Periodontal health is shaped by a complex microbial community, not by a single bacterium.
Your mouth is home to hundreds of microbial species that live together in constantly changing communities. Some microorganisms are commonly found in healthy mouths, while others have been extensively studied in connection with periodontal microbial communities. Among the bacterial targets frequently investigated in periodontal research are Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Aggregatibacter actinomycetemcomitans, and Prevotella intermedia.
These five organisms represent selected targets with a substantial history in periodontal microbiology and molecular research. But understanding them requires looking beyond individual bacteria and considering the communities in which they exist.
It’s About the Community, Not Just the Bacterium
Periodontal microorganisms do not live in isolation. They interact with one another and with the host environment, forming complex microbial communities.
One of the most influential frameworks in periodontal microbiology came from Socransky and colleagues, who grouped subgingival bacteria into microbial complexes based on their patterns of association.
The best-known is the Red Complex, which includes:
- Porphyromonas gingivalis
- Tannerella forsythia
- Treponema denticola
Other microorganisms have been grouped into additional microbial complexes, including the Green Complex, Orange Complex, and Purple Complex.
These classifications helped researchers move beyond the idea of looking at one microorganism at a time and toward understanding the oral microbiome as a dynamic microbial ecosystem. The periodontal microbiome is a community, not a checklist of individual bacteria.
Five Bacterial Targets with a Long History of Research
Porphyromonas gingivalis - A Red Complex Member
P. gingivalis is one of the most extensively studied microorganisms in periodontal research. It is a member of the Red Complex and has been investigated extensively for its interactions with other microorganisms and the host environment. Its established role in periodontal microbiology has made it a frequent target in molecular research and periodontal microbial testing.
Tannerella forsythia - A Red Complex Member
T. forsythia is another member of the Red Complex and has been widely studied as part of subgingival microbial communities. Research has examined its presence and relationships within complex microbial communities associated with periodontal health and disease.
Treponema denticola - A Red Complex Spirochete
T. denticola is a spirochete and the third member of the classic Red Complex. Its distinctive biology and interactions with other microorganisms have made it an important subject of periodontal microbiology research. Together, P. gingivalis, T. forsythia, and T. denticola form the classic Red Complex described in the Socransky microbial-complex framework.
Aggregatibacter actinomycetemcomitans - A Distinct Periodontal Target
A. actinomycetemcomitans has received considerable attention in periodontal research, particularly in studies involving certain periodontal disease patterns and populations. It is not a member of the classic Red Complex, and its distribution and clinical significance can vary depending on the population and clinical context.
Prevotella intermedia - An Orange Complex Member
P. intermedia is an anaerobic bacterium that has been extensively studied in periodontal microbiology and is associated with the Orange Complex in the Socransky classification. Its presence within complex microbial communities has been investigated in relation to periodontal health and disease, making it another well-established target in periodontal microbial research.
Why Look at More Than One Target?
If the oral microbiome is a community, examining a single microorganism provides only one piece of the picture. Testing multiple selected targets can provide a broader microbial profile, showing which targets are detected and, when quantitative methods are used, the measured levels of those targets. At the same time, more targets do not automatically mean more useful information. Expanding a panel can introduce additional assay, validation, interpretation, and reporting considerations.
That raises an important question:
How do you choose the targets that provide meaningful information without simply measuring everything?
That question is at the heart of targeted molecular testing—and it is one we will explore later in this article.
From “Is It There?” to “How Much Was Measured?”
There is another important distinction in molecular testing: detection versus quantification.
A qualitative test essentially asks:
Was this microorganism detected?
A quantitative test goes one step further:
What level of this microorganism was measured?
Two samples may both have the same bacterial target detected while having very different measured quantities. Quantitative information can therefore add another layer of context to a microbial profile.
This is where multiplex quantitative PCR (qPCR) becomes particularly useful. Multiple selected bacterial targets can be evaluated in the same reaction using target-specific fluorescent probes, allowing their measured quantities to be determined simultaneously.
The UniquePerioSignature™ Approach
The UniquePerioSignature™ Panel uses a focused, quantitative molecular approach to identify and quantify selected periodontal bacterial targets from a saliva sample. The goal is not to measure every microorganism in the oral microbiome.
“It is to focus on selected, well-studied bacterial targets and generate quantitative information that can be considered alongside clinical findings and other relevant patient information.”
And that leads to the next important question:
If more bacteria can be measured, why focus on five?
That is where the science and the philosophy behind UniquePerioSignature™, gets interesting.
References
- Socransky SS, Haffajee AD, Cugini MA, Smith C, Kent RL Jr. Microbial complexes in subgingival plaque. Journal of Clinical Periodontology. 1998;25(2):134–144. doi:10.1111/j.1600-051X.1998.tb02419.x.
- Haffajee AD, Cugini MA, Tanner A, Pollack RP, Smith C, Kent RL Jr, Socransky SS. Subgingival microbiota in healthy, well-maintained elder and periodontitis subjects. Journal of Clinical Periodontology. 1998;25(5):346–353. doi:10.1111/j.1600-051X.1998.tb02454.x.
- Socransky SS, Haffajee AD. Periodontal microbial ecology. Periodontology 2000. 2005;38(1):135–187. doi:10.1111/j.1600-0757.2005.00107.x.
- Hajishengallis G, Lamont RJ. Breaking bad: manipulation of the host response by Porphyromonas gingivalis. European Journal of Immunology. 2014;44(2):328–338. doi:10.1002/eji.201344202.
- Curtis MA, Diaz PI, Van Dyke TE. The role of the microbiota in periodontal disease. Periodontology 2000. 2020;83(1):14–25. doi:10.1111/prd.12296.
- Boutaga K, van Winkelhoff AJ, Vandenbroucke-Grauls CMJE, Savelkoul PHM. Periodontal pathogens: a quantitative comparison of anaerobic culture and real-time PCR. FEMS Immunology & Medical Microbiology. 2005;45(2):191–199. doi:10.1016/j.femsim.2005.03.011.