|Year : 2014 | Volume
| Issue : 2 | Page : 156-159
The potential role of stethoscopes as a source of nosocomial infection
Neetu Gupta, Nageswari Gandham, Rabindra Nath Misra, Savita Jadhav, Mahadeo Ujgare, Chanda Vyawahare
Department of Microbiology, Padmashree Dr. D. Y. Patil Medical College, Hospital and Research Centre, Dr. D. Y. Patil Vidyapeeth, Pimpri, Pune, Maharashtra, India
|Date of Web Publication||4-Feb-2014|
Department of Microbiology, Dr. D. Y. Patil Medical College and Research Center, Pimpri - 18, Pune, Maharashtra
Source of Support: None, Conflict of Interest: None
Background: Infectious diseases can be transmitted in various ways . Indirect transmission or vehicle-borne transmission of infection can occur through various agents like instruments, utensils, water, or food. In hospital settings, transmission of infection through contaminated medical devices is always a possibility. Stethoscope is the symbol of health professionals. However, the diaphragm and bells of the stethoscopes have been shown to harbor pathogenic and nonpathogenic microorganisms. Aims: 1) To determine the degree of contamination of stethoscopes used by clinicians and nurses. 2) To identify various microbes from such contaminated stethoscopes and to assess their role as potential pathogens. 3) To determine the effectiveness of 70% ethanol as a disinfecting agent. Materials and Methods: Stethoscopes of 50 healthcare workers from different departments were included in the study. Bacteriological cultures of the samples were done on blood agar and MacConkey agar plates. Organisms were identified by conventional phenotypic methods. Antibiotic sensitivity test (ABST) of the microorganisms was performed by Kirby-Bauer disk diffusion method. Results: Average number of colonies on each stethoscope was 30 . Pathogenic microorganisms including Staphylococcus aureus, Acinetobacter species, Citrobacter species, Pseudomonas stutzeri, Bacillus species, and Aspergillus fumigatus were identified. Among the potential pathogenic organisms, coagulase-negative staphylococci were isolated. Numbers of colonies were highest among the stethoscopes sampled from surgery ward and Medical Intensive Care Unit MICU. Conclusion: Stethoscopes harbor potential pathogens capable of surviving on their surfaces. Despite their best intentions, health professionals can act as a vector for transmission of disease. Disinfecting procedures may be necessary between consecutive patients. Attention to simple preventive strategies can reduce the disease transmission rate.
Keywords: Disinfection, infection, microorganisms, stethoscopes
|How to cite this article:|
Gupta N, Gandham N, Misra RN, Jadhav S, Ujgare M, Vyawahare C. The potential role of stethoscopes as a source of nosocomial infection. Med J DY Patil Univ 2014;7:156-9
|How to cite this URL:|
Gupta N, Gandham N, Misra RN, Jadhav S, Ujgare M, Vyawahare C. The potential role of stethoscopes as a source of nosocomial infection. Med J DY Patil Univ [serial online] 2014 [cited 2019 Jan 16];7:156-9. Available from: http://www.mjdrdypu.org/text.asp?2014/7/2/156/126323
| Introduction|| |
The development of nosocomial infection is a significant problem in each hospital.  Such infections can result due to multiple causes like development and persistence of multidrug resistant (MDR) bacteria, immunocompromised states of patients, and mechanical transmission of agents from one patient to another. Transmission of microorganisms through contaminated medical devices such as electronic thermometers, blood pressure cuffs, stethoscopes, respiratory equipment/devices, gloves, gowns, masks, and white coats, or the skin and nasopharynx of hospital personnel is always a possibility because of their contact with patient bodies. ,,,, Patients with lowered immune system and who have undergone surgical manipulation may develop clinical infection with these microorganisms by "autoinoculation."  Due to their universal use by health professionals, stethoscopes can be a potential source of infection. , Microorganisms can attach and persist on the stethoscopes following their contact with the skin of patients. These microorganisms subsequently may be transferred to other patients where they may colonize and cause infection. Disinfecting stethoscopes before reuse could be useful in reducing the bacterial load and, hence, helps prevent added disease. 
The major objective of this study was to determine whether microorganisms can survive and be isolated from stethoscopes used by clinicians and nurses groups. The second objective was identification of the organisms that might be responsible for spread and colonization in patients. The third objective was to analyze whether or not the degree of colonization could be reduced with use of 70% ethanol.
| Materials and Methods|| |
This prospective study was conducted by the Department of Microbiology in a tertiary care teaching hospital. Fifty stethoscopes of clinicians and nurses groups were examined at their places of use. The diaphragm and bell sections were pressed firmly and rubbed 1 cm on both sides once onto a blood agar and MacConkey agar petri plates of 9 cm diameter. The plates were incubated immediately aerobically at 37°C for 48 h. One of each uninoculated plate was incubated with these as a quality control. The bacterial colonies were then counted and identification of organisms was done by standard conventional methods. Antibiotic sensitivity testing (ABST) of the isolated microorganisms was done by Kirby-Bauer disk diffusion method. In addition, randomly 20 stethoscopes of clinicians and nurses were swabbed once with 70% ethanol, allowed to dry, and then sampled.
| Results|| |
Stethoscopes of 50 health professionals from different hospital wards and intensive care units (ICUs) were included in the study. The pie diagram shown in [Figure 1] gives the department wise distribution of stethoscopes included in the study.
