LOS ANGELES — Computer keyboards and keyboard covers harbored vancomycin-resistant Enterococcus faecium and methicillin-resistant Staphylococcus aureus for more than 24 hours, during which time the bacteria easily spread to bare, and in some cases, gloved hands, a Northwestern University study has found.
The findings strongly suggest the need for health care providers to wash their hands after using computers, particularly in hospital settings and around immunocompromised patients, said Gary A. Noskin, M.D., an infectious disease specialist at Northwestern University and director of health care epidemiology and quality at Northwestern Memorial Hospital in Chicago.
Electronic patient records have ushered more computers into examining and patient rooms, heightening the importance of their role as a “viable reservoir for pathogenic bacteria,” in the words of the study presented in poster form at the annual meeting of the Society for Healthcare Epidemiology of America.
Investigators inoculated standard computer keyboards and Dell computer keyboard covers with isolates of vancomycin-resistant E. faecium (VRE), methicillin-resistant S. aureus (MRSA), and Pseudomonas aeruginosa (PSAE).
Samples obtained at various time intervals determined that both VRE and MRSA survived 24 hours, while PSAE was less hardy, growing for 5 minutes on keyboard covers and 1 hour on keyboards.
Bacteria transmission to volunteers' hands increased with the number of times they touched the keyboards. For example, MRSA resulted in recovery of bacteria on hands 92% of the time with 5 touches, versus 42% of the time after 1 touch of the keyboard. Rates for VRE were 50% and 22% after 5 touches and 1 touch, and with PSAE, 18% and 9%, respectively. Bare hands were more likely than were gloved hands to acquire VRE and MRSA, 67% versus 7%, and 80% versus 67%, respectively.
Investigators then conducted an experiment to see whether two quaternary ammonium-based germicides commonly used in health care settings could eliminate bacterial contamination on keyboards and keyboard covers. Virex II 256 (Johnson Wax Professional, Sturtevant, Wisc.), when used as directed with a 10-minute dwell time, successfully disinfected both keyboards and keyboard covers. Sani-Wipes (PDI, Upper Saddle River, N.J.), used as directed with a 5-minute dwell time, disinfected keyboards but failed to eliminate VRE and PSAE on keyboard covers.
Dr. Noskin and his associates recommended hand washing after contact with computers. It is unknown how keyboards and keyboard covers should be disinfected, since there's “just no data” on how frequent germicide use might impact their durability, circuitry, and electronics, he said in a telephone interview following the meeting.