Bacterial contamination of computer keyboards and mice – Full Length Research

Infection Research for Computer Keyboards and Input Devices
March 7, 2019
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This study aims at investigating the status of bacterial contamination of four daily used objects, computer keyboards, computer mice, elevator buttons and shopping carts handles. A total of 400 samples were collected from 4 different objects; 100 from each. Samples were collected from different places (offices, internet cafes, homes, buildings and supermarkets) in the city of Jeddah, Saudi Arabia. 95.5% of the total samples collected were contaminated with mixed bacterial growth. Coagulase- negative staphylococci dominated the isolates. The second most common bacterial growth in all specimens was Gram-positive bacilli. Potential pathogens isolated from all specimens were: Staphylococcus aureus, Pseudomonas spp. and Gram negative bacilli. Results indicate that internet café computer keyboards and mice showed 100% contamination in comparison with other objects. The presence of pathogenic and commensal bacteria on the four objects indicates that they might act as environmental vehicles for the transmission of potentially pathogenic bacteria. Key words: Bacterial contamination, computers, public surfaces.
INTRODUCTION Most people do not realize that microbes are found on many common objects outdoors, in their offices, and even in their homes. Such objects include; playground equipments, ATM keyboards, kitchen sinks, office desks, computer keyboards, escalator handrails, elevator buttons and with the spread of supermarkets and hypermarkets the shopping carts handles. All of the latter objects are places that are most touched by the bare hands of people who are in various hygienic conditions. People believe that microbes are only present in research labs or in hospitals and clinics and thus they have a misleading feeling of security in other places. Lack of knowledge about where germs prowl could be the cause of health problems. In fact 80% of infections are spread through hand contact with hands or other objects (Reynolds et al., 2005). Reynolds et al. (2005) used an invisible fluorescent tracer for artificial contamination of public surfaces, they found that contamination from outside surfaces was transferred to 86% of exposed individual's hands and 82% tracked the tracer to their home or personal belongings hours later (Reynolds et al., 2005). The viability of Gram-positive and some Gram- negative organisms under various environmental condi- tions have been described (Noskin et al., 1995). Some microbes are infectious at very low doses and can survive for hours to weeks on nonporous surfaces, such as countertops and telephone hand pieces (Reynolds et al., 2005). Enterococci have been found to survive in dry conditions and on various fabrics utilized in the health care environment. Infectious doses of pathogens may be transferred to the mouth after handling an everyday contaminated household object (Rusin et al., 2002). Recently Ulger et al. (2009) have demonstrated that health care workers' hands and mobile phones were contaminated with various types of microorganisms and concluded that mobile phones used in daily practice may be a source of nosocomial infections in hospitals. Scientific information about the occurrence of bacteria on various objects outside the health care facilities is very little and needs to be enriched in order to educate people on the necessity of improving the habit of hand washing to reduce microbial transmission. The aim of this study was is to investigate the presence of bacteria on 4 different objects (computer keyboards and computer mice, elevator buttons and shopping carts handles) that are frequently used by people in the city of Jeddah, Saudi Arabia.
MATERIALS AND METHODS A total of 400 samples (100 computer keyboards (CK), 100 computer mice (CM), 100 shopping carts (Shc) and 100 elevator buttons (EB) were collected from different places of Jeddah, Saudi Arabia (Table 1) using sterile swabs. 30 control samples from brand new untouched computer keyboards and computer mice were also included. Isolation of various bacterial contaminants from the four different objects (CK, CM, Shc and EB) was performed through standard techniques described by Cheesbrough (2006). Briefly, sterile water- moistened swabs were wiped firmly over the entire surface of the specific object. Each swab was placed in 2 ml of brain heart infusion broth in a sterile container, and vortexed for one minute. Total amount of 100 μl was plated out on each of blood agar and MacConkey agar. All samples were plated within three hours of collection. The pairs of inoculated media were incubated aerobically at 37°C for 24 h. Pure colonies of isolates were identified and characterized using standard microbiological techniques between computer keyboards, mice, shopping cart handles and elevator buttons. All tested surfaces were found to be contaminated with mixed growth. Gram +ve and G-ve pathogenic and non-pathogenic bacteria were isolated. The distribution of isolates on different surfaces was similar (Figure 1). Qualitative bacterial analysis of the isolates on the four different objects revealed that CoN-Staphylococci followed by Gram +ve bacilli were the most common isolates (Table 2). The previous results are expected due to the common vehicle of microbial transmission which is the human hands and fingers. Scott and Bloomfield (2008) suggested that, where conta- minated surfaces come into even relatively brief contact with the fingers or an inanimate surface, a significant number of organisms can be transferred which can be recoverable onto an agar surface. In our study Gram +ve bacteria were more frequently isolated from all surfaces compared to Gram -ve (Figure 1). This could be in part due to the fact that survival of Gram +ve species on laminate surfaces is greater than that of Gram negative organisms (Scott and Bloomfield, 2008). However, both Gram +ve and Gram -ve bacteria have been shown to have similar transfer rates from laminate surfaces to fingertips (Scott and Bloomfield, 2008). Normal skin is inhabited with two categories of bacteria: transient and resident. Resident flora, which are attached to deeper layers of the skin, are more resistant to removal by routine washing. Coagulase-negative staphylococci and Gram +ve diphtheroids are members of this group (Boyce and Pittet, 2002). On the other hand, transient flora colonizes the superficial layers of the skin, and is more amenable to removal by routine hand washing (Boyce and Pittet, 2002). Domestic and public computer key boards and mice were swabbed and cultured. The swabbed areas were the keys mostly pressed like the space bar, the Enter and Backspace buttons. 100% of Internet café's computers were found to be contaminated (Table 1). Comparing these results to the home computer keyboards and mice there is a reduction in the percentage of contamination to 88 and 91% respectively. This reduction is expected due to the limited number of users and assumed continuous cleaning in houses. Nevertheless a percentage of 88 or 91% is still considered high. Percentage of contamination of offices’ computer keyboards and mice came in between; this could be attributed to the higher number of heterogeneous users, periodic cleaning and dusting of the office furniture and computers.
