Infection Control & Hospital Epidemiology (2019), 40, 171–177 doi:10.1017/ice.2018.319
Original Article
Molecular analysis of bacterial contamination on stethoscopes in an intensive care unit
Vincent R. Knecht1, John E. McGinniss1, Hari M. Shankar1, Erik L. Clarke2, Brendan J. Kelly3, Ize Imai1, Ayannah S. Fitzgerald1, Kyle Bittinger4,5, Frederic D. Bushman PhD2 and Ronald G. Collman1,2
1Pulmonary, Allergy and Critical Care Division, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, 2Department of Microbiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, 3Division of Infectious Diseases, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, 4Department of Pediatrics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania and 5The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
Abstract
Background: Culture-based studies, which focus on individual organisms, have implicated stethoscopes as potential vectors of nosocomial bacterial transmission. However, the full bacterial communities that contaminate in-use stethoscopes have not been investigated. Methods: We used bacterial 16S rRNA gene deep-sequencing, analysis, and quantification to profile entire bacterial populations on stethoscopes in use in an intensive care unit (ICU), including practitioner stethoscopes, individual-use patient-room stethoscopes, and clean unused individual-use stethoscopes. Two additional sets of practitioner stethoscopes were sampled before and after cleaning using standardized or practitioner-preferred methods. Results: Bacterial contamination levels were highest on practitioner stethoscopes, followed by patient-room stethoscopes, whereas clean stethoscopes were indistinguishable from background controls. Bacterial communities on stethoscopes were complex, and community analysis by weighted UniFrac showed that physician and patient-room stethoscopes were indistinguishable and significantly different from clean stethoscopes and background controls. Genera relevant to healthcare-associated infections (HAIs) were common on practitioner stethoscopes, among which Staphylococcus was ubiquitous and had the highest relative abundance (6.8%–14% of contaminating bacterial sequences). Other HAI-related genera were also widespread although lower in abundance. Cleaning of practitioner stethoscopes resulted in a significant reduction in bacterial contamination levels, but these levels reached those of clean stethoscopes in only a few cases with either standardized or practitioner-preferred methods, and bacterial community composition did not significantly change. Conclusions: Stethoscopes used in an ICU carry bacterial DNA reflecting complex microbial communities that include nosocomially important taxa. Commonly used cleaning practices reduce contamination but are only partially successful at modifying or eliminating these communities.
(Received 1 August 2018; accepted 13 November 2018)
Stethoscopes are frequently used on multiple patients, and they have been implicated as vectors for nosocomial transfer of bacteria responsible for healthcare-associated infections (HAIs). It is well documented that practitioner stethoscopes are not routinely dis- infected,1,2 and studies based on bacterial culture show that they may be contaminated with potential pathogens including methicillin-resistant and -sensitive Staphylococcus spp, multidrug- resistant P. aeruginosa, Acinetobacter spp, Enterococcus spp, Escherichia coli, Klebsiella spp, and Streptococcus spp.3–5 Culture- based studies have also shown that thorough stethoscope decon- tamination can significantly reduce pathogen colony-forming units (CFUs),6,7 although the impact of actual practitioner practices is less clear. Culture-based studies are limited, however, because culture can only identify agents of a priori interest but not entire microbial communities that may be present.
Author for correspondence: Ronald Collman, 522 Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, PA 19104. E-mail:
collmanr@pennmedicine.upenn.edu
Cite this article: Knecht VR, et al. (2019). Molecular analysis of bacterial
contamination on stethoscopes in an intensive care unit. Infection Control & Hospital Epidemiology 2019, 40, 171–177. doi: 10.1017/ice.2018.319
© 2018 by The Society for Healthcare Epidemiology of America. All rights reserved. In contrast to culture, which is focused on individual bacteria
and is only semi-quantitative, emerging molecular approaches using next-generation sequencing can provide unbiased profiling of entire bacterial communities in a manner that is both com- prehensive and highly quantitative.8,9 These powerful approaches have revolutionized studies of the microbiome and of microbial ecology. Here, we used next-generation sequencing to investigate bacterial contamination on several types of stethoscopes in a medical intensive care unit (ICU), including stethoscopes carried by practitioners and used with multiple patients. We also inves- tigated the effects of cleaning protocols that are used by practi- tioners in everyday practice.
Materials and Methods Sample collection method (set A)
Stethoscope samples were collected in the medical ICU at the Hospital of the University of Pennsylvania. Stethoscope dia- phragms were swabbed for 60 seconds using a flocked swab
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