Research Of Salivary Microbiota In Patients With Functional Dyspepsia

ObjectiveThe aim of this study was to analyse and compare the difference of salivary microbiota between functional dyspepsia(FD)patients and healthy controls(HC).We also aimed to explore whether different subtypes of FD and anxiety status would have an effect on the composition of the salivary microbiota.Finally,we hoped to find out the unique bacterium related to different diseases or status.MethodsSaliva samples were collected from 68 FD patients and 47 HCs.Every subject filled in the Generalized anxiety disorder-7(GAD-7)scale and scores were calculated.According to the ROME III criteria and GAD-7 score,40 FD patients,including 20 postprandial distress syndrome(PDS)and 20 epigastric pain syndrome(EPS)patients were selected.Another 40 FD patients,including 20 anxiety-positive FD(FD.P)and 20 anxiety-negative FD(FD.N)were selected.20 HC were selected,too.Whole genomic DNA of all the samples was extracted,and Illumina high-throughput sequencing technology was used to sequence the 16S rRNA-V4 hypervariable region of all microbiomes in all samples.Subsequently,all the datas were sequenced by the Illumina HiSeq2500 platform.Qulified sequences were analysed with the QIIME software.Datas include operational taxonomic units(OTUs),Alpha diversity and Beta diversity etc.Alpha diversity indices,including Chaol,ACE,Shannon and Simpson,were used to analyse the bacterial abundance and diversity.Beta diversity indices were used to compare bacterial community structure.All the subjects were confirmed Helicobacter pylori(Hp)negative,using 13/14C-urea breath test and rapid urease test.ResultsThe salivary microbiota in FD patients was dominated by Proteobacteria,Bacteroidetes and Fusobacteria in the phylum level.In the genus level,the salivary microbiota in FD patients was dominated by Neisseria,Fusobacterium and Prevotella.The salivary microbiota composition was similar in PDS group,EPS group,FD.P group and FD.N group.To put it simply,the salivary bacterium in the above groups were dominated by Proteobacteria,Bacteroidetes,Neisseria and Fusobacterium in different taxonomic levels.The Alpha diversity indices,namely Chao1,ACE,Shannon and Simpson,indicated that the microbiota abundance and diversity in different groups were both reasonable and balanced.The results were the same using other indices,such as good's coverage,rarefaction curve and rank abundance curve.However,considering the above Alpha indices,the difference between FD patients and HCs was not significant.The differences were also not significant between PDS group and HCs,EPS group and HCs,PDS group and EPS group.The microbiota abundance in FD.P group was significantly lower than FD.N group and HCs,but there was no significant difference of diversity among the above groups.The linear discriminant analysis effect size tool(LEfSe)was used to screen different bacterium in all taxonomic levels between the case and control groups.There were thirteen kinds of microbiota with significant difference using LEfSe,including Bacteroidetes;Baceroidales;Bacterodia;Prevotella;Negativicutes;Selenomonadales;Vei llonellaceae;Veillonella;Pasteurellaceae;Pasteurellales;Gammaproteobacteria;Betaprot eobacteria;Proteobacteria.Five kinds were enriched in FD group.Gammaproteobacteria;Pasteurellaceae and Pasteurellales were the unique microbiota between PDS group and EPS group,but only enriched in PDS group.There were eight kinds of microbiota with significant difference between PDS and HC,including Proteobacteria;Gammaproteobacteria;Pasteurellaceae;Pasteurellales;Betaproteobacteria;Bacteroidetes;Baceroidales and Bacterodia.F ive kinds of microbiota dominated in the PDS group.There were seven kinds of microbiota with significant difference between EPS group and HC,including Baceroidales;Bacterodia;Negativicutes;Selenomonadales;Veillonella;Veillonellaceae;Prevotella,but only enriched in HC.There were thirteen kinds of microbiota with significant difference between FD.N group and HC,namely Bacteroidetes;Baceroidales;Bacterodia;Prevotella;Negativicutes;Selenomonadales;Veillonellaceae;Pasteurellaceae;Pasteurellales;Gammaproteobacteria;Betaproteobacteria and Proteobacteria.Five kinds of microbiota were enriched in FD.N group.There were four kinds of microbiota with significant difference between FD.P group and HC,including Baceroidales;Bacterodia;Streptococcaceae and Streptococcus.Streptococcaceae and Streptococcus were enriched in FD.P group.However,there was not any microbiota with significant difference between FD.P group and FD.N group.ConclusionComparing to HC,the salivary microbiota in FD patients was dominated by Proteobacteria in the phylum level.The salivary microbiota in HC was dominated by Bacteroidetes.Different subtypes of FD patients had its unique microbiota.The unique microbiota in PDS group included Proteobacteria,Gammaproteobacteria,Pasteurellaceae and so on.There were no unique microbiota in the EPS group.Streptococcaceae,Streptococcus were the characteristic bacterium in FD.P group.The characteristic bacterium in FD.N group included Proteobacteria,Gammaproteobacteria,Betaