The Stethoscope— A Vector of Infection?

To the Editor:In the course of investigating a hospital-wide outbreak of methicillin resistant Staphylococcus aureus, 67 physicians' stethoscopes were cultured.Both the bell and the diaphragm were sampled with a sterile cotton swab, and this was immediately streaked onto Columbia Nutrient Agar (BBL), a selective medium for grampositive organisms.The catalase test was used to identify Staphylococcus, and a tube coagulation test served to distinguish between S. aureus and S. epidermidis.Staphylococci were isolated from 63 stethoscopes, and all but one were coagulase negative.The singleS.aureus isolate was methicillin sensitive.Gram-negative bacteria were not sought in our study.Somewhat surprised by the absence of S. aureus from stethoscope cultures, we then pried into physicians' cleaning habits of their stethoscopes.Of 53 physicians surveyed, 34 claimed to clean their stethoscopes with 70% isopropyl alcohol pads.Two physicians also used betadine pads.The frequency of this procedure varied greatly from twice a day to once every six months, but only four physicians cleaned their stethoscopes on a daily basis.Once a month was the preferred interval, followed by once every one or two weeks.