Stethoscope Cleaning Standards May Not Eliminate Bacterial Contamination

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In-hospital stethoscope cleaning practices may only be partially effective at eliminating bacterial DNA.
In-hospital stethoscope cleaning practices may only be partially effective at eliminating bacterial DNA.

Per study data published in Infection Control & Hospital Epidemiology, in-hospital stethoscope cleaning practices may only be partially effective at eliminating bacterial DNA.

Investigators conducted 16S rRNA gene deep-sequencing analysis on stethoscope samples collected from the medical intensive care unit at the hospital at the University of Pennsylvania. To obtain bacterial samples, stethoscope diaphragms were swabbed for 60 seconds, using a flocked swab.

Sample Set A comprised 10 clean single-use disposable stethoscopes, 20 in-use disposable stethoscopes for patient rooms, and 20 stethoscopes being carried by physicians, nurses, and respiratory therapists. Clean flocked swabs were also analyzed as background controls. Sample Set B included 10 additional samples collected from practitioner stethoscopes after a "standardized" cleaning with hydrogen peroxide wipes. For Set C, 20 practitioners were asked to clean their stethoscopes using their "preferred" method. Practitioners used hydrogen peroxide wipes (n=14), alcohol swabs (n=3), or bleach wipes (n=3) during the cleaning process. Pairwise Wilcoxon rank-sum tests were performed to examine between-group differences in stethoscope cleanliness trends.

Practitioner stethoscopes had significantly higher 16S amplicon concentration compared with both patient room (P =.035) and clean (P =.004) stethoscopes. Patient room stethoscopes also had significantly higher amplicon concentrations than clean stethoscopes (P = .000018). Clean single-use stethoscopes were indistinguishable from background controls. Bacterial communities observed on stethoscopes were complex, with microbial communities including taxa associated with healthcare-associated infections. Healthcare-associated infection-related genera were common on practitioner stethoscopes, with Staphylococcus in the highest relative abundance (6.8%-14% of contaminating bacterial sequences).

Physician and patient room stethoscopes were "indistinguishable" from one another, although both were significantly different from clean stethoscopes and from background controls. Cleaning of practitioner stethoscopes reduced bacterial contamination levels, but these levels reached those of clean stethoscopes in just 5/20 and 2/20 stethoscopes cleaned by the standardized or practitioner methods, respectively. Cleaning also did not significantly change the bacterial community composition.

These data suggest that existing stethoscope cleaning procedures may be insufficient in eliminating bacterial contamination. Given the abundance of healthcare-associated infection-associated genera on tested samples, researchers recommended further research at additional intensive care units and hospitals to clarify the scope of the issue. Stethoscope use is ubiquitous in medical care; it is essential that such tools remain sterile.

Reference

Knecht VR, McGinniss JE, Shankar HM, et al. Molecular analysis of bacterial contamination on stethoscopes in an intensive care unit [published online December 12, 2018]. Infect Control Hosp Epidemiol. doi: 10.1017/ice.2018.319

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