title: Bacterial overgrowth and diversification of microbiota in gastric cancer.
abstract: OBJECTIVE
  Microbiota is potentially linked to the development of cancer. However, the features of microbiota in gastric cancer remain unclear. The aim of this study was to characterize the gastric microbiota in cancer.
  
  
  METHODS
  A total of 315 patients, including 212 patients with chronic gastritis and 103 patients with gastric cancer, were enrolled in the study. The bacterial load of gastric mucosa was determined using quantitative PCR. To analyze the biodiversity, structure, and composition of microbiota, amplicons of the 16S rRNA gene from 12 patients were pyrosequenced. The sequences were processed and subsequently analyzed.
  
  
  RESULTS
  The amount of bacteria in gastric mucosa was estimated to be 6.9×10 per gram tissue on average. It was higher in Helicobacter pylori-infected patients (7.80±0.71) compared with those uninfected (7.59±0.57, P=0.005). An increased bacterial load up to 7.85±0.70 was detected in gastric cancer compared with chronic gastritis (P=0.001). The unweighted principal coordinate analysis showed that the structure of microbiota in gastric cancer was more diversified. Five genera of bacteria with potential cancer-promoting activities were enriched in gastric cancer. The weighted principal coordinate analysis showed that the presence of Helicobacter pylori markedly altered the structure of microbiota, but had little influence on the relative proportions of the other members in the microbiota.
  
  
  CONCLUSIONS
  Findings from this study indicated an altered microbiota in gastric cancer with increased quantity of bacteria, diversified microbial communities, and enrichment of bacteria with potential cancer-promoting activities. These alterations could contribute toward the gastric carcinogenesis.
authors.affiliation: aDepartment of Central Laboratories and Gastroenterology, Qingdao Municipal Hospital bDepartment of Gastroenterology, the Affiliated Hospital of Qingdao University, Qingdao, China.
authors.forename: Lili
authors.initials: L
authors.lastname: Wang
authors.forename: Jianhua
authors.initials: J
authors.lastname: Zhou
authors.forename: Yongning
authors.initials: Y
authors.lastname: Xin
authors.forename: Changxin
authors.initials: C
authors.lastname: Geng
authors.forename: Zibin
authors.initials: Z
authors.lastname: Tian
authors.forename: Xinjuan
authors.initials: X
authors.lastname: Yu
authors.forename: Quanjiang
authors.initials: Q
authors.lastname: Dong
mesh_terms: D000328:Adult; D000368:Aged; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification; D058491:Bacterial Load; D002908:Chronic Disease; D004269:DNA, Bacterial / Q000235:genetics; D064806:Dysbiosis; D005260:Female; D005753:Gastric Mucosa / Q000382:microbiology*; D005756:Gastritis / Q000175:diagnosis / Q000382:microbiology*; D000069196:Gastrointestinal Microbiome; D016480:Helicobacter pylori / Q000254:growth & development; D006801:Humans; D008297:Male; D008875:Middle Aged; D021521:Ribotyping; D012307:Risk Factors; D013274:Stomach Neoplasms / Q000175:diagnosis / Q000382:microbiology*
chemical_list: D004269:DNA, Bacterial