Computer Keyboard

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Description of Niche

Microbes found in air below altitude of 500 feet in clear weather include spores of Bacillus and Clostridium, ascos­pores of yeasts, fragments of myceilium and spores of molds and strepto­mycetaceae, pollen, protozoan cysts, algae, Micrococcus, Corynebacterium etc. In the dust and air of schools and hospital wards or the rooms of persons suffering from infectious diseases, microbes such as tubercle bacilli, streptococci, pneumococci and staphylococci have been demonstrated. These respiratory bacteria are dispersed in air in the droplets of saliva and mucus produced by coughing, sneezing, talking and laughing. All of these microbes from air are possibly found on computer keyboard in different locations. Microbes that appear on the keyboard are always the result of human contamination. In practice, almost any microbe can appear on a keyboard, but survival depends on environmental conditions of where the keyboard is placed and possible nutrients for the bacteria that are transferred to the keyboard as well. Spills and substance contamination further enhance survivability and presence of microbes.

Where is it located?


The niche usually exists wherever a computer is present. Generally, computers are found in offices, homes, hospitals, and schools. Anywhere there is an outlet, there is a possibility of a keyboard and computer present. The only time a keyboard would be without a computer is when it is in storage.

Physical Conditions?

What are the conditions in your niche? Temperature, pressure, pH, moisture, etc. The temperature of an idle keyboard is dependent on the temperature of the environment. The temperature of a keyboard in the deserts of Iraq will be much greater than in the cabins of Alaska. The temperature increases slightly with use since heat is produced from the hands. In a laptop keyboard, however, the temperature is usually higher and could fluctuate more since the keyboard is attached on top of the computer. The temperature of the inner components of the laptop directly influences that of the keyboard. When the computer is under a heavy load, the inner components of the laptop could rise up to temperatures of nearly 90 C and still function normally, which would considerably raise the temperature of the keyboard.

The pH of the keyboard is affected by the materials that it has come into contact with. Generally, the pH will most be affected by the sweat from the fingers. The pH of sweat could range from an acidic 5.0 to a slightly alkaline 7.2, depending on the rate of sweat of the individual, with a lower rate of sweating equating to a lower pH. [11] Since using the computer is usually a low stress activity, the rate of sweat will usually be slow and create an acidic sweat.

There is also oil from our finger tips.

The moisture of the keyboard niche will vary depending on the environment in which it is situated. Often times, it will seem dry. However, things like our breathe provide a little bit of moisture into the atmosphere, and the moisture has to settle somewhere. The moisture of the air is a key factor to the level of moisture of the keyboard.

The keyboard is usually mostly made of plastic, with some metal springs under the keys. There are some flexible keyboards that are made of silicone or polyurethane.

Since the crevices of the keyboard are hard to clean, constant keyboard use will provide a fairly constant food source for any bacteria living there. Dead skin cells are constantly being sloughed off, so a good amount falls into the crevices of the keyboard. The letters of the keyboard that are rarely used, such as the tilde and “F” keys, will be good spots for bacteria to thrive since they will not have to endure the clicking and pounding that the other keys experience. The space under the keys is usually dark and will be a safe location for bacteria to grow.

Influence by Adjacent Communities

There are many communities that come into contact with the keyboard. In general, the bacteria that lives on our skin, fingernails, hands, and anywhere the hands have been are likely to transfer new bacteria over to the keyboard. In a place where there is a lot of people moving in and out, such as a hospital or office, there is likely to be a good number of people that are sick, and through them comes the new bacteria that will eventually settle on the keyboard through the air or from physical contact.

Conditions under which the environment changes

The keyboard is a very dynamic environment. Food and drinks are commonly consumed in front and on top of the keyboard. This provides a constant source of food for anything that may be living there. Since the keyboard is constantly in contact with human hands, there will constantly be a stream of things leaving the hands and entering the keyboard or of course, leaving the keyboard and entering the hands. In the former case, bacteria from different niches could be transferred over if the hands have not been sanitized. In the later case, already preexisting bacteria will start to grow will transfer onto the hands and then onto the new surfaces that the hand will come into contact with.

Current Research

Antimicrobial keyboards have begun to emerge from the market. The majority of these keyboards utilize nano silver as a lining to help prevent bacterial growth. [12]. The reason for using silver is that it has a broad effect against microbes, which is useful for killing a large number of bacteria. This technology has been implemented in medical devices in recent years in order to combat the formation of biofilms. The theory is to make the surface inhospitable for bacterial growth and the formation of biofilm. Nano silver is usually in solution and will be embedded onto the surface of the device. When it comes into contact with moisture, such as from one’s hands or some sort of body fluid, it will slowly be oxidized and release the ionic form of silver. These silver ions have shown antimicrobial activity, which helps in preventing the formation of biofilm, yet the amount is so small that it is safe for human use. The claim of its safety, however, is still under research. Popular keyboard manufacturing companies like Companies like Microsoft and Logitech have already implemented antimicrobial technologies in some of their products.

