Evaluation of dedicated stethoscopes as a potential source of nosocomial pathogens

Objective: To determine whether the ear tips of dedicated stethoscopes (DS) that are used on patients prescribed contact precautions for methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium, or multiple antibiotic-resistant Acinetobacter baumannii become contaminated with these micro-organisms. Design: Culture of DS ear tips. Setting: A 524-bed tertiary care university hospital. Methods: DS ear tips were inoculated directly onto bacteriologic media and incubated for 48 to 72 hours. Growth of more than 10 colonies from the 2 ear tips collectively was indicative of contamination. Results: Ear tips of 78 DS from 69 patients were cultured. Ear tips from 17 % (13/78) of the DS were contaminated with potentially pathogenic bacteria: 2 with S aureus (1 MRSA), 1 with E faecalis, 7 with Acinetobacter species, 2 with Pseudomonas species, 1 with Escherichia coli, and 1 with Moraxella. None of the stethoscope ear tips was contaminated with the same pathogen for which the patient was prescribed contact precautions (95 % CI, 0-3.8 %). Conclusion: Although the ear tips of DS from patients who were prescribed contact precautions for MRSA, vancomycin-resistant E faecium, or multiple antibiotic-resistant A baumannii were not contaminated with the indicated nosocomial pathogen, 94 % of the evaluable ear tips were contaminated, including with MRSA (1.3 %) and Acinetobacter (11 %). Regular disinfection of ear tips of DS between users should be considered.