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Three Part Question

In [Emergency care providers] does [routine cleaning of stethoscopes] reduce [bacterial contamination with MRSA]?

Clinical Scenario

You are evaluating an immunosuppressed patient in the emergency department. As you auscultate his chest, you wonder if your stethoscope could present a significant source of MRSA contamination

Search Strategy

Medline 1950 to October week 3 2007 and Embase 1980 to 2007 week 43 using the OVID interface and Multifile Searching
The Cochrane Library, Issue 4, 2007.
Medline/Embase: (exp stethoscopes/or stethoscop$.mp) AND (exp Staphylococcus aureus/or staphylococcus aureus.mp or MRSA.mp.). LIMIT to English.
Cochrane: stethoscopes.ti.ab.kw.

Search Outcome

A total of 30 papers were found, of which five were relevant

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Cohen H 1997 USA	Stethoscopes (55) and otoscopes of pediatric physicians in community clinics.	Survey	Bacterial contamination	Staphylococcus species isolated from 85.4%; 54% was Staph aureus, 7.3% MRSA	Study group was pediatricians in an outpatient clinic setting. The study initially had 42 stethoscopes, then added an additional 8, not sure how they chose these and why they added them.
			Bacterial contamination after cleaning with alcohol wipe	Colony count reduced by 96.3%
Jones JS 1995 USA	Emergency care providers' stethoscopes (physicians, nurses, and prehospital). 150 total.	Survey	Staphylococcus carriage	89% grew Staphylococcus species, 19% Staph aureus.	Did not address MRSA (possibly because it was published in 1995). The interviewer was a physician, which may have influenced answer of nurses and prehospital personnel.
			CFU reduction after various cleaning methods	94% reduction with alcohol swab, 88% with nonionic detergent, 75% with antiseptic soap.
			Cleansing routine and CFU count	CFUs markedly increased when cleaned less frequently.
Marinella MA 1997 USA	Stethoscopes (47) of medical ICU and general medical ward including physicians, nurses, medical students and house staff.	Survey	Staphylococcal contamination of diaphram	87.5% Staphylococcus coag neg, 27.5% Staph aureus. Nurse's stethoscopes significantly less contaminated.	The study did not address MRSA. Small study size (47 stethoscopes). Study participants not from emergency department and their conclusion must be extrapolated.
			Cleansing agents	Isopropyl alcohol most effective.
			Transmission of Micrococcus luteus to human skin	Human skin was inoculated after contact with a contaminated stethoscope, clinical relevance uncertain.
Nunez et al, 2000, Spain	Stethoscopes (122) from ED clinicians	Survey	Bacterial contamination	S epidermides 97%,
			Bacterial contamination after cleaning	Number of contaminated stethoscopes reduced by 70%
Barrio Torres et al, 2003, Spain	Stethescopes (73) from ED, paediatric and ICU clinicians	Survey	Bacterial contamination	62.23 cfu general, 9.19 cfu S aureus	Results given as average colony forming units
			Bacterial contamination after cleaning	7.45 cfu general, 0.6 cfu S aureus

Comment(s)

A number of surveys have shown general contamination of stethoscopes and have demonstrated that cleaning with isopropyl alcohol reduces this contamination. No direct evidence is presented that links contamination to cross-infection.

Editor Comment

cfu, colony-forming units; MRSA, methicillin-resistant Staphylococcus aureus.

Clinical Bottom Line

Routine cleansing of stethoscopes significantly decreases bacterial contamination.

References

1. Cohen HA, Amir J, Matalon A, et al. Stethoscopes and otoscopes - a potential vector of infection? Family Practice 1997; 14 (6):446-449.
2. Jones JS, Hoerle D, Riekse R. Stethoscopes: A potential vector of infection? Ann Emerg Med 1995; 26 (3):296-299.
3. Marinella MA, Pierson C, Chenoweth C. The stethoscope. A potential source of nosocomial infection? Arch Intern Med 1997;157 (7): 786-790.
4. Nunez S, Moreno A, Green K, et al. The stethoscope in the emergency department: a vector of infection. Epidemiol Infect 2000; 124: 233–7.
5. Barrio Torres J, Pinto Fuentes I, Paez Pena M, et al. El estetoscopio: un potencial vector de infeccion. Pediatrika 2003; 23: 335–40.