Researchers find link between oral bacteria and stomach cancer

stomach cancer
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Elevated pathogen colonisation and a lack of bacterial diversity in the mouth were identified in people with precancerous lesions that could precede stomach cancer, a new US study has found.

The findings are published in the November issue of the Journal of Periodontology.

Although some risk factors—such as H. pylori colonisation, cigarette smoking, and eating salt and preserved foods—are known to contribute to the development of stomach cancer, many new cases unrelated to these risk factors are diagnosed each year.


Scientists have hypothesised that a group of pathogens may be responsible for causing periodontal disease and the resulting chronic systemic inflammation that may contribute to the development of gastric cancer.

This study, by researchers from New York University College of Dentistry and New York University School of Medicine, assesses the association between periodontal pathogen colonisation and the potential risk of developing precancerous lesions that may predict stomach cancer.

The team studied 105 individuals scheduled to receive an upper endoscopy. After the endoscopic procedure and histopathologic evaluation, 35 people were diagnosed with precancerous lesions of gastric cancer while another 70 people of similar age without precancerous lesions were included in the study as a control group.

The researchers then performed full-mouth examinations to assess participants’ periodontal conditions. Saliva and dental plaque samples were collected to evaluate colonisation by several pathogens and to characterise oral microbial diversity.

Compared with the control group, patients with precancerous lesions experienced higher prevalence of bleeding when probed, higher levels of two pathogens (T. denticola and A. actinomycetemcomitans), and less bacterial diversity in their saliva.

A further analysis, which took into account socio-demographic factors, oral health behaviours, and periodontal assessments, revealed additional predictors of precancerous lesions: elevated colonisation of three pathogens (and aforesaid two and T. forsythia), decreased bacterial diversity in dental plaque, and not flossing regularly.

The researchers concluded that the colonisation of periodontal pathogens and the alternated bacterial diversity in the oral cavity are important factors that, when at higher or lower levels respectively, may contribute to an increased risk of developing precancerous gastric lesions.

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