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 Saureus (7). The study demonstrates the colonization of the stethoscope's earpiece with microorganisms that possess the potential for causing nosocomial infection.