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The effect of different disinfectants on sterilizing the bacterial concentration of
Staphylococcus epidermidis on computer keyboards
Arlen ChenSpring Valley High School
120 Sparkleberry LaneColumbia, SC, 29229
1/19/06
Introductiono Recently, it has been discovered
that potentially harmful bacteria can survive on computer keyboards and keyboard covers.
o Some of the bacteria tested in the studies can cause complicated abdominal infections, pneumonia, and different skin infections.
o Therefore, the disinfection of these bacteria from computer keyboards must be considered.
Introductiono Staphylococcus
epidermidiso Gram-positive, immobile,
grape-like clusterso Facultative anaerobe
o Ecology / Pathologyo Small, white colonieso Inhabits skin of healthy
humanso Only infects
immunocompromised humans
o Resistant to antibiotics, antibodies, phagocytosis
http://www.bact.wisc.edu/Bact330/nfS.epidermidis.jpeg
Introductiono Staphylococcus epidermidis
o Inhabits skin
o Infectionso Skin lesionso Pneumoniao Meningitiso Urinary tract infections
Introductiono Independent Variables
o Cloroxo Lysolo Formula 409o Disinfectant Keywipes
o Dependent Variableo Staphylococcus epidermidis
colonies left after disinfection
Previous Researcho Even though previous research
was conducted on the survival of bacteria on keyboards, there has not been any research conducted on determining which disinfectant is best to sterilize the bacteria.
o Therefore, the purpose of this study was to determine the ability of four disinfectants to sterilize Staphylococcus epidermidis on computer keyboards.
Hypothesiso Using Clorox for 10 minutes will
be the most effective way of sterilizing the bacteria.o Based on the fact that Clorox
contains Clorox and the halogen chlorine.
Materials
Staphylococcus epidermidisNutrient AgarNutrient BrothBeakersPetri DishesKeyboard KeysLysol
CloroxFormula 409Disinfectant KeywipesIncubatorAutoclaveSterile Cotton SwabsSterile Disposable Inoculating LoopsHot Plate
Experimental Design Diagram
No Disinfectan
t
Lysol Clorox
Formula 409
Disinfectant
Keywipes
4 Trials 4 Trials
4 Trials
5 Trials 5 Trials
DV: Growth of bacteriaC: Time incubated
Time disinfectant is appliedTime bacterium is appliedBacterium used on keyboards
Methodso Creation of nutrient agar and
broth.
o Staphylococcus epidermidis was transferred into the nutrient broth
o Broth was spread onto each key.
Methodso Each disinfectant was sprayed or
wiped on the five keys
o Sterile cotton swabs used to swab the surface of the key and streaked onto the corresponding agar plate.
o Once the streaking was completed, the agar plates were placed into the incubator at 31ºC for 24 hours.
Results
0
10
20
30
40
50
60
Control Lysol Clorox 409 Keywipes
Results
0
5
10
15
20
25
30
Control
Lysol
Clorox
409
Keywipes
Resultsx Control Lysol Clorox Formula 409 Disinfectant Keywipes
Trial 1 0 0 2 3 14
Trial 2 43 1 0 5 1
Trial 3 0 2 0 22(1) 44
Trial 4 19 3 1 22 58
Trial 5 53 9
Mean: 15.50 1.50 0.75 21 25.2StdDev: 20.40 1.29 0.96 20.04 24.51
ResultsANOVA Summary Table
x d.f. Sum of Squares Mean Square F p
Disinfectants 4 2207 552 1.78 .179
Error 18 5266 310 --- ---
Total 22 7472 -------- --- ---
Using the F-distribution table at a significance level of .05, the critical value (C.V.) is found to be 2.93.
Discussiono When examining the number of
colonies for each disinfectant, it was found that there was no significant difference between the mean number of colonies at α=0.05.
o Therefore, the experimental hypothesis was rejected; the disinfectants did not vary in their abilities to disinfect Staphylococcus epidermidis on computer keyboards.
Sources of Erroro Counting errors
o Outliers in the data
o Errors in data analysis.
o Small sample size
Future Researcho Different bacteria
o Have a larger sample size
o Other surfaces
o Other disinfectants
Acknowledgementso I would like to thank Mr. Soblo for
providing guidance, motivation, ideas, and advice throughout my research project, as well as allowing me to use his class as my lab.
o I would like to thank Ms. McAlpine for assisting me in ordering materials.
o I would like to thank Ms. Sutton for providing me with information and advice.
o I would also like to thank my family for their support and guidance throughout my project.
Literature Citedo Adams, D. (2005). Keyboards latest culprit in hospital Adams, D. (2005). Keyboards latest culprit in hospital
infections. infections. AMNewsAMNews. Retrieved May 2, 2005 from . Retrieved May 2, 2005 from http://www.ama-assn.org/amednews/2005/05/02/prl2050http://www.ama-assn.org/amednews/2005/05/02/prl20502.htm2.htm
o Bates, B. (2005). Computer keyboards act as bacteria Bates, B. (2005). Computer keyboards act as bacteria reservoir. reservoir. Family Practice NewsFamily Practice News 3535, 27. Retrieved August , 27. Retrieved August 6, 2005, from Health and Wellness Resource Center.6, 2005, from Health and Wellness Resource Center.
o Hannford, A. (2003 May 19). Key strokes; Mmmmmm; Hannford, A. (2003 May 19). Key strokes; Mmmmmm; bacteria: eating at your desk and swapping work bacteria: eating at your desk and swapping work stations can seriously damage your health, discovers an stations can seriously damage your health, discovers an anxious Alex Hannaford. anxious Alex Hannaford. The Evening Standard (London, The Evening Standard (London, England)England). Retrieved May 2, 2005, from Custom . Retrieved May 2, 2005, from Custom Newspapers (Infotrac-Gale).Newspapers (Infotrac-Gale).
o Leichman, A. (2005 January 11). Average office is Leichman, A. (2005 January 11). Average office is breeding ground for germs. breeding ground for germs. Knight Ridder/Tribune Knight Ridder/Tribune Business News Business News Retrieved May 2, 2005, from Custom Retrieved May 2, 2005, from Custom Newspapers (Infotrac-Gale).Newspapers (Infotrac-Gale).
o Marquis, R. (2005). In Marquis, R. (2005). In Microsoft EncartaMicrosoft Encarta. Retrieved . Retrieved August 6, 2005, from August 6, 2005, from http://encarta.msn.com/encyclopedia_761574409/Bacterihttp://encarta.msn.com/encyclopedia_761574409/Bacteria.htmla.html
o WebMDHealth. (2005). WebMDHealth. (2005). What’s lurking on your What’s lurking on your computer? Bacteria can quietly thrive on computer computer? Bacteria can quietly thrive on computer keyboards. keyboards. Retrieved May 1, 2005, from Retrieved May 1, 2005, from http://my.webmd.com/content/Article/104/107365.htm?http://my.webmd.com/content/Article/104/107365.htm?pagenumber=1pagenumber=1
The effect of different disinfectants on sterilizing the bacterial concentration of
Staphylococcus epidermidis on computer keyboards
Arlen ChenSpring Valley High School
120 Sparkleberry LaneColumbia, SC, 29229
1/19/06
