There are billions of microorganisms, both harmful and benign, in the atmosphere. Human beings, animals as well as inanimate objects serve as habitats and breeding grounds for these microorganisms. One such inanimate object is the cell phone. "Tens of thousands of bacteria live on each square inch of a phone, including Staphylococcus". This bacteria is one of the most common causes of skin infections such as pimples and boils, but can also be implicated in more serious problems such as surgical wound infections, blood stream infections and pneumonia (James, 2009). Cell phone handsets are more contaminated than shoes, door knobs and toilets (Pugh, 2006). Cell phones also provide the ideal place for bacteria to grow because the heat they generate causes them to divide and multiply at a much faster rate than usual (James, 2009).
Cellular phones are commonplace in the world of today, and are convenient accessories taken for granted by most people. While most are to some extent aware of the hazards of long term use of mobile phones, such as the possibility of tumor development, cancer and radiation related illnesses, very few are even aware of the short term harmful effects, related to microbial contamination. Thus, such a study is warranted, if only to make the global population aware of the dangers involved in the use of one of the most common human possessions. Should one stop and think about the places a cellular phone goes, besides residing in pockets, purses or briefcases, one can begin to understand the depth of this issue.
Ø To identify the different types and level of microorganisms found on cell phones.
Ø To determine usage, safety perception and awareness of the harmful short term effects of cell phones caused by microorganisms.
Ø To provide literature and documented information which may assist future study.
Ø To compare the levels of microbial contamination on different areas of cell phones.
Ø To enhance existing knowledge by new findings on the research subject matter
2.1 Literature Review
A mobile phone or mobile (also called cellular phone and hand phone) is an electronic device used for mobile telecommunications (mobile telephone, text messaging or data transmission) over a cellular network of specialized base stations known as cell sites (Ulyseas, 2008).
It is called 'cellular' because the system uses many base stations to divide a service area into multiple 'cells'. Cellular calls are transferred from base station to base station as a user travels from cell to cell. The basic concept of cellular phones began in 1947, when researchers looked at crude mobile (car) phones and realized that by using small cells (range of service area) with frequency reuse they could increase the traffic capacity of mobile phones substantially. However at that time, the technology to do so was nonexistent (Bellis, 2007). Dr Martin Cooper, a former general manager for the systems division at Motorola, is considered the inventor of the first modern portable handset. Cooper made the first call on a portable cell phone in April 1973. He made the call to his rival, Joel Engel, Bell Labs head of research. Bell Laboratories introduced the idea of cellular communications in 1947 with the police car technology. However, Motorola was the first to incorporate the technology into portable device that was designed for outside of an automobile use (Bellis, 2007).
By 1977, AT&T and Bell Labs had constructed a prototype cellular system. A year later, public trials of the new system were started in Chicago with over 2000 trial customers. In 1979, in a separate venture, the first commercial cellular telephone system began operation in Tokyo. In 1981, Motorola and American Radio telephone started a second U.S. cellular radio-telephone system test in the Washington/Baltimore area. By 1982, the slow-moving FCC finally authorized commercial cellular service for the USA. A year later, the first American commercial analog cellular service or AMPS (Advanced Mobile Phone Service) was made available in Chicago by Ameritech (Bellis, 2007).
The advantage of a cell phone is that people are able to communicate over distances when they do not have access to a normal telephone or landline. The cell phone possesses the capability to facilitate voiced conversations as well as conversations carried out in the form of text messages, while the more sophisticated models grant access to the internet, allowing for research or other more luxurious pastimes such as online conversations, sport news, stock market information, and music downloads as well as many other endeavours.
To date, cell phone users include businessmen and woman, teachers, students, basically people from every walk of life. The near dependence of the human race on this convenience shows no sign of slowing or stopping. Thus the repercussions of poor cell phone sanitation can be very serious indeed.