After 48 h of incubation, the bacterial load varied from one stethoscope to the other. The average number of colonies per stethoscope was 30, with a minimum number of 10 colonies from a stethoscope sampled from the Anesthesia Department and a maximum number of 80 colonies seen from one each in surgery ward and MICU.
Fifty-two organisms were identified from 50 stethoscopes. Coagulase-negative staphylococci (CoNS) were the predominant isolates [40 (77%)]. The rest were Acinetobacter species [3 (5%)], Staphylococcus aureus [3 (5%)], Bacillus species [2 (4%)], Aspergillus fumigatus [2 (4%)], Pseudomonas stutzeri [1 (2%)], and Citrobacter koseri [1 (2%)] [Figure 2].
From the 40 isolated CoNS species, 30 (75%) were resistant to amoxicillin and erythromycin. Maximum strains were sensitive to cefoxitin [35 (87.5%)]. [Figure 3] shows the antibiotic susceptibility percentages of CoNS. Among the isolates of three Acinetobacter species, two were from gynecology ward and had the same susceptibility pattern. Sensitivity was seen to imipenem, fosfomycin, and gentamicin, and resistance was seen to ceftazidime, ceftazidime-tazobactam, ceftazidime-clavulanic acid, cefotaxime, and cotrimoxazole. Of the three S. aureus isolated species, two that were isolated from Medical Intensive Care Unit (MICU) were resistant to amoxicillin, erythromycin, cefoxitin, cefuroxime, and clindamycin, and sensitive to only vancomycin. One each of Acinetobacter and S. aureus was isolated from Paediatric Intensive Care Unit (PICU) and both were resistant to all antibiotics tested by disk diffusion method. The organisms P. stutzeri and Citrobacter koseri were sensitive to all the antibiotics tested according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Hence, in this study, 9 of 52 organisms were MDR (isolates resistant to at least one agent in three or more antimicrobial categories).
Cleaning the stethoscopes with 70% ethanol demonstrated a significant decrease in the bacterial count. Out of 20 randomly cleaned stethoscopes, 3 showed colonization with growth of decreased number of colonies (3-5), thus demonstrating the effectiveness of cleaning [Table 1].
| Discussion|| |
Several studies have investigated the presence of microorganisms on stethoscopes as a source of infection, and a brief questioning of practitioners showed that only few of them regularly cleaned their stethoscopes. ,, If stethoscopes are contaminated, it indicates that almost every patient who is examined daily by different physicians and nurses will be exposed to these organisms. Intact skin of patient is an efficient barrier for these microorganisms, but small skin lesions are frequent and accidental blood skin contact may occur. This route of exposure is extremely important when treating patients with wounds, burns, or patients with catheters or tracheostomies, and it should not be underestimated or overlooked.  In this study, most of the stethoscopes showed presence of contamination. The implication of the finding is that stethoscopes could be a vector, playing an important role in the transmission of potential pathogenic microorganisms as well as antibiotic-resistant strains. Cleaning of the heads of stethoscopes between patients could be a means of stopping this. The diaphragm design of many stethoscopes involves a rim that can only be thoroughly cleaned by disassembling the diaphragm which is impractical for regular cleaning. However, simple cleaning would reduce the risk of transmission of microorganisms and prevent the outbreak of infection.  Infection caused by contaminated medical devices could markedly threaten the health of patients, especially those in ICUs, as hospitals now care for far more immunocompromised patients than in previous times.  In our study, the organisms isolated from the ICUs are highly resistant organisms. In most studies, the predominant bacteria isolated from stethoscopes are CoNS. In this study also, isolation of CoNS species was predominant. Different species of CoNS have the ability to acquire multidrug resistance and these species can be extremely virulent for population at risk. Therefore, their antimicrobial resistance pattern is crucial in order to convince the clinicians and other healthcare workers for the necessity of their compliance to health hygiene (cleaning hands, stethoscopes, and other objects). The significant decline in colony count following simple swabbing of the head of stethoscopes with 70% ethanol indicates a solution to this potential danger and is easily available in hospitals. How often a stethoscope must be cleaned is not well established, but there is a correlation between the degree of contamination and frequency of cleaning. Considering the added burden in antibiotic costs and hospital stays which could arise from such infections, infection control programs will definitely be cost effective. However, the implementation of such programs is hindered by poor compliance among doctors, nurses, and other health workers. ,,,
| Conclusion|| |
Our study confirmed that stethoscopes used by healthcare workers were contaminated with pathogenic as well as nonpathogenic microorganisms which could be transmitted to consecutive patients. Apart from diaphragm and bell, an earpiece merits the same attention because of their frequent colonization and poses some risk to stethoscope users also. We recommend strict adherence to disinfection practices by health workers to minimize cross-contamination and ensure patient safety in the hospital.
Some of the measures to prevent cross-contamination would be: Use of 70% ethanol as a disinfectant, disposable stethoscope heads, use of stethoscope sterilizers, and separate stethoscope for each bed. Future research could also focus on designing stethoscopes so as to facilitate de-contamination and on the ways for effective and practicable means of decontamination.
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[Figure 1], [Figure 2], [Figure 3]