hospital

Department of Microbiology, St. John's Medical College, Bangalore, Karnataka, India

Date of Submission05-Jun-2013
Date of Acceptance15-Nov-2013
Date of Web Publication2-Apr-2014

Correspondence Address:
S Nagaraj
Department of Microbiology, St. John's Medical College, Bangalore, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0255-0857.129845

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How to cite this article:
Lokkur P P, Nagaraj S. The prevalence of bacterial contamination of stethoscope diaphragms: A cross sectional study, among health care workers of a tertiary care hospital. Indian J Med Microbiol 2014;32:201-2

How to cite this URL:
Lokkur P P, Nagaraj S. The prevalence of bacterial contamination of stethoscope diaphragms: A cross sectional study, among health care workers of a tertiary care hospital. Indian J Med Microbiol [serial online] 2014 [cited 2020 May 29];32:201-2. Available from:

Dear Editor,

The hospital environment has long been known to be one of the most pathologically dense microenvironments. Diaphragms of stethoscopes of doctors, nurses, medical students and other healthcare professionals have been implicated in harbouring a variety of microorganisms. [1],[2],[3],[4]

With the main objective being to ascertain the mean load on the diaphragms and to compare the efficacy of a single alcohol swipe with that of distilled water, on stethoscope diaphragms on a sub-sample of the cohort pre and post-cleaning, we sampled 200 stethoscopes from consenting consultants, post-graduates and interns (total of 170) and those used in the ward (30 numbers). Stethoscopes belonging to doctors who did not use it frequently (i.e. less than three times a day) were not included. The other objectives were to compare the bacterial load on personal stethoscope of doctors (consultants, post-graduates and interns), represented appropriately by stratified random sampling and ward stethoscopes.

Among the 170 stethoscopes of medical faculty, 100 samples were randomly selected for carrying out the comparison of efficacy of alcohol and distilled water. The 100 samples were randomly distributed into two groups of 50 each to test the efficacy of alcohol on one group and that of distilled water on the other group. The same method of cleaning was ensured for both the groups by the same operator. Stethoscope diaphragms were imprinted onto non-selective media (Blood agar), to help grow aerobic bacteria and any fungal pathogens also. Plates were incubated according to standard procedure for 18 hours at 37°C and subsequent growth was identified by standard methods and number of colonies were counted as colony forming units (CFU). [5]

Growth within the impression area was considered as evidence for bacterial contamination and no growth on the area was taken as negative. Growth was quantified as heavy, moderate and scanty depending on the area of the impression-growing colonies. Complete growth within the impression was considered heavy. If colonies could be counted, it was considered as scanty.

Statistical analysis was done using SPSS version 16. Data obtained was not normally distributed; therefore, non-parametric tests were done.

We found that of the 200 stethoscopes sampled, 158 (79%) had evidence of bacteria on the surface of the diaphragms. [Table 1] demonstrates that the reduction of colonies following cleaning either with alcohol or distilled water was significant and that the difference in their efficacy of cleaning was not statistically significant. We also found that all the stethoscopes used in the ward were contaminated and there was no difference in the degree of contamination among the personal stethoscopes of categories of doctors.
Table 1: Effi cacy of alcohol and distilled water after a single swipe

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A study conducted in G B Pant Hospital, Delhi, found that 80% of the stethoscopes grew pathogens; [6] similar results were obtained in our study. In another study conducted in Slovakia, there was significant reduction in bacterial load after disinfection. [7]

We conclude that though stethoscopes are important tools for the doctors and nurses, the potential for contamination with skin flora is high. Cleaning of stethoscopes is not consciously done by the users. In the era of drug-resistant bacteria and the inanimate environment being a major reservoir of these bacteria, importance should be given to cleaning this equipment as they enter the area of a "bed space". Inadequate or no cleaning will help in transmission of bacteria among patients within the hospital. This study demonstrates that a simple swipe with alcohol or distilled water can reduce the contamination. Either of the disinfectants could be used to reduce the bio-burden. Change in attitude towards cleaning of these inanimate objects would help in reducing transmission of organisms within the hospital [Figure 1] and [Figure 2].
Figure 1: Before and after alcohol swipe

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Figure 2: Before and after distilled water swipe

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 ~ References Top

1.Datta P, Rani H, Chander J, Gupta V. Bacterial contamination of mobile phones of health care workers. Indian J Med Microbiol 2009;27:279-81.  Back to cited text no. 1
[PUBMED]  Medknow Journal  
2.Zachary KC, Bayne PS, Morrison VJ, Ford DS, Silver LC, Hooper DC. Contamination of gowns, gloves and stethoscopes with vancomycin-resistant enterococci. Infect Control Hosp Epidemiol 2001;22:560-4.  Back to cited text no. 2
3.Bernard L, Kerveur A, Durand D, Gonot J, Goldstein F, Mainardi JL, et al. Bacterial contamination of hospital physicians' stethoscopes. Infect Control Hosp Epidemiol 1999;20:626-8.  Back to cited text no. 3
4.Madar R, Novakova E, Baska T. The role of non-critical health-care tools in transmission of nosocomial infections. Bratisl Lek Litsey 2005;106:348-50.  Back to cited text no. 4
5.Collee JG. Mackie and McCartney Practical Medical Microbiology. 14 th ed. New York, Churchill Livingstone.  Back to cited text no. 5
6.Sood P, Mishra B, Mandal A. Potential infection hazards of stethoscopes. J Indian Med Assoc 2000;98:368-70.  Back to cited text no. 6
7.Marinella MA, Pierson C, Chenoweth C. The stethoscope: A potential source of nosocomial infection? Arch Intern Med 1997;157:786-90.  Back to cited text no. 7


  [Figure 1], [Figure 2]

  [Table 1]


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