Microbiomes are all around us, in your gut, on your hands, in your ear, and especially in your mouth. The oral microbiome is one of the most interesting subjects to study because of the complex environment in your mouth. It’s wet, warm, and depending on the person can have a high or low pH. Many factors come into play when it comes to the health of your oral microbiome. One of those factors is chlorhexidine (CHX), an antiseptic mouthwash that has been around since the 1970s. Dentists regularly use chlorhexidine, so how does this affect our microbiome?
Chlorhexidine is an antiseptic agent that is used because of its long-lasting antibacterial effects and the large spectrum of action. It’s used by dentists because there have been studies that have shown its effectiveness in the clinical management of plaque, gingival inflammation, and bleeding (Amoian et al., 2017). Other studies show that it helps reduce the proliferation of some bacterial species associated with periodontal disease as well as reducing levels of bacteria that colonize the top surface of the tongue (Bescos et al., 2020).
Mental health diseases like depression and anxiety have plagued humans presumably since we achieved sentience, and lately it seems like the mental health crisis in America is getting worse and worse. Everyone blames this rise on something different; social media, the pandemic, tumultuous politics, or just the dramatics of younger generations. No matter where the blame is placed, statistics show that the rise in the number of diagnoses is real. Almost all mental health diseases show growth, but anxiety and depression have skyrocketed (ADAA). Even before the COVID 19 pandemic, anxiety was at an all time high, as shown in the figure below.
Fig. 1: These graphs show the number of people diagnosed with anxiety in 1990 (left) and 2017 (right). The United States shows a drastic increase. Darker areas indicate higher numbers of anxiety diagnoses. Image sourced from Our World in Data. Continue reading “Mental to Dental Connection”
As children we are told to brush our teeth and floss twice a day. An uncomfortable dental experience as a child can create dental anxiety in adulthood. This anxiety can prevent patients from seeking the care they need. The development of caries, or cavities, in the mouth can have lasting impacts if not treated properly in both children and adults. Caries develop on teeth due to the creation of an acidic environment from the bacteria inhabiting the mouth (Marsh 1994). The acidity eats away at the enamel, and eventually the softer pulp, or dentin, within the tooth, leaving an exposed and sensitive area that requires medical attention (Bowen et al. 2017). The prevalence of decay in primary teeth is notably higher in children aged 1 to 4 while young adults aged 15-19 years old have a higher prevalence of decay present in permanent teeth (Kassebaum et al. 2017). Because children develop higher levels of cavities than adults, protecting young permanent teeth is an important area for research. Why are children more likely to develop caries? And what can be done to lessen the spread of this disease? For many years scientists attributed the development of caries to the bacterial species Streptococcus mutans. With the advent of new technology and further information of how microbes interact with each other, scientists are now looking at old problems with modern solutions. Instead of merely describing the presence of microbes, scientists are now beginning to see what is happening between various microbial species in the human microbiome. Continue reading “It Takes a Village: Selection Drives the Formation of Dental Caries in Children”
The geographical location of the Yanomami tribe as a whole. The specific village exists in the highlighted region. (Image courtesy of Viralfast)
Background
The Yanomami people are patches of isolated South American tribes who occupy mountainous regions of southern Venezuela. Recently, a Yanomami tribe of 34 subjects discovered by helicopter, was investigated by a team of researchers who accompanied medical care professionals who were providing care to the villagers. These researchers, Clemente et. al. (2015), then wrote the paper, “The microbiome of uncontacted Amerindians’ to analyze this population which was uniquely untouched by Western Society. An interesting topic that this research paper addresses is antibiotic-resistant bacteria. Antibiotic-resistance are the adaptations of a bacterial species in response to antibiotics. Antibiotics are medications that have been developed in more recent times to destroy bacteria cells but not human cells. They do this by targeting specific differences between the two types of cells, for instance, penicillin inhibits the synthesis of the peptidoglycan layer of bacterial cell walls a feature not present in animal cells. Other bacteria have distinct DNA replication processes and some antibiotics are able to interrupt that function as well. This Yanomami population is intriguing because their microbiomes are likely the most accurate representation of an ancient human microbiome due to their isolation from the Western world. The presence of antibiotic-resistant bacteria in the Yanomami gut provides evidence for the claim that antibiotic-resistant bacteria have been around since before the invention of antibiotics, so stay tuned for a persuasive evidentiary argument further down. Clemente et. al.also state that the Yanomami population that is sampled is the most diverse microbiome ever recorded. It is important to understand what kind of diversity the researchers are talking about. The Yanomami show extremely high beta diversity when compared to Guahibo, Malawi, and U.S. populations but exhibit low alpha diversity amongst individuals in the village population. Beta diversity represents the differences in species composition among samples while alpha diversity is just the diversity of each sample. This means that the Yanomami microbiome sample is extremely unique but microbiomes within that sample are very similar, this is most likely due to the Yanomami leading vastly different lifestyles than Western societies and individuals in the village being in extremely close quarters with each other (eating the same food, drinking from the same water source, no waste removal, etc.).Continue reading “Which came first, antibiotics, or antibiotic-resistance? A study of Uncontacted Amerindians.”
Background: In 2012 periodontal disease affected 46% of adults in the United States, with 8.9% classified as severe (Eke et al. 2015). Before everyone starts freaking out and drinking mouthwash, let’s talk about periodontal disease. Periodontal disease means gum disease, anything from simple gum inflammation, all the way to the loss of bone and the teeth falling out (“Periodontal Gum Disease’, 2013). Below I included a figure to show the progression of the disease.
Normal progression of periodontal disease from healthy to severe periodontitis (Gromadzki)
This disease is caused by microbes in the dental plaque migrating into the gum pockets causing inflammation, which will cause the gum to recede and with it the connective tissue holding in the tooth (Teles et al. 2013). Since periodontal disease is caused by microbes, it would not be surprising if there were differences between the community of microbes living in the mouths of healthy individuals, and those with periodontal disease. For the purpose of this discussion the oral microbiome is referring to the community of bacteria in the mouth of an individual. In fact, with the use of next-gen sequencing of the oral microbiome, it may be possible to determine differences between the mircobiomes of healthy and diseased individuals. A 2012 study found that community diversity is higher in individuals with chronic periodontal disease, but the results were complicated with 123 species were more abundant in diseased individuals and with 53 species were more abundant in healthy individuals (Griffen et al. 2012).Continue reading “Can the Oral Microbiome indicate Periodontal Disease State?”
Genetics and the environment; how do these interact? Do they always interact, or do genetics sometimes overrule characteristics learned from our environment? The question of nature, generally thought of to be our genetic make-up, versus nurture, the environments we’re exposed to in our developmental years, has been the topic of debate by scientists and philosophers for centuries. Yet, the definitive answer still frustratingly eludes us. Some things, like the number of limbs we’re born with, are entirely decided by genetic factors. Other things, like many of our behaviors, rely on an interaction between genetics and developmental environment. Continue reading “The Human Salivary Microbiome: Where the environment trumps genetics”
