Toothbrush
The toothbrush is a tool used by everybody on a daily basis to clean the oral cavity, so it is one of the most important pieces of equipment known for proper dental hygiene. But sadly, toothbrushes are most commonly found in a bathroom near the sink, which is a good place to harvest hundreds of microorganisms. So no matter how sanitary the bathroom is, the fact that the toothbrush is consistently exposed to the mouth will inevitably result in bacterial growth on the toothbrush. A new toothbrush is usually not a favorable habitat for bacteria and fungi, but in some cases, toothbrushes are already slightly infected because there is not a regulation that states toothbrushes must be sold in a sterile package.1 Typically, the presence of microbes on the toothbrush is due to brushing because the mouth is a hospitable niche to many kinds of microbes. Therefore, the bacteria will transfer from the inside of the mouth to the toothbrush.2 In this way, the toothbrush is considered a niche for many microbes.
Toothbrush as a Niche
A toothbrush does not naturally contain nutrients to support bacterial growth. However, after brushing, food particles often cling to the bristles of the toothbrush. From being rinsed with water and coming into contact with the moist environment of the mouth, the toothbrush becomes moist. All together, these aspects make the toothbrush a more favorable environment for microbial growth. The pH of the toothbrush is irrelevant because the microbes are able to survive in a wide range of pH levels.3
Survival Rates of Bacteria
Bacteria in mouths can transfer to toothbrushes, so active brushing will cause bacteria to always be present on the toothbrush. After the toothbrush is used, the transferred bacteria can survive up to 6 hours at room temperature.4 While on the toothbrush, bacteria have the ability to colonize and multiply in numbers; however, the longer the toothbrush is left to dry, less moisture and nutrients will be available so the concentration of bacteria will begin to decrease.5 The majority of reduction in the concentration of microorganisms happens within 0 to 4 hours after brushing. After more than 4 hours, the decrease in the concentration of microorganisms occurs at a slower rate. When toothpaste is used, brushes show substantially lower numbers of colony-forming units compared to those without the use of toothpaste.6
Influence by Adjacent Communities
Microbes that inhabit a toothbrush must come from somewhere, and a good amount of bacteria on the toothbrush originate from just the mouth, a niche that inhabits a plethora of microbes. The contact of the toothbrush with an oral cavity will thus cause microbes to transfer to the toothbrush.
In addition, a toothbrush's niche can be affected by another toothbrush in close proximity by cross contamination in a communal environment, since a typical household uses a holder to store multiple toothbrushes. Bacteria living on one toothbrush can thus be transferred to another nearby toothbrush through contact.7 Occurrences like these will spread disease and infect others when using the newly infected toothbrushes. The same idea of bacteria transfer applies when sharing a toothbrush,8 which is a bad hygiene practice.
The toilet also harbors a community of bacteria that can be partially transferred onto the toothbrush. The bacteria is ejected from the toilet bowl after flushing. Results show that during the first two hours after flushing, bacteria are mostly found in a limited area near the toilet. After longer intervals, bacterial colonies are found to be more randomly distributed; the detection of coliform bacteria on surfaces after flushing are also observed 9
Therefore, it makes sense that individuals should store their toothbrushes in separate holders or locations. The exception is storing a toothbrush in a closed container or cabinet. According to the American Dental Association, dark and moist environments are more favorable towards the growth of microorganisms than open air.10
Conditions That Affect Bacterial Growth
The environments of toothbrushes are usually under normal conditions. The pH of the toothbrush may become more basic because most toothpastes have basic chemical compositions.11 The active ingredient is the reactive fluoride ions which are acidic but their concentrations are negligible compared to other chemical agents in the toothpaste1. The pH of a toothbrush is strictly determined by the chemical residues left behind after brushing which is the toothpaste itself with other minor factors. If the toothbrush is thoroughly washed with tap water, then the pH generally varies from 6-8 which is the pH of tap water. Once the toothbrush has dried, the microbe is no long affected by the environmental pH.