Most common contaminating microbes for computer keyboards and mice were commensal skin organisms followed by some pathogenic microbes (Figures 2 and 3) however, key boards and mouse of internet café exhibited the highest percentage of pathogenic organisms (Figures 2 and 3). Computer keyboards are one of the most commonly- touched and shared surfaces today. By inference, anytime a keyboard is shared among two or more people, it becomes a risk for the spread of infection (Marsden, 2009). Thus, keyboards have become reservoirs for pathogens especially in hospitals and schools (Diggs etal., 2008). One should also note here that a reason for the increased percentage of contamination of computers is the difficulty of cleaning and disinfection (Marsden, 2009), as well as the misconception that cleaning keyboards could possibly damage therm. A possible solution to the spread of infectious diseases through keyboard sharing could be by making both cleaning and disinfection effective and easy (Marsden, 2009). The occurrence of bacteria on the handles of shopping carts was detected in four different locations that were geographically far apart. The percentage of contaminated cart handles was almost the same for all locations except for location 1, yet the observed difference was not significant (Table 1). People who push the shopping carts vary in their hygienic status; moreover the items that shoppers hold in their hands vary in the degree of cleanliness. The in-shop handling of different items is another factor that determines hand hygiene. Fluctuation between items such as fresh vegetables, fruits and then fresh dripping chicken, fish or frozen items would subject the hands to dampness and make them apt for picking up microbes. Those samples obtained from elevator buttons of shopping malls and of residential areas revealed nearly the same percent of contamination as those of other objects (Table 1). Formerly mentioned transient flora including potentially pathogenic bacteria such as S. aureus and Gram negative bacilli can be obtained from various sources in the environment some of which have been mentioned earlier such as shopping cart handles, elevator buttons, and supermarkets. Other sources could be contaminated surfaces, shaking hands with carriers of diseases or with patients (Ulger et al., 2009).
The hands of health care workers may become persistently colonized with such bacteria and consequentially spread it to others outside the healthcare premises through hand shaking or through touching various objects such as shopping carts, elevator buttons or computers.The potentially pathogenic S. aureus was isolated from the four tested objects but in lower percentages (Table 2).The ecologic niche for S. aureus in humans is in the anterior nares (Miller and Diep, 2008). One-quarter to one-third of healthy persons harbor S. aureus in the nose at any time (Kluytmans et al., 1997) which can easily be transferred to hands by simply rubbing the nose. In the present study one sixth of the isolates were S. aureus (15±0.02%). This strengthens the possibility of transfer of potentially pathogenic bacteria through human hands which could include antibiotic resistant bacteria such as community associated –MRSA (Miller and Diep, 2008). Inanimate objects have been known to play a role in the transmission of human pathogens either directly by surface to mouth contact or indirectly by contamination of fingers and subsequent hand to mouth contact (Rusin et al., 2002). Other routes of exposure include eyes, nose, and cuts on abraded skin. In the present study four inanimate objects have been shown to carry non pathogenic and potentially pathogenic bacteria. Even when contaminated surfaces containing relatively low numbers of organisms come into contact with the fingers and other surfaces, organisms may be transferred in sufficient numbers to represent a potential infection hazard (Scott and Bloomfield, 2008). On the other hand, the capability of pathogenic micro-organisms to exist in the viable but non-culturable (VBNC) state would pose risks of being overlooked during isolation. Furthermore, some investigators claim that non-culturable bacteria of selected species can be resuscitated to the culturable state as with Vibrio cholerae O1 that was isolated in the culturable form from stools of volunteers after ingestion of VBNC V. cholerae O1 (Colwell et al., 1996). Thus the use of conventional methods of isolation like those used in the present study would not necessarily reflect the actual bacterial contamination status on these objects and thus the actual microbial load may not have been elaborated. As reported by Lowbury and Fox (1953) and Rathmachers and Borneff (1977) soiling is an important factor in preserving viability of bacteria on hard surfaces. Thus dirty surfaces would harbor more