Infection Control & Hospital Epidemiology


175


Fig. 4. Quantification of bacterial contamination on practitioner stethoscopes before and after cleaning. Bacterial contamination of practitioner stethoscopes was quantified based on the amount of amplicon following barcoded PCR amplification. Cleaning was done using a standardized (A) or practitioner-preferred method (B). The dashed line indicates the mean bacterial quantification measured on the clean stethoscopes. Both cleaning methods resulted in a significant reduction in bacterial contamination regardless of cleaning method (A: P=5.69 × 10− 5;B: P=.00174; Student t test). In the standardized cleaning group, 5 of 10 stethoscopes fell below the level of the clean stethoscopes as determined by amplicon concentration. In the practitioner-preferred cleaning group, 2 of 10 stethoscopes fell below the level of clean stethoscopes.


Fig. 5. PCoA of bacterial communities on ICU stethoscopes before and after practitioner cleaning. Stethoscopes bacterial communities before and after practitioner cleaning, along with clean stethoscopes and background controls, were analyzed using unweighted (A) and weighted (B) UniFrac and visualized by PCoA. All groups were significantly different in the unweighted UniFrac (P<.05; PERMANOVA), whereas by weighted UniFrac the pre- and post-cleaned stethoscopes types were not different.


V1V2 sequences, although the V4 region detected a somewhat higher prevalence of Burkholderia and Clostridium and somewhat less Stenotrophomonas. For each of these genera, we calculated the relative abundance


(ie, proportion of all bacterial sequences in a sample that were assigned to that genus) across all stethoscopes. Staphylococcus was present at 6.8%–14% relative abundance in the 2 practitioner stethoscope sets based on V1V2 and V4 sequences. Pseudomonas and Acinetobacter were less abundant and were present at slightly greater than 1% based on V4 sequences and ~10-fold lower based on V1V2 sequences, whereas other genera were below 1% in abundance. Thus, practitioner stethoscopes that are used on multiple patients carry sequences of genera that include impor- tant nosocomial pathogens.


Discussion


This study is the first to apply comprehensive molecular profiling to understand stethoscope contamination in a healthcare setting. We found that stethoscopes carried by practitioners in an ICU,


which are used on multiple patients, are significantly con- taminated with a rich and diverse community of bacteria that includes genera associated with HAIs. We also examined the impact of cleaning and found a surprisingly modest effect on contaminating bacterial communities. Taxa of skin, gut and oral sources dominated stethoscope


bacterial communities, and genera associated with nosocomial infection were common. Staphylococcus was not only ubiquitous (found on 40 of 40 stethoscopes tested) but was also present at high abundance, representing 6.8%–14% of all bacterial sequen- ces, depending on stethoscope set and target region queried. Most OTUs could not be assigned at the species level with either V1V2 or V4 sequences. However, definitive S. aureus assignment was possible for sequences on 24 of 40 practitioner stethoscopes. Therefore, at a minimum, more than half of these stethoscopes were contaminated by S. aureus. Pseudomonas and Acinetobacter were also widely present, with the exact frequency and relative abundance differing depending on the 16S variable region sequenced. Different 16S primer sets can have biases in the effi- ciency of detecting specific sequences,19,20 and our findings using


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