Who lives there?
There is a surprising number of microbes that live on a toothbrush which evaluated by Fernandes, V. H. and Cesar, D. L. A commonly identified pathogenic fungus is Candida and some pathogenic bacteria include Streptococcus, Staphylococcus and Lactobacillus which are all gram positive. These microorganisms could potentially cause diseases like gingivitis, pharyngitis, candidiasis, laryngitis, and dental decay if oral hygiene is not well maintained.
Which microbes are present?
You may refer to organisms by genus or by genus and species, depending upon how detailed the your information might be. If there is already a microbewiki page describing that organism, make a link to it.
Are there any other non-microbes present?
Plants? Animals? Fungi? etc. Candida albicans is a type of yeast that can be found on a toothbrush. It prefers to live in environments with low pH levels and a lot of moisture. Candida albicans are opportunistic human fungal pathogens that can cause disease in individuals who are immuno-compromised such as HIV/AIDS patients, individuals undergoing chemotherapy or individuals who have had a recent organ transplant (I, II).
Do the microbes that are present interact with each other?
Describe any negative (competition) or positive (symbiosis) behavior
Candida albicans are one type of many organisms that prefer the human mouth as their primary habitat but have abilities that allow them to survive on the barren surface of a toothbrush if they find themselves stranded there. C. albicans can do this by morphing from a free floating or planktonic form to one that is sessile and grows as a community in a biofilm. Biofilms may allow for overpopulation and nutrient load regulation. The formation of a biofilm requires C. albicans to grow hyphae which are multinucleated cell filments that absorb nutrients. They decide to build communities and grow hyphae based on different environmental and cell signals such as an increase in temperature, increase in pH levels, nutrient starvation and increased cell density (Martins)
Not only does Candida form biofilms among each other, but they also incorporate a variety of microbes into the biofilm that can benefit one other. A study was done on the effect of Streptococcus mutans and Candida glabrata on Candida albicans biofilms to better understand the interactions between multiple species of microbes and their environment. This is important because yeasts can easily re-colonize the oral cavity of an individual who has just undergone antimycotic treatment for oral candidosis, a fungal infection of the mucus membranes in the mouth commonly known as thrush(IV).
In their study, they observed that when Streptococcus mutans were present, the growth of both Candida albicans and Candida glabrata increased. These results suggest that the microorganisms may co-aggregate in order to enhance the adhesion process in biofilm formation. Not only did S. mutans increase the growth of both Candida species, but they also found a stimulatory effect between C. glabrata and C. albicans when they were co-cultured. By better understanding how these microbes survive in remote sites, such as a toothbrush, oral cavity re-colonization can be avoided by developing better sterilization techniques (IV).
Do the microbes change their environment?
Do they alter pH, attach to surfaces, secrete anything, etc. etc.
One way that C. albicans obtain what nutrients are on a toothbrush is through a regulatory cascade that controls the secretion of aspartic protease (Saps). C. albicans secrete Saps into their environment to degrade proteins and use them as a nitrogen source when there are no other nitrogen sources available such as ammonium or amino acids (III). This may also benefit other microbes in the biofilm by producing nitrogen in the environment that is available to be taken up.
Do the microbes carry out any metabolism that affects their environment?
Do they ferment sugars to produce acid, break down large molecules, fix nitrogen, etc. etc.
C. albicans and C. glabrata grow in higher numbers in the presence of glucose when compared with sucrose but can survive and grow when either one is available on a toothbrush (IV).
Current Research
Enter summaries of the most recent research. You may find it more appropriate to include this as a subsection under several of your other sections rather than separately here at the end. You should include at least FOUR topics of research and summarize each in terms of the question being asked, the results so far, and the topics for future study. (more will be expected from larger groups than from smaller groups)
References
Edited by [James Lin, Natalie Nguyen, Nicholas Phung, Sarah Fernandes], students of Rachel Larsen
