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How many bacteria live on the keyboard of your computer?

      To the Editor:
      The ever-increasing use of computers in all fields of health care has led to several recent studies on the role of keyboard contamination as a vehicle to transmit hospital infections. Fewer studies have been conducted in nonhospital environments,
      • Dogan M.
      • Feyzioglu B.
      • Ozdemir M.
      • Baysal B.
      Investigation of microbial colonization of computer keyboards used inside and outside hospital environments.
      • Anderson G.
      • Palombo E.A.
      Microbial contamination of computer keyboards in a university setting.

      Hirsch S. Germs are working overtime at the office. Los Angeles Times, February 28, 2005. Available at: http://www.latimes.com/2005/feb/28/health/he-germs28. Accessed December 29, 2010.

      • Reynolds K.A.
      • Watt P.M.
      • Boone S.A.
      • Gerba C.P.
      Occurrence of bacteria and biochemical markers on public surfaces.
      where the use of computers is widespread and the same keyboard may be used by several people, thereby becoming a possible vehicle for infection transmission. The fact that many people eat at their workstation also must be considered;

      Hirsch S. Germs are working overtime at the office. Los Angeles Times, February 28, 2005. Available at: http://www.latimes.com/2005/feb/28/health/he-germs28. Accessed December 29, 2010.

      • Collins J.
      Letter from the editor: fighting germs in the workplace.
      crumbs remaining on the keyboard may form a medium favoring the growth of microbes. Keyboard contamination may be viewed as a direct index of hygiene, especially of community hand hygiene, that can be used to plan strategies to promote and improve protection of workers’ health.
      We conducted a study to assess keyboard contamination by common microbes, moulds and yeasts, comparing the results from shared keyboards and nonshared keyboards, and to assess any differences in the entities and types of contamination between keyboards of users who eat at their desks and keyboards of users who do not eat at their desks. We analyzed swabs obtained from the keyboards of 30 computers in use at the University of Siena, 15 not shared and 15 located in computer laboratories used by various students. Swabs of keys were taken. For each key, we tested for a different bacterium among the common bacteria found outside of hospital environments using selective culture medium.
      Typical colonies were counted and typed using the appropriate API galleries. The results were expressed as colony-forming units (CFU) per key. The Mann-Whitney test was used to compare the CFU/key on shared keyboards and nonshared keyboards, and then the CFU/key in users who ate at their desks and those who did not.
      Microbes were recovered at 36°C from all keyboards, with counts ranging from 6 CFU/key to 430 CFU/key. At 22°C, mould was not found on 8 keyboards, but was detected on all other keyboards up to a maximum of 120 CFU/key. Yeast was found on 17 keyboards up to a maximum of 420 CFU/key.
      Staphylococci were found on all keyboards but one at counts up to 120 CFU/key. Typing using API galleries revealed Staphylococcus aureus, S epidermidis, and Micrococcus spp. Enterococcus was found on only 7 keys, including 6 shared keyboards, and was typed as E avium (1-31 CFU/key). Pseudomonas was not detected on any keyboard. S aureus was significantly more common on shared keyboards than on nonshared keyboards (P = .03). Key contamination was significantly greater on the keyboards of users who usually ate at their desks compared with the keyboards of those who did not, and was significant for total microbe load (TML) at 36°C (P = .06) and Enterococcus (P = .037). Bacteria were consistently present on keyboards, but CFU loads on shared keyboards were higher only for Enterococcus.
      Our results are in partial disagreement with those of an Australian study that showed greater contamination of shared keyboards than nonshared keyboards, especially by staphylococci.
      • Anderson G.
      • Palombo E.A.
      Microbial contamination of computer keyboards in a university setting.
      These discrepant results may be related to the fact that the Australian study examined a smaller percentage of nonshared keyboards (14% vs our 50%) or to differences in hygiene habits between Australians and Italians.
      The enterococcus that we found was E avium. This might be due to the fact that there are many pigeons on the balconies and in the courtyards of our universities, where students and employees congregate during breaks. Thus, the type of bacteria found on working equipment provides information about the external environment. This must be borne in mind, especially during “epidemics.”
      Our findings also demonstrate that keyboard contamination can be an indicator of the user’s lifestyle. Indeed, we found greater growth of Staphylococcus and TML on keyboards of users who ate at their desks, probably because crumbs and food residues create an excellent breeding ground for these bacteria.
      • Reynolds K.A.
      • Watt P.M.
      • Boone S.A.
      • Gerba C.P.
      Occurrence of bacteria and biochemical markers on public surfaces.
      If confirmed, this finding suggests that avoiding eating at the workstation or cleaning the desk after eating would be good practice.
      Sources of bacterial contamination can include poor hand hygiene and droplets of saliva