Destroy Germs Upon Contact

Nowadays, people are becoming more health-conscious. There is a high appeal in developing products that are able to remove disease-causing bacteria. These products can cover objects people regularly use such as computer keyboards, doorknobs, and telephones. They can reduce the chances of spreading diseases from one person to another. [9]

Currently, there is a research on creating surfaces that can kill bacteria upon contact. Poly(4-vinyl-N-alkylpyridinium bromide) was fixed on a glass slide as a surface that can kill bacteria. A slide was squirted with distilled water containing bacteria. This created a model of people coughing or sneezing against the surface. The slide was then air dried, and then later on the number of bacterial colonies were counted. The surface “acylated with acryloyl chloride, copolymerized with 4-vinylpyridine, and N-alkylated with different alkyl bromides” eliminated 94 ± 4% of Staphylococcus aureus. A slide with poly(4-vinylpyridine) and alkylated with hexyl bromide destroyed 94 ± 3% of S. aureus. And finally, Staphylococcus epidermidis (a Gram-positive bacteria), Pseudomonas aeruginosa (a Gram-negative), and Escherichia coli decreased by a hundredfold on a slide with N-hexylated poly(4-vinylpyridine). [9]

Bacterial Conditions of a Keyboard in a Healthcare Environment

In a discussion of the bacterial niche of a keyboard, so much depends on the user and what bacteria, and contaminants a user brings to the device. This section will focus on niche conditions that present itself as optimal for bacteria in an environment exposed to active practice of medicine.

Significant amount of bacteria on keyboards in healthcare environments is transferred through wet gloves, contaminated gloves, or poor hygiene from healthcare specialists. Bacterial transmission results from tapping on the keys and regular usage of the device, which may incur contaminants such as blood, secretions, or other various sticky substances in such a healthcare environment. [1]. From tests carried out, 95% of cultures from keyboards tested positive for microorganism though most were simple skin flora. [3]. The focus of research has been on pathogenic bacteria that pose threats to nosocomial infections.


Bacteria found on Keyboard in a Healthcare Environment

Bacteria that are often found in a healthcare environment include coagulase-negative Staphylococcus, Bacillus species, Corynebacterium species, streptococci, Clostridium Perfringens, Enterococcus species, Staphylococcus aureus, gram negative bacteria, and fungi. [2]. Of siginifcant importance in healthcare environments involve antibiotic resistant strains of microbes which include Staphylococcus aureas, Vancomycin-resistant enterococci, and methicillin-resistant Staphylococcus aureas (MRSA). The capability of these bacteria to survive for more than 24 hours further increases their chances of contamination in other places.

The environmental conditions vary depending on temperatures around the keyboard and whether or not the keyboard is on a laptop. If the keyboard is on a laptop it could possibly provide heat and moisture for long enough durations to have an affect on bacteria such as Enterococcus, which is known to survive a wide range of environmental conditions. Studies have shown, however, that the presence of serum or albumin (known contaminants on keyboards touched by wet gloves), and a low temperature, with high humidty results in longer lifetime of bacteria on contaminated surface. Many nosocomial pathogens can also survive on dry inanimate surfaces for months. [4].

Coagulase-Negative Staphylococcus / Staphylococcus aureus - Usually found on skin or in the nasal environment and only survives on dry skin on the outside of the body. Appears on keyboards quite a bit as a result of usage. Methyacin resistant strain of Staphylococcus aureus found on keyboards a high percentage of the time in hospital environments which can cause infections in patients. [1].

Clostridium perfringens - Usually found in human gastrointestinal tracts and environments such as sewage and soil, however, in a healthcare environment can cause gas gangrene. Probably will not survive long on a keyboard as its primary target is living tissue. Found on keyboards at lesser degrees

Enterococcus - Enterococcus bacteria is usually find in the bowel and are known to be able to survive adverse conditions that other bacterial usually wont grow in. They are known to survive at temperatures of 60C and in anaerobic conditions with varying degrees of acidity. Enterococcus species represents some of the highest rates of appearances in hospital environment keyboards. [5].

Corynebacterium - Commonly found on human skin and mucous membranes

Streptococcusm - Mostly anaerobic while some are facultative anaerobes, they do not carry out oxidative phosphorylation and can survive in more acidic environments which might be present on keyboards. Medically siginificant streptococcus require lots of amino acids, vitamins, and nutrients thus are not normally found isolated in an environment. [10].

