Bacterial Contamination of Keyboards: Efficacy and Functional Impact of Disinfectants

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The increasing use of computers in patient areas has made keyboards important reservoirs for pathogens, possibly contributing to health care-related hospital infections. Current CDC (Centers for Disease Control and Prevention) guidelines for hand hygiene could nullify the risk of transmitting pathogens from computer keyboards to patients, but numerous studies show that fewer than half of health care workers comply with them.

This study examined the efficacy of six disinfectants, three containing quaternary ammonium and one each containing chlorine, alcohol, and phenol, against three microorganisms that were innoculated into computer keyboards. The test organisms were oxacillin-resistant Staphylococcus aureus (ORSA), Pseudomonas aeruginosa, and vancomycin- resistant Enterococcus (VRE) species. Specimens were collected using swabs moistened with trypticase soy broth from 25 computer keyboards in two intensive care units dealing with burns and cardiothoracic disorders, respectively, as well as six nursing units whose patients were receiving short-term care.

All 25 keyboards harbored two or more microorganisms before disinfection. Coagulase-negative staphylococci, diphtheroids, Micrococcus species, and Bacillus species all were found in at least half the keyboards tested. Pathogens recovered from keyboard cultures included ORSA, Vancomycin-susceptible Enterococccus species, Aspergillus flavus, and A. niger. All six disinfectants were very effective in removing or inactivating ORSA, VRE, and P. aeruginosa. A water control also proved to be an excellent means of removing pathogens. In all instances, more than 95% of test bacteria were removed or inactivated. The quaternary ammonium preparations were very active against VRE for the entire 48-hour test period. Alcohol, in contrast, exerted no sustained, clinically relevant activity. The quaternary ammonium compounds also were active for a sustained time against P. aeruginosa, although not as active as against VRE. As was the case for VRE, alcohol was not highly active for a sustained period against P. aeruginosa. Applying disinfectant did not appear to impair keyboard function.

The investigators recommend that computer keyboards used in patient care areas be disinfected each day and whenever visibly soiled or contaminated with blood. Caregivers should avoid touching keyboards with contaminated hands. If keyboard covers are used, they also should be disinfected. Mobile computers used by patients should be disinfected after every session. A keyboard used by an isolated patient should remain in the same room until no longer needed, and then disinfected.

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