      Marinelli P, Montemarano A, Liguori G, D'Amora M. Hygiene, preventive medicine and public health. Padova: Piccin Nuova Libraria; 2002 (in Italian).

      that inevitably fall on the keyboard during talking, sneezing, and coughing. Thus, to reduce the resident population of microbes with pathogenic potential, it is advisable to observe the general rules of hygiene and to clean keys frequently.
      • Schultz M.
      • Gill J.
      • Zubairi S.
      • Huber R.
      • Gordin F.
      Bacterial contamination of computer keyboards in a teaching hospital.
      To prevent transfer of bacteria to and from keyboards via users’ hands, thorough handwashing before and after keyboard contact is recommended. Handwashing is often considered laborious and is subject to low compliance, as demonstrated by some studies.
      • Wilson A.P.
      • Ostro P.
      • Magnussen M.
      • Cooper B.
      Laboratory and in-use assessment of methicillin-resistant Staphylococcus aureus contamination of ergonomic computer keyboards for ward use.
      • Boyce J.M.
      • Pittet D.
      Guideline for hand hygiene in health care settings. Recommendations of the Healthcare Infection Control Practices Advisory Committee and the HICPAC/SHEA/APIC/IDSA Hand Hygiene Task Force, Society for Healthcare Epidemiology of America/Association for Professionals in Infection Control/Infectious Diseases Society of America.
      Another strategy is to regularly disinfect equipment. Several studies have shown that good hygiene reduces keyboard contamination.
      • Dogan M.
      • Feyzioglu B.
      • Ozdemir M.
      • Baysal B.
      Investigation of microbial colonization of computer keyboards used inside and outside hospital environments.
      • Lu P.L.
      • Siu L.K.
      • Chen T.C.
      • Ma L.
      • Chiang W.G.
      • Chen Y.H.
      • et al.
      Methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii on computer interface surfaces of hospital wards and association with clinical isolates.
      Special reminders have been created to promote regular cleaning of keyboards; this measure promoted 87% compliance in one program.
      • Wilson A.P.
      • Ostro P.
      • Magnussen M.
      • Cooper B.
      Laboratory and in-use assessment of methicillin-resistant Staphylococcus aureus contamination of ergonomic computer keyboards for ward use.

      References

        • Dogan M.
        • Feyzioglu B.
        • Ozdemir M.
        • Baysal B.
        Investigation of microbial colonization of computer keyboards used inside and outside hospital environments.
        Mikrobiyol Bul. 2008; 42 (in Turkish): 331-336
        • Anderson G.
        • Palombo E.A.
        Microbial contamination of computer keyboards in a university setting.
        Am J Infect Control. 2009; 37: 507-509
      1. Hirsch S. Germs are working overtime at the office. Los Angeles Times, February 28, 2005. Available at: http://www.latimes.com/2005/feb/28/health/he-germs28. Accessed December 29, 2010.

        • Reynolds K.A.
        • Watt P.M.
        • Boone S.A.
        • Gerba C.P.
        Occurrence of bacteria and biochemical markers on public surfaces.
        Int J Environ Health Res. 2005; 15: 225-234
        • Collins J.
        Letter from the editor: fighting germs in the workplace.
        Semin Roentgenol. 2007; 42: 1-2
      2. Marinelli P, Montemarano A, Liguori G, D'Amora M. Hygiene, preventive medicine and public health. Padova: Piccin Nuova Libraria; 2002 (in Italian).

        • Schultz M.
        • Gill J.
        • Zubairi S.
        • Huber R.
        • Gordin F.
        Bacterial contamination of computer keyboards in a teaching hospital.
        Infect Control Hosp Epidemiol. 2003; 24: 302-303
        • Wilson A.P.
        • Ostro P.
        • Magnussen M.
        • Cooper B.
        Laboratory and in-use assessment of methicillin-resistant Staphylococcus aureus contamination of ergonomic computer keyboards for ward use.
        Am J Infect Control. 2008; 36: e19-e25
        • Boyce J.M.
        • Pittet D.
        Guideline for hand hygiene in health care settings. Recommendations of the Healthcare Infection Control Practices Advisory Committee and the HICPAC/SHEA/APIC/IDSA Hand Hygiene Task Force, Society for Healthcare Epidemiology of America/Association for Professionals in Infection Control/Infectious Diseases Society of America.
        MMWR Recomm Rep. 2002; 51: 1-45
        • Lu P.L.
        • Siu L.K.
        • Chen T.C.
        • Ma L.
        • Chiang W.G.
        • Chen Y.H.
        • et al.
        Methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii on computer interface surfaces of hospital wards and association with clinical isolates.
        BMC Infect Dis. 2009; 9: 164