That bacterial organisms find residence in equipment used by medical men has been known for a long time but this has been investigated only recently. Thermometers, tongue depressors, otoscopes BP cuffs and, particularly, stethoscopes can be carriers of infection.
Studies have been conducted in different countries to detect presence of organisms located in the stethoscope. In some of the studies individual parts of the stethoscope like diaphragm, bell ear piece etc., have been studied.
Incidentally, the unwashed hands of a doctor after examining a patient with a serious infection are a likely source of disease to other patients. Meticulous hand washing in such a situation is the preventive step.
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Surveys conducted in the U.S., Israel, and the Philippines showed that stethoscopes were often contaminated with Staphylococci and were a potential source of hospital-based infections. The studies also showed that frequent cleaning of various parts of the stethoscope decreased the presence of these bacteria. A similar study at Chennai’s Stanley Medical College, in 1980, also threw up similar results.
From skin lesions
The organisms isolated from the stethoscopes were either skin commensals or pathogenic organisms like Staphylococcus aureus, coliform group or Pseudomonas aerugenosa. Interestingly, none of the stethoscopes examined showed enteric pathogens. This is a definite point to the origin of these organisms on to the stethoscopes. Evidently, they originate from superficial skin lesions and some of them may also be among the skin commensals with which the stethoscope is in intimate contact.
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The prevalence of pathogenic organisms was, however, not alarming to warrant special sterilisation techniques for stethoscopes used in the wards. Nevertheless, prolonged use of stethoscopes may diminish the lustre and polish of the diaphragm, thereby making it easier for the microbes to settle in the scratches in the stethoscopes. Frequent changing of the diaphragm may reduce the chances of contamination and thereby minimise the risk of transmission of infection.
Prevention of spread of infection
Cleaning the diaphragm of the stethoscope’s chest piece regularly e.g. at the end of the day and certainly after examining a patient with surface infections like open wounds, burns is advisable. Changing the diaphragm of the stethoscope periodically is also another step.
Meticulous care of the stethoscope — disinfecting it periodically — may prevent drug resistant organisms, e.g. methicllin resistant Staphylococcus, endangering lives of hospitalised patients and even in institutions like schools, soldier’s barracks etc. Medical men owe a duty to their patients in this regard. Particularly, in rapidly spreading epidemic situations like the current “swine flu” the utmost care must be taken by physicians to prevent their equipment like stethoscopes, thermometers etc being vehicles for transmitting the infection.
Dr. V. Kumaraswami, Director in Charge Tuberculosis Research Centre
Prof. S.P. Thyagarajan, Director, Research, Sri Ramachandra University
Prof. K.V. Thiruvengadam, Former Professor of Medicine, Madras Medical College