Current Research in the Healthcare Environment

Current research involving keyboard hygiene in the healthcare environment involve optimal cleaning practices and cleaning agents. Cleaning practices and agents are being tested to determine optimal results of cleanliness. Further non-bacterial research involves financial costs of nosocomial infections.


Top spills on keyboard:

Coffee, Beer, Soda

For us: I spilled a drink on my keyboard! Oh no!!!!

A computer's keyboard will usually survive a liquid spill (if not too much). Turn the keyboard upside down on top of a kitchen towel and leave it alone for a while. After wiping the top of the keys down with a slightly damp cloth, the keyboard will look all new again. But some of the liquid may ooze down the gaps…

For bacteria: Oh yeah, new niche for me!!!

Physical condition

In general, the liquid drinks that people enjoy are usually acidic. Examples are coffee, beer, and soda, which usually have a pH about 4.0 to 5.0. Thus, if these drinks are spilled on the computer keyboard, the pH for this specific niche will be decreased temporarily. Since all drinks contain liquid, these spills will provide a huge amount of moisture to the niche. (All the assumptions are made under room temperature and pressure.)

Do these conditions change or are they constant?

The conditions for the niches on computer keyboard are constantly changing. For laptops, the temperature of the keyboard varies depend on the activity of the computer. Also, the amount of spills and how fast the spills dry out will affect the level of moisture in the niches. In some cases, certain conditions will change depend on the location of the computer or the weather. The pressure will mostly be constant for this niche.


The main microbes responsible for the contamination from spills are bacteria, molds and yeasts from the air.

For coffee and soda:

The main nutritional contents in coffee drinks are mostly carbohydrates, water, and proteins (if milk is added). The nutrient that is used quickest by bacteria is lactose. Some bacteria such as lactococci and lactobacilli will convert lactose to glucose and galactose, then into lactic acid. Some bacteria will attack the protein and decompose it for their own use. If air is present, molds can use lactic acid, decompose some protein and fat. The main nutritional content in soda drinks is also carbohydrate and water. The spills of soda on the keyboard provide a carbohydrate-rich environment for bacteria to grow.

For beer:

Beer is made by a process “brewing” from grains (wheat or millet in some countries), hops, sugar, yeast and water. The unique bitter taste of beer comes from the resins and oils in the hop flowers. Different types of beer are produced by using different strains of the yeast saccharomyces cerevisiae through fermentation. Thus when beer is spilled on keyboard, some saccharomyces cerevisiae can be found in the niche. After a day or two, when the spilled beer becomes spoiled, another microbe lactic acid bacteria and/or acetic acid bacteria can be detected. These are the bacteria which cause the off-flavors and cloudiness in the beer. They are usually found in other decomposing plants and lactic products produce lactic acid as the major metabolic end-product of carbohydrate fermentation. These gram-positive bacteria are rod-shaped bacilli or coccus characterized by an increased tolerance to a lower pH range, thus acidic condition of the niche favors their survival. Carbohydrate source is needed because most species are incapable of respiration.

After days.....

Bacteria need lots of water to grow well, so having the drinks dry in the keyboard will gradually discourage their growth. When the residue is completely dried and when carbohydrate and proteins are used up, things will stop happening until the spot gets wet again, with moisture or more spills.

Interactions between bacteria

Certain bacteria can influence the growth of other bacteria; for example, lactic acid bacteria will make conditions unfavorable for Salmonella bacteria. Other strains produce nisin, which inhibits growth of Listeria and botulism organisms. An estimated 99% of bacteria live in ‘biofilms’ rather than in single-species colonies. These are complex colonies made up of a number of different species of bacteria structured on a layer of slime produced by the bacteria. Fungi, algae, and protozoa may also inhabit the biofilms.

An interesting fact about coffee

Brazilian researchers found that coffee extracts inhibited bacteria growth regardless of brand, roast or acidity. [13] Specific compounds within the coffee were identified as the source of the effect. Coffee compounds found to inhibit bacterial growth included caffeic acid, caffeine, chlorogenic acid, protocatechuic acid and trigonelline. Caffeine was particularly effective against Salmonella, accounting for 50% of coffee’s antimicrobial effect. In addition to caffeine, trigonelline and protocatechuic acids were found to be potential natural antimicrobial agents against Salmonella.

