Bacterial Flora of Stethoscopes' Earpieces and Otitis Externa

External otitis caused by Staphylococcus aureus was observed in a nurse after extensive use of a stethoscope. The infection recurred and a similar organism was isolated from the stethoscope's earpiece. The infection did not recur after the earpiece was cleansed after each use. In a prospective study, the bacterial flora of 35 earpieces was evaluated. Fifty-three isolates, 36 aerobic or facultative and 17 anaerobic, were recovered. The number of organisms per earpiece ranged from 14 to 204 (average 92 ± 17). The predominant isolates were Staphylococcus epidermidis (16 isolates), Propionibacterium acnes (12), and S aureus (7). The study demonstrates the colonization of the stethoscope's earpiece with microorganisms that possess the potential for causing nosocomial infection.