Distinct composition and distribution of the gastric mycobiota observed between dyspeptic and gastric cancer patients evaluated from gastric biopsies

Abstract

Objectives: In recent years, studies have proved that the stomach is not sterile as previously believed and thereby harbors a unique gastric microbiota. Since most studies have investigated the bacterial composition of the gastric microbiota, the investigation of other microorganisms is still in its infancy. To date, the fungal composition of the stomach (the gastric mycobiota) has gained more attention in microbiota studies. Nevertheless, there is a lack of studies investigating the gastric mycobiota and the association to the pathogenesis of gastric diseases. We aim to investigate the composition of the gastric mycobiota of patients diagnosed with dyspepsia or gastric cancer and define the persistent and transient fungal colonizers of the stomach. Patients and Methods: Gastric biopsies from twenty-two patients diagnosed with dyspepsia and twelve patients diagnosed with gastric cancer were analyzed by 18S rDNA sequencing to compare the gastric mycobiota. The gastric biopsies were either unwashed or washed to distinguish fungal adherence. To compare the mycobiota from cancer tissue and normal tissue, the gastric biopsies from gastric cancer patients were taken from two sites; antrum (AN) and corpus from cancer area (CA). Results: The distribution and composition of the gastric mycobiota in gastric cancer and dyspeptic patients were significantly distinct. The most prominent difference was observed in the relative abundance of the fungal genus Malassezia as it was significantly increased in gastric cancer patients. Malassezia is an opportunistic pathogen, which has been shown to promote the formation of several cancer types. Thereby the results in this study indicate that Malassezia may play a role in the formation of gastric cancer, however, further investigation is needed. Conclusions: The results from this study show that the gastric mycobiota might has an important role for the pathogeneses of human gastric diseases, as significant changes in the gastric mycobiota are observed in gastric cancer patients compared to dyspeptic patients. This advocates more research within the role of gastric mycobiota as more knowledge can lead to new therapeutics.

Keywords

• fungi
• mycobiota
• stomach
• gastric microbiota
• gastric biopsies
• gastric cancer
• dyspepsia.