This study looked at stethoscope bacterial contamination and compared it with hand contamination after a single patient contact.
Stethoscope diaphragm contamination was found to exceed contamination of all parts of the hand except for the fingertips.
The authors recommend cleaning the stethoscope after every patient exam. This should be common sense, but system improvements (like hand washing, as important as that is) tend to become substitutes for common sense. As a result we've all but ignored stethoscope cleaning.
I have another suggestion. By all means use the stethoscope (and clean it after you use it) if you intend, and have the skill, to use it as a meaningful clinical tool. Do not use it merely as a coding enhancer.
Via Hospital Medicine Virtual Journal Club.