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Bacterial contamination of computer keyboards and mice, elevator buttons and shopping carts

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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.
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African Journal of Microbiology Research Vol. 5(23), pp. 3998-4003, 23 October, 2011
Available online http://www.academicjournals.org/ajmr
ISSN 1996-0808 ©2011 Academic Journals
Full Length Research Paper
Bacterial contamination of computer keyboards and
mice, elevator buttons and shopping carts
A. K. Al-Ghamdi1, S. M. A. Abdelmalek2* A. M. Ashshi3, H. Faidah3, H. Shukri4 and
A. A. Jiman-Fatani4
1College of Applied Medical Sciences, King Abdulaziz University Jeddah, Saudi Arabia.
2Faculty of Pharmacy and Biomedical Sciences, University of Petra, Amman Jordan.
3College of Applied Medical Sciences, Umm Al-Qura University, Mecca, Saudi Arabia.
4King Abdulaziz University Hospital, Saudi Arabia.
Accepted 26 September, 2011
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
*Corresponding author. E-mail: sabdelmalek@uop.edu.jo. Fax:
00962-6-5715570.
Abbreviations: CK, Computer keyboards; CM, computer mice;
Shc, shopping carts; EB, elevator buttons.
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
Al-Ghamdi et al. 3999
Table 1. Sites sampled for the presence of bacteria and perc entage contamination.
Site No. of samples Percentage contamination Total percentage contamination
Computer key boards
93
Homes 25 88
Offices 25 92
Internet café 50 100
Computer mice
95
Homes 25 91
Offices 25 91
Internet Café' 50 100
Shopping carts handles
93
Supermartket 1 25 89
Supermartket 2 25 95
Supermartket 3 25 95
Supermartket 4 25 92
Elevator buttons
97 Shopping Malls 50 96
Residential Buildings 50 98
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 f irmly 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
(Cheesbrough, 2006).
Statistical analysis
One-way ANOVA test was used to compare the means of all
bacteria found on computers (mouse and keyboard) at different
places (Internet Cafe, Office and Home). An alpha level of .05 was
used for all statistical tests.
RESULTS AND DISCUSSION
The 30 control samples showed no bacterial growth. The
average rate of bacterial contamination of the four objects
was 95.5% with the elevator buttons showing the highest
percentage (97%) and computer keyboards from homes
showing the least (88%) (Table 1). Qualitative analysis of
bacterial isolates revealed the abundance of normal flora
isolates belonging to Coagulase negative Staphylococci
(ConS) and Gram positive bacilli in all four objects.
Potential pathogens such as Staphylococcus aureus,
Pseudomonas spp. and Gram negative bacilli were also
isolated but in lower frequencies (Table 2). Distribution of
isolates between the four different objects was almost
identical (Figure 1). However percentage of different
isolates recorded from computer keyboards and mice of
internet cafes was significantly higher (p<0.000) than
those from houses and offices (Figures 2 and 3).
The bacterial occurrence on four commonly used public
surfaces was investigated in this study. Surfaces varied
4000 Afr. J. Microbiol. Res.
Table 2. Percentages of bacterial isolates on each object.
Isolated bacteria CK (%) CM (%) Shc (%) EB (%)
Coagulase-negative staphylococci 85 88 87 84
Gram-positive bacilli 58 60 55 60
Staphylococcus aureus 20 19 14 11
Pseudomonas spp. 11 10 10 10
Gram-negative bacilli 14 11 8 7
Percentage
Figure 1. Distribution of bacterial isolates in the four objects computer key boards (CK),
computer mice (CM), shopping cart handles (SCH) and elevator buttons (EB).
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
Al-Ghamdi et al. 4001
Figure 2. Comparison between isolates from computer keyboards from homes, offices and
Internet cafes.
Figure 3. Comparison between percentage isolates from computer mice from homes, offices
and internet cafes.
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 et
al., 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
4002 Afr. J. Microbiol. Res.
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 v ary 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.
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... The computer equipment may acts as a reservoir for the transmission of potential hazardous or pathogenic microorganisms. The ability of a computer to act as fomites has been previously documented in health care on hospital environment [5] .In fact 80 % of infections are spread throughout hand contact with hands or other objects the viability of Gram positive and some Gram negative organisms under various environmental conditions have been found to survive in dry conditions and on various fabrics utilized in the health care environment [2]. ...
... In our study Gram positive bacilli bacteria were more frequently (90.8) % (X 2 =4.9, P<0.05) and Gram negative bacilli (80.4) isolated from all surfaces computers (X 2 =6.2 , P<0.05) , this could be in part due to the fact that survival of Gram positive spores on laminate surfaces is great than that of Gram negative organisms (4,2,17). ...
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... Several studies have shown that cell phones contaminated with pathogenic bacteria play a big role in the spread of infectious disease (Brady et al., 2006;Tagoe et al., 2011). Many users do not generally know the microbial load on many regular objects within their living and workplaces (Al-Ghamdi et al., 2011;Shalinimol, 2016). The unclean ways of handling such objects make them a cardinal reservoir of an assembly of pathogenic microorganisms (Zakai et al., 2016;Adhikari et al., 2018) thus mobile cell phones surfaces might serve as fomites in the transmission of these microbes (Bhoonderowa et al., 2014). ...
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