A new study shows that cell phones used by hospital staff may spread bacteria, including the superbug, methicillin-resistant Staphylococcus aureus (MRSA), often called Staph. The spread of bacteria is particularly dangerous in the hospital setting. When patients already are sick, they are more vulnerable (Rogers, 2009). Phones get passed and passed around in circles. They are pressed up against the face of the next person, and then the next face, close to the next mouth, nose and ear. Before cell phones were ubiquitous, there really wasn't any object used on a regular basis that was passed quickly from hand to hand and pressed quickly up against one's face. The face, of course --- meaning the eyes, ears, nose and mouth --- is the precise entry point for most of the bacteria and viruses that make people sick with nasty colds, flu and illnesses such as mononucleosis (Rogers, 2009). The immediacy of the contact between cell phone users is important. Many times pathogens are not passed on only because they do not live very long outside the body. So, the habit of lending cell phones can lead to the spread of many potentially dangerous microorganisms.
A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory conditions. Microbial cultures are used to determine the type of organism, its abundance in the sample being tested, or both. It is one of the primary diagnostic methods of microbiology and used as a tool to determine the cause of infectious disease by letting the agent multiply in a predetermined media. Microbiological cultures utilize petri dishes of differing sizes that have a thin layer of agar based growth medium in them. Once the growth medium in the petri dish is inoculated with the desired bacteria, the plates are incubated in an oven usually set at 37 degrees Celsius (Absolute Astronomy, 2009).
2.3 Types of bacteria
Bacteria can be organized in many groups, such as proteobacteria, firmucutes, bacteriodetes, actinomycetes, mycobacteria, corynebacteria, spirochetes, chlamydiae and cyanobacteria.
Proteobacteria can be further subdivided into 5 clades: alpha, gamma-, beta-, delta-, and epsilon proteobacteria. Gamma Proteobacteria is the largest and most diverse subgroup of bacteria. Examples of bacteria which belong to this group are Escherichia coli, Acinetobacter baumannii and Salmonella enterica.
Escherichia coli (commonly abbreviated E. coli) is a Gram negative rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms (endotherms). Most E. coli strains are harmless, but some, such as serotype O157:H7, can cause serious food poisoning in humans, and are occasionally responsible for product recalls (Vogt et al 2005). The harmless strains are part of the normal flora of the gut, and can benefit their hosts by producing vitamin K2, or by preventing the establishment of pathogenic bacteria within the intestine (Hudault et al 2001). E. coli are not always confined to the intestine, and their ability to survive for brief periods outside the body makes them an ideal indicator organism to test environmental samples for fecal contamination. The bacteria can also be grown easily and its genetics are comparatively simple and easily-manipulated or duplicated through a process of metagenics, making it one of the best-studied prokaryotic model organisms, and an important species in biotechnology and microbiology (Feng et al 2002). Because E. coli lives in the human intestine, this has raised fears that genetically-engineered versions might escape from the laboratory and take up residence in humans, causing harm. For this reason, genetic engineering is done only on strains of E. coli that have been deliberately weakened so that they cannot survive for long in humans.” (Kimball 2003).
Staphylococcus is a genus of Gram-positive bacteria. Under the microscope they appear round (cocci), and form in grape-like clusters (Ryan et al 2004). The Staphylococcus genus includes just thirty-three species. Most are harmless and reside normally on the skin and mucous membranes of humans and other organisms. Found worldwide, they are a small component of soil microbial flora.
Staphylococcus aureus is the most common cause of staph infections. It is a spherical bacterium, frequently part of the skin flora found in the nose and on skin. About 20% of the population are long-term carriers of S. aureus (Kluytmans et al 1997). S. aureus can cause a range of illnesses from minor skin infections, such as pimples, impetigo (may also be caused by Streptococcus pyogenes), boils (furuncles), cellulitis folliculitis, carbuncles, scalded skin syndrome and abscesses, to life-threatening diseases such as pneumonia, meningitis, osteomyelitis, endocarditis, toxic shock syndrome (TSS), bacteremia and sepsis. Its incidence is from skin, soft tissue, respiratory, bone, joint, endovascular to wound infections. It is still one of the five most common causes of nosocomial infections, often causing postsurgical wound infections. Staphylococcus aureus is catalase positive and is able to convert hydrogen peroxide to water and oxygen, which makes the catalase test useful to distinguish staphylococci from enterococci and streptococci.” (Ryan et al 2004).
Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with about 1,500 species currently described (Kurtzman et al 2006). They dominate fungal diversity in the oceans (Bass et al 2007). Most reproduce asexually by budding, although a few do so by binary fission. A small knob or bud forms on the parent cell, grows and finally separates to become a new yeast dell. Although this is the most common method of reproduction, yeasts also multiply by the formation of spores.” (Pelczar and Reid 1965).
Yeasts are unicellular, although some species with yeast forms may become multicellular through the formation of a string of connected budding cells known as pseudohyphae, or false hyphae as seen in most molds. (Kurtzman et al 2005) Yeast size can vary greatly depending on the species, typically measuring 3-4 µm in diameter, although some yeasts can reach over 40 µm (Walker et al 2002).
Yeasts are chemoorganotrophs as they use organic compounds as a source of energy and do not require sunlight to grow. Carbon is obtained mostly from hexose sugars such as glucose and fructose, or disaccharides such as sucrose and maltose. Some species can metabolize pentose sugars like ribose, alcohols, and organic acids (Barnett 1975).
Some yeasts are found in association with soil and insects (McHugh et al 2005). Yeasts including Candida albicans, Rhodotorula rubra, Torulopsis and Trichosporon cutaneum have been found living in between people's toes as part of their skin flora (Oyeka and Ugwu 2002). Yeasts are also present in the gut flora of mammals and some insects (Martini 1992).
Certain yeasts are pathogenic. However, yeast infections are much less common than are bacterial infections (Weiser: 1962). “Candida albicans is a diploid fungus (a form of yeast), which is capable of sexual reproduction but not of meiosis, and a causal agent of opportunistic oral and genital infections in humans. C. albicans is commensal and is among the gut flora, the many organisms which live in the human mouth and gastrointestinal tract. Under normal circumstances, C. albicans lives in 80% of the human population with no harmful effects, although overgrowth results in candidiasis.” (Ryan, 2003) “It is normally present on the skin and in mucous membranes such as the vagina, mouth, or rectum. The fungus also can travel through the blood stream and affect the throat, intestines, and heart valves.” (Kuang-Wen, 2008).
Molds (or moulds; see spelling differences) include all species of microscopic fungi that grow in the form of multicellular filaments, called hyphae (Madigan et al 2005). In contrast, microscopic fungi that grow as single cells are called yeasts. A connected network of these tubular branching hyphae has multiple, genetically identical nuclei and is considered a single organism, referred to as a colony or in more technical terms a mycelium.
Although some molds cause disease or food spoilage, others are useful for their role in biodegradation or in the production of various foods, beverages, antibiotics and enzymes. Molds are ubiquitous in nature, and mold spores are a common component of household and workplace dust. However, when mold spores are present in large quantities, they can present a health hazard to humans, potentially causing allergic reactions and respiratory problems.
Some molds also produce mycotoxins that can pose serious health risks to humans and animals. Some studies have claimed that exposure to high levels of mycotoxins can lead to neurological problems and in some cases death. Prolonged exposure, e.g. daily workplace exposure, may be particularly harmful. Research on the health effects of mold has not been conclusive. The term toxic mold refers to molds that produce mycotoxins, such as Stachybotrys chartarum, and not to all molds in general.