Keyboards in Schools

Students from the University of Washington discovered an excessive amount of fecal coliform bacteria on its campus’s computer keyboards. They were doing this as a part of a research project. The fecal coliform bacteria came from keyboards that are found on the most active parts of campus, one of them the undergraduate library. [7]

Fecal coliform bacteria are part of the Enterobacteriacae family. Citrobacter, Enterobacter, Escherichia coli, and Klebsiella also belong in this family. Fecal coliform bacteria originate in warm-blooded animals’ digestive tracts. They are rod-shaped, gram-negative bacteria. They are usually linked with Vibrio cholera, which is a type of Hepatitis virus and also comes from digestive tracts. Fecal coliform bacteria are removed from the tract with fecal matter. [8]

The swabbing technique was used to collect small samples from 30 computer keyboards. Because of what the students found, it is suggested that other forms of disease-causing bacteria can be found on keyboards. [7]

Current Research

Current research suggests that students in a city college use computer keyboards that are laden with antibiotic-resistant staphylococci. Methicillin (oxacillin)-resistant staphylococci were discovered in 17 out of 24 keyboards using genetic and biochemical analyses. Two computer keyboards had methicillin (oxacillin)-resistant Staphylococcus aureus (MRSA). Another two had methicillin (oxacillin)-resistant Staphylococcus hominis (MRSH). And finally five keyboards had methicillin (oxacillin)-resistant Staphylococcus epidermidis (MRSE). All three (MRSA, MRSH, and MRSE) was found in one keyboard. [6]

Scientists sampled the exterior of 24 keyboards for bacteria using swabs. The sampling was carried out during the usual student traffic in computer stations. The swabs that contained the bacteria were incubated in a broth containing oxacillin. After 48 hours, growth was seen on 17 of the samples. They were black, round, and shiny which is what Staphylococcus looks like. After further testing using PCR analysis, it was determined that two of the five keyboards that contained S. aureus were methicillin-resistant. This finding proposes that the MRSA came from humans. In addition, the investigation showed that five out of the ten computer keyboards that were tainted with S. epidermidis were methicillin-resistant. Few of the keyboards had a nosocomial pathogen, which was a methicillin-resistant S. hominis. [6]

The discovery of antibiotic-resistant staphylococci on computer keyboards draws much needed attention to good sanitary habits after utilizing public facilities. Additionally, touching of the mouth or the nose while operating the keyboard could have contributed to the contamination because humans can transport staphylococci from the nasal passages. However, the degree of diffusion of the bacteria to humans and its survival rate on the keyboard is yet to be determined. [6]

Antibacterial Keyboard Hygiene


It is recommended that one washes their hands before and after using a keyboard. This will help limit the spread of germs between the keyboard and all other environments that one’s hands will come into contact with. Using a commercial keyboard cleaner is also recommended to occasionally disinfect the keyboard. There are many ways to clean a keyboard with disinfectants. Of the methods researched to combat Enterococcus species, sterile water was useless, while alcohol only did slightly better than water, eliminating a measly 3% of the bacteria. Clorox wipes appear to work the best eliminating 100% of the bacteria with use. For antibiotic resistant bacteria, disinfectants containing quartenary ammonium compounds work best for health care environments.. [2]. To clean the crevices of the keyboard without disassembling it, it is best to flip it upside down and then use a can of compressed air to dislodge food and dust particles that may be residing under the keys. Food should generally not be consumed in front of or on top of a keyboard because it this will provide ample food source for bacteria. Liquids are generally safer to consume around the keyboard, but they do still pose a risk since accidents can happen. In the case that a spill does occur, the consequences could be dire as this will create a haven for bacteria.


1. Fukata T et al., Anaesthetists' role in computer keyboard contamination in an operating room, J Hosp Infect (2008), doi:10.1016/j.jhin.2008.05.23

2. Rutala, William et al., Bacterial Contamination of Keyboards: Efficacy and Functional Impact of Disinfectants, Infection Control and Epidemiology April 2006, Vol. 27, No. 4

3. Schultz, Maureen et al., Bacterial Contamination of Computer Keyboards in a Teaching Hospital, Infection Control and Hospital Epidemiology April 2003 Vol.

4. Kramer et al; licensee BioMed Central Ltd., How long do nosocomial pathogens persist on inanimate surfaces? A systematic review. BMC Infectious Diseases 2006, 6:130.,

5. Hartman B et al., Computer Keyboard and Mouse as a Reservoir of Pathogens in an Intensive Care Unit., J Clin Monit 2004; 18: 7-12

6. Kassem, Issmat et al., Public computer surfaces are reservoirs for methicillin-resistant staphylococci, The ISME Journal (2007) 1, 265–268; doi:10.1038/ismej.2007.36; published online 31 May 2007.



9. Tiller, Joerg C. et al., Designing surfaces that kill bacteria on contact, PNAS May 22, 2001 vol. 98 no. 11 5981-5985

10. Nizet, Victor., Nizet Lab: Streptococci.

11. Advances in Fingerprint Technology By Henry C. Lee, Robert E. Gaensslen

12. The Role of Antimicrobial Silver Nanotechnology, Bruce Gibbins and Lenna Warner


Edited by Chia-Wei Chou, Eunice Aquino, Vincent Lam, & Ye Han, students of Rachel Larsen