bacteria than clean ones. This makes the process of dusting and removal of soil and dirt by simple cleaning procedures of paramount influence on the reduction of surface contamination. Although drying plays an important part in maintenance of hygiene on surfaces and other environ- ments, drying per se cannot be relied upon to prevent transfer of infection from laminate surfaces due to the resistance of some microbes to that measure (Scott and Bloomfield, 2008). Clinical investigations indicate that infection risks depend on numbers of organisms transferred and the immune status of the person (Scott and Bloomfield, 2008). Potentially pathogenic bacteria isolated from the four objects include Staphylococcus aureus, Pseudomonas spp. and other Gram -ve bacilli (Figure 1). These bacteria pose risk to the immunocompromised and immune suppressed persons. This study demonstrates that microbial contamination of computer keyboards, computer mice, shopping carts and elevator buttons is prevalent and that commensal skin organisms are the commonest contaminating microbes. The study also shows that Gram positive bacteria are transmitted most readily from environmental surfaces followed by Gram negative bacteria. The present investigation emphasizes the importance of good hand hygiene and adequate decontamination procedures applied to laminate surfaces, computer keyboards, mice and shopping carts. With the emergence of global infectious diseases like Swine flu and SARS a lot of supermarkets have been implementing measures of hygiene by providing disinfectants at entry and at several critical contamination points such as chicken and meat refrigerators. This could be taken as a step forward to minimize hand contami- nation. Such approaches should be undertaken in parallel with community education for hygienic standards, respiratory etiquette and hand washing. Methods of decontamination and disinfection of computers, cell phones and other sensitive electronics should be elaborated to consumers.
ACKNOWLEDGEMENTS The authors would like to thank the Faculty of Applied Medical Sciences at King Abdulaziz University in Jeddah, Saudi Arabia, for providing the space and facilities for carrying out this study. Thanks also to Mrs Abrar Algahtani, Mrs Ruqaih Algasham and Mrs Wed Bajned for their assistance during this study. REFERENCES Boyce JM, Pittet D (2002). 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. Infect. Control Hospital Epidemiol., 23: 3- 40 Cheesbrough M (2006). District laboratory practice in tropical countries. (Cambridge Univ Pr) Colwell RR, Brayton P, Herrington D, Tall B, Huq A, Levine MM (1996). Viable but non-culturable Vibrio cholerae O1 revert to a cultivable state in the human intestine. World J. Microbiol. Biotechnol., 12: 28- 31 Diggs R, Diallo A, Kan H, Glymph C, Furness BW, Chai SJ (2008). Norovirus outbreak in an elementary school—District of Columbia, February 2007. Centers for Disease Control and Prevention: Morb. Mortal. Wkly. Rep., 51: 1340-1343 Kluytmans J, Van Belkum A, Verbrugh H (1997). Nasal carriage of Staphylococcus aureus: epidemiology, underlying mechanisms, and associated risks. Clin. Microbiol. Rev., 10: 505-550 Lowbury EJL, Fox J (1953). The influence of atmospheric drying on the survival of wound flora. J. Hyg., 51: 203-214 Marsden R (2009). A Solid-Surfaced Infection Control Computer Keyboard., pp. 1-5 Miller LG, Diep BA (2008). Colonization, fomites, and virulence: rethinking the pathogenesis of community-associated methicillin- resistant Staphylococcus aureus infection. Clin. Infect. Dis., 46: 752- 760 Noskin GA, Stosor V, Cooper I, Peterson LR (1995). Recovery of vancomycin-resistant enterococci on fingertips and environmental surfaces. Infect. Control Hosp. Epidemiol., 16: 577-581 Rathmachers B, Borneff M (1977). Development of a new test method for surface disinfection procedures IV: Natural drying rates of microorganisms and their modification by environmental factors. Zentralblatt fur Bakteriologie, Parasitenkunde, Infektionskranheiten und Hygiene I Abteilung Originale, Reihe B., 165: 43-59 Reynolds KA, Watt PM, Boone SA, Gerba CP (2005). Occurrence of bacteria and biochemical markers on public surfaces. Int. J. Environ. Health Res., 15: 225-234 Rusin P, Maxwell S, Gerba C (2002). Comparative surface-to-hand and fingertip-to-mouth transfer efficiency of gram-positive bacteria, gram- negative bacteria, and phage. J. Appl. Microbiol., 93: 585-592 Scott E, Bloomfield SF (2008). The survival and transfer of microbial contamination via cloths, hands and utensils. J. Appl. Microbiol., 68: 271-278 Ulger F, Esen S, Dilek A, Yanik K, Gunaydin M, Leblebicioglu H (2009). Are we aware how contaminated our mobile phones with nosocomial pathogens? Annals Clin. Microbiol. Antimicrob. 8: 7.


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