Study sheds new light on the link between oral bacteria and disease

mouth of the gum

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Researchers from the Karolinska Institutet in Sweden have identified the bacteria most commonly found in severe oral infections. Few such studies have been done before, and the team now hopes that the study can provide deeper insight into the link between oral bacteria and other diseases. The study is published in Microbiological spectrum.

Previous studies have shown clear links between oral health and common diseases such as cancer, cardiovascular disease, diabetes and Alzheimer’s disease. However, there have been few longitudinal studies identifying which bacteria are present in infected oral and maxillofacial areas. Researchers at the Karolinska Institutet have now analyzed samples taken between 2010 and 2020 at the Karolinska University Hospital in Sweden from patients with severe oral infections and created a list of the most common bacteria.

This was a joint study conducted by Professor Margaret Sällberg Chen and Professor Volkan Özenci’s research group.

“Here we report for the first time the microbial composition of bacterial infections from samples collected over ten years in Stockholm County,” says Professor Sällberg Chen from the Department of Dentistry Karolinska Institutet. “The results show that several bacterial infections associated with systemic diseases are constantly present and some have even increased over the last ten years in Stockholm.”

Role in other diseases

The study shows that the most common bacterial strains among the samples were Firmicutes, Bacteroidetes, Proteobacteria and Actinobacteria, while the most common genera were Streptococcus spp., Prevotella spp. and Staphylococcus spp.

“Our results provide new insight into the diversity and prevalence of harmful microbes in oral infections,” says Professor Sällberg Chen. “The finding is not only important for dentistry, but also helps us understand the role of dental infection in patients with underlying disease. If a certain bacterium infects and causes damage in the mouth, it is very likely that it can be harmful to tissues elsewhere in the body, as the infection spread.”

The research group has previously shown that the presence of oral bacteria in the pancreas reflects the severity of pancreatic tumors.

A useful method in dental care

The study was conducted using 1,014 samples from as many patients, 469 of whom were women and 545 men, and using a mass spectrometric method called MALDI-TOF, which quickly identifies the individual live bacteria in a sample but is rarely used in dental care.

“Our study was a single-center epidemiological study, and to ensure the validity of the results, we need to conduct further and larger studies,” says Volkan Özenci from the department of laboratory medicine at Karolinska Institutet. “We now hope that dentists will work more closely with clinical microbiology laboratories to better understand the bacteria that cause dental infections in order to improve the diagnosis and therapeutic management of oral infections.”

The study is part of Khaled Al-Manei’s doctoral thesis, the next step of which is a similar epidemiological study of fungal infections in the mouth, which aims to identify new fungi and microbes and understand what causes their possible malignancy.

More information:
Volkan Özenci et al., Clinical microbial identification of severe oral infections by MALDI-TOF mass spectrometry in Stockholm County: an 11-year (2010-2020) epidemiological survey, Microbiological spectrum (2022). DOI: 10.1128/spectrum.02487-22

Provided by Karolinska Institutet

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