• Bradley W Frazee, Jahan Fahimi, Larry Lambert, and Arun Nagdev.
• Department of Emergency Medicine, Alameda County Medical Center-Highland Campus, Oakland, CA 94602, USA. bradf_98@yahoo.com
• Ann Emerg Med. 2011 Jul 1;58(1):56-63.

Study ObjectiveWe evaluate the frequency of emergency department (ED) ultrasonographic probe contamination and the bacterial species involved and evaluate probe cleaning and disinfection methods.MethodsThis was a 3-part observational cross-sectional study. Surveillance cultures were taken of linear and curvilinear probes on 3 ultrasonographic machines between patient encounters. Cultures of uncovered probes were taken immediately after scanning of skin and soft tissue infections. After experimental probe contamination with methicillin-resistant Staphylococcus aureus (MRSA), we assessed 3-step disinfection by sequential cleaning with a dry towel, saline solution-moistened towel, and quaternary ammonia germicidal wipe and 1-step disinfection by germicidal wipe alone. Cultures were obtained by applying the probe to a blood agar plate.ResultsIn part 1, of 164 surveillance cultures obtained from 6 probes on 29 sampling days during 11 months, 111 (67%; 95% confidence interval [CI] 60% to 74%) grew normal skin flora or environmental flora, 52 had no growth (32%; 95% CI 25% to 39%), and 2 (1.2%; 95% CI 0.3% to 4.3%) grew a clinically important pathogen. In part 2, 14 of 20 (70%; 95% CI 48% to 85%) cultures taken after skin and soft tissue infection scanning produced heavy growth of a clinically important pathogen, including 13 S aureus (5 MRSA). In part 3, cleaning with a dry and moist towel reduced but did not eliminate MRSA. The germicidal wipe step resulted in no growth in 15 of 15 (100%; 95% CI 80% to 100%) cultures in 3-step disinfection and in 9 of 10 (90%; 95% CI 60% to 98%) when used alone.ConclusionSkin and environmental flora are commonly present on ultrasonographic probes between patient encounters in our ED; however, clinically important pathogens are uncommon. S aureus (including MRSA) frequently contaminates uncovered probes during skin and soft tissue infection scanning, but in an experimental model, MRSA appears to be reliably removed by a quaternary ammonia germicidal wipe if the probe is partially cleaned first.Copyright © 2011 American College of Emergency Physicians. Published by Mosby, Inc. All rights reserved.

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