There are thousands of known species of molds, which include opportunistic pathogens, saprotrophs, aquatic species, and thermophiles (Ryan et al 2004). Typically, molds secrete hydrolytic enzymes, mainly from the hyphal tips. These enzymes degrade complex biopolymers such as starch, cellulose and lignin into simpler substances which can be absorbed by the hyphae. In this way, molds play a major role in causing decomposition of organic material, enabling the recycling of nutrients throughout ecosystems. Many molds also secrete mycotoxins which, together with hydrolytic enzymes, inhibit the growth of competing microorganisms (Ryan et al 2004).
2.7 Microbial Analysis
The size of individual microorganisms does not allow for detailed study and the gathering of significant amounts of information from the examination of an individual. The work of the microbiologist involves the study of populations. Populations are obtained by growing microorganisms, under more or less well defined conditions. These are known as microbiological cultures. A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory conditions. Microbial cultures are used to determine the type of organism, its abundance in the sample being tested, or both. It is one of the primary diagnostic methods of microbiology and used as a tool to determine the cause of infectious disease by letting the agent multiply in a predetermined media. There are many different types of culture media used in microbiology. Many are specifically designed to identify one or more different species of microorganism.
Mannitol salt agar or MSA
This is used to identify Staphylococcus aureus. MSA is a commonly used growth medium in microbiology. It contains a high concentration (~7.5%-10%) of salt (NaCl), making it selective for Micrococcaceae and Staphylococcus since this level of sodium chloride is inhibitory to most other bacteria. “It is also a differential medium, containing mannitol and the indicator phenol red. Acid production as a result of mannitol fermentation, a feature of several clinically significant species such as Staphylococcus aureus, will result in the agar's normal red color changing to yellow. Mannitol fermentors produce a yellow colony while non-mannitol fermentors will produce a reddish/purple colony. It is used for the selective isolation of presumptive pathogen (pp) Staphylococcus.” (Austin Community College, 2007)
Eosin methylene blue agar or EMB
“This is a selective stain for Gram-negative bacteria. It is a blend of two stains, eosin and methylene blue in the ratio of 6:1. A common application of this stain is in the preparation of EMB agar, a differential microbiological medium which inhibits the growth of Gram-positive bacteria and provides a color indicator distinguishing between those organisms that ferment lactose versus those that do not.” (Atlas, 2004)
EMB is used to identify E.coli. If E.coli is grown, it will give a distinctive metallic green sheen (due to the metachromatic properties of the dyes). It is the only bacterium that reacts this way to EMB so it can be quickly used to identify E. coli species.
Potato dextrose agar or PDA
This is a common microbiological media made from potato infusion, and dextrose (corn sugar). Potato dextrose agar is the most widely used medium for growing fungi and bacteria which attack living plants or decay dead plant matter. Common organisms that can be cultured on PDA are yeasts such as Candida albicans and Saccharomyces cerevisiae and molds such as Aspergillus niger.
Plate Count Agar or PCA
“This is a microbiological growth medium commonly used to assess or to monitor total bacterial growth of a sample. PCA is not a selective medium. The composition of plate count agar may vary, but typically it contains 0.5% peptone, 0.25% yeast extract, 0.1% glucose, 1.5% agar and pH adjusted to neutral at 25 degrees Celsius.” (Atlas, 2004).
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* B.A. Rogers (2009) “Cell Phones, Staph and Superbugs and My Sick Child”
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* Bass D, Howe A, Brown N, Barton H, Demidova M, Michelle H, Li L, Sanders H, Watkinson SC, Willcock S, Richards TA. (2007). "Yeast forms dominate fungal diversity in the deep oceans"
* Kurtzman CP, Fell JW (2005). “Biodiversity and Ecophysiology of Yeasts”
* Suh SO, McHugh JV, Pollock DD, Blackwell M. (2005). "The beetle gut: a hyperdiverse source of novel yeasts"
* Oyeka CA, Ugwu LO. (2002). “Fungal flora of human toe webs. Mycoses”
* Martini, A (1992). "Biodiversity and conservation of yeasts"
* Indoor Environmental Quality (2008): “Dampness and Mold in Buildings.” National Institute for Occupational Safety and Health.