Periodontal Microbiology
Periodontal disease has been linked to the growth of specific bacterial species with the patients. These bacteria seem to be carried by those patient who have periodontitis and not by the rest of the human population.
Acquisition of our Oral Bacteria
We all acquire a set of bacteria from our environment within the first weeks of life. These bacteria come from the people we have a high level of contact with in these first months of life. In other words, the source of our oral bacteria is from the mouths of our parents. It appears that we adapt to these early colonizing bacteria by not developing antibody responses to them, which means we will most likely become carriers of them for the rest of our lives. It appears that the bacteria we carry seem to be responded too much in the same way as our own cells – no response.
The classic case of a person who acquired and carried bacteria which caused infections of others was the unfortunate Typhoid Mary. This is an extreme case but shows that all of us may carry bacteria which can cause infections not only in ourselves but also in others.
Periodontal causing Bacteria
There appears to be several clusters of bacteria involved in the progression of periodontal disease. There is one group termed the Red Complex Bacteria and these are Porphyromonas gingivalis, Tannerella forythia and Treponema denticola. A second set of bacteria termed Orange Complex Bacteria also seem to play a role in the disease. Of these bacteria one named Fusobacterium nucleatum seems to be important.
Research at the University of Melbourne has found that the production of toxin materials by these bacterial species correlates with disease progression. Unexpectedly we also found that Fusobacterium nucleatum appears to play a role in conversion of the lesion from health toward progression. The rapid growth of the red complex bacteria along with elevated toxin production by these bacteria appeared to be the best predictor of increased disease progression (Wong et al 2015).
Red Complex Bacteria
Porphyromonas gingivalis is found in the oral cavity, the upper gastrointestinal and respiratory tracts and in the bowel. It has been shown that P. gingivalis can invade human epithelial (skin) and connective tissue cells and can survive within the cells even in the presence of considerable concentrations of antibiotics. In addition, P. gingivalis has been linked to Rheumatoid Arthritis, which interestingly has been linked to an increased incidence of periodontal disease. Treatment of periodontal disease has been associated with a reduction of the symptom severity in patients with Rheumatoid arthritis. P. gingivalis is able to evade the host immune response and this allows it to cause the disease.
P. gingivalis has been associated with increasing the virulence of other bacteria within the Red Complex bacteria. Components from P. gingivalis were found to be necessary for the invasion of epithelial cells by Tannerella forsythia. P. gingivalis in conjunction with Treponema denticola seem necessary to induce bone loss around the teeth.
Preliminary evidence suggests that both P. gingivalis and F nucleatum levels increase in patients with hypothyroidism and this seems to be due to a fall in available iodine which is used in an enzyme system used to kill these bacteria by certain white blood cells. (Wei et al 2017).
Orange Complex Fusobacterium nucleatum
Fusobacterium nucleatum is commonly recovered from periodontal plaque and we found in a University of Melbourne study that when it produces a certain toxin it was associated with increased bone loss around the teeth. It had not been previously found to be associated with this clinical outcome. This suggests that this bacteria may have more to do with periodontal disease than previously thought.
Aggregatibacter actinomycetemcomitans
Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans) is a bacteria that has been linked to a localized form of periodontitis. It has an interesting way of evading the host immune response. It produces small vesicles which it sheds from its surface, which when ingested by the white bloods cells which normally ingest and kill bacteria results in them dying before they can kill the bacteria itself.
Testing and Treatment
At this point in time we do not have good or simple tests to determine the bacterial presence within your mouths. The University of Melbourne along with CSL are in the process of developing a vaccine against P. gingivalis and when this becomes available it may provide us with an additional treatment method for the more severe forms of periodontitis.
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