Study sheds new light on link between oral bacteria and disease

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

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

This was a collaborative study by Professor Margaret Sällberg Chen and Assistant Professor Volkan Özenci’s research groups.

“We report here, for the first time, the microbial composition of bacterial infections from samples taken over a ten-year period in Stockholm County,” says Professor Sällberg Chen from the Department of Dentistry at Karolinska Institutet. “The results show that several bacterial infections linked to systemic diseases are constantly present and some have even increased over the last decade in Stockholm.”

A role in other diseases

The study shows that the most common bacterial phyla 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 discovery is not only important for dentistry, it also helps us understand the role of dental infection in patients with underlying diseases. If a certain bacterium infects and causes damage in the mouth, it is very likely that it could harm tissues elsewhere in the body as the infection spreads.”

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

Useful method in dental care

The study was conducted using 1,014 samples from as many patients, including 469 women and 545 men, and a mass spectrometry method called MALDI-TOF that quickly identifies individual live bacteria in a sample, but which 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 do more and larger studies,” says Volkan Özenci from the Department of Laboratory Medicine at Karolinska Institutet. “We now hope that dentists will collaborate more with clinical microbiology laboratories to better understand the bacteria responsible for dental infections, improve the diagnosis and the 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 that aims to identify new fungi and microbes and understand the causes of their possible malignancy.