Table 2.

Summary of studies examining the relationship between gastric cancer and microbiota diversity.

Reference	Study Design	Sample Size	Subject Country of Origin	Sample Type	Sequencing Methods	Outcomes	Major Findings
Dicksved18	Case-control	10 GC patients, 5 dyspeptic controls	Sweden	Gastric biopsies from antrum and corpus	T-RLFP, 16S rRNA gene sequencing	Microbial composition of GC patients compared to controls	No significant difference between microbial composition of gastric cancer patients compared to controls
Wang19	Case-control	103 GC patients, 212 chronic gastritis controls	China	Gastric biopsies from antrum or within 5 cm of cancerous lesion	16S rRNA pyrosequencing	Bacterial load of gastric mucosa; Biodiversity, composition, structure of microbiota	↑ Bacterial load in GC patients ↑ Lactobacillus, Escherichia-Shigella, Nitrospirae, Burkholderia fungorum in GC patients No significant difference in diversity index between GC and chronic gastritis
Aviles-jimenez20	Case-control	5 GC patients, 5 IM patients, 5 nonatrophic gastritis patients	Mexico	Gastric biopsies from antrum in non-cancer patients, biopsies from lesion in GC patients	G3 PhyloChip 16S rRNA microarray	Gastric microbiota diversity; Taxa abundance differences between groups	↓ bacterial diversity in GC patients compared to IM and gastritis patients ↑ Lactobacillus coleohominis and Lachnospiraceae in GC patients
Coker21	Case-control	20 GC, 17 IM, 23 AG, 21 superficial gastritis patients	China	Gastric biopsies from antrum, body, fundus for non-cancer patients; Biopsies from lesion in GC patients	16s rRNA gene sequencing via Mothur software	Microbial diversity and richness	↓ bacterial diversity and richness in GC and IM patients compared to AG and superficial gastritis Overrepresentation of oral flora in GC, particularly P. stomatis, S. exigua, P. micra, S. anginosus and D. pneumosintes
Ferreira22	Case-control	54 GC, 81 chronic gastritis patients	Portugal	Gastric biopsies or surgical specimens (non-neoplastic tissue adjacent to tumor only)	16S rRNA next generation sequencing via ION PGM	Gastric microbial diversity	↓ gastric microbial diversity in GC ↓ H. pylori abundance in GC ↑ presence of bacteria with nitrate reductase and nitrite reductase functions
Eun23	Case-control	11 GC, 10 IM, 10 chronic gastritis patients	Korea	Gastric biopsies from antrum and corpus (non-neoplastic tissue adjacent to tumor only)	16S rRNA gene sequencing using high throughput sequencing platform, 454 GS FLX Titanium	Diversity of gastric microbiota	↑ microbial diversity in GC group compared to IM and gastritis ↑ abundance of Streptococcus, Lactobacillus, Veillonella, and Prevotella in GC
Castaño-Rodriguez24	Case-control	12 GC, 20 functional dyspepsia patients	Singapore and Malaysia	Gastric biopsies from antrum	16S rRNA gene sequencing using Illumina MiSeq	Gastric microbiota richness and phylogenetic diversity	↑ microbial richness and phylogenetic diversity in GC patients ↑ Lactococcus, Lactobacillus, Veilonella, and Fusobacteriaceae taxa in GC patients
Hu25	Case-control	6 GC, 5 chronic gastritis patients	China	Gastric wash samples	Shotgun metagenomic sequencing	Gastric microbiota richness and relative bacterial abundance	↑ Neisseria, Alloprevotella, Aggregatibacter, Porphyromonoas endodontalis, Streptococcus mitis in GC ↓ Sphingobium yanoikuyae in GC
Park26	Case-control	55 GC, 19 IM, 62 chronic gastritis patients	Korea	Gastric biopsies from antrum	16S rRNA gene sequencing using Illumina MiSeq	Relative bacterial abundance	↑ Rhizobiales in IM compared to gastritis ↑ Cyanobacteria in H. pylori negative chronic gastritis patients

GC, gastric cancer; IM, intestinal metaplasia; AG, atrophic gastritis.