Periodontitis Revisited: It’s the Community, Not Single Microorganisms!

There’s a direct correlation between the diversity of your oral microbiome – the up to 700 different species of bacteria that live in your mouth – and the health of your teeth, according to a study from scientists at the University of Münster and Bielefeld University.

Some combination of those bacteria, it’s not clear which ones exactly, are a key component responsible for periodontitis, a disease that weakens the supporting tissues of your teeth and can cause them to loosen and eventually fall out. Periodontitis is one of the most common diseases in the world and half of the people over 40 years old in developed countries have it.

Traditionally the treatment for periodontitis is scaling and root planning, or SRP – a dentist scraping away the plaque from teeth pockets that causes the disease to start. Antibiotics are commonly prescribed as well, though just how well they work is not clear. The goal of the study was to see how bacteria react to treatment. This is the first step toward understanding the true impact treatments are having and eventually developing a prognostic tool to monitor the progression of the disease.

What the team found was that successful treatment, whether from SRP alone or SRP and antibiotics, resulted in a higher diversity of the species of bacteria and their abundance living in the patient’s mouth. Traditionally scientists have tried to monitor the disease by looking at just a few bacteria at a time, which they either grew in petri dishes – an approach dating back to the time of Robert Koch – or detected by molecular means. It’s an approach that study author Dr. Dag Harmsen, a researcher from the Department for Periodontology at the University of Münster, says is ineffective.

“Periodontitis is not caused by individual micro-organisms, you need to look at all the bacteria in the entire oral microbiome and see how the entire population shifts to understand if a treatment is having an effect,” said Harmsen.

Harmsen’s approach of looking at an entire population of organisms is called amplicon metagenomics. It allows researchers to simply sequence the DNA of every organism that is present in a sample and see what the data tells them, rather than approaching the experiment with a thesis that could limit what they can find. These researchers were the first to publish metagenomic research on the Ion PGM™ sequencer, a new sequencing technology that makes metagenomic sequencing faster and more affordable than in the past.

“The biggest challenge with NGS experiments in general is to deal with the huge amount of data generated in the proper way. Here especially it was an endeavor to implement an automated analysis pipeline for such a new technology platform,” explained the first author of the PLoS ONE publication Sebastian Jünemann, a bioinformatician from the Institute for Bioinformatics, Center for Biotechnology, Bielefeld University.

“If the study results are confirmed in further experiments with larger sample size, the detected changes in community profiles and metrics will be a very useful diagnostic prognostic factor for treatment success and certainly be applied soon in routine patient care,“ added Harmsen.

Citation:
Jünemann S, Prior K, Szczepanowski R, Harks I, Ehmke B, Goesmann A, Stoye J, Harmsen D (2012) Bacterial community shift in treated periodontitis patients revealed by Ion Torrent 16S rRNA gene amplicon sequencing. PLoS ONE 7(8): e41606.

doi: 10.1371/journal.pone.0041606

Contact:
Dr. Thomas Bauer
University of Münster, Medical Faculty
Tel.: 0251 / 83-58937
E-mail: thbauer@uni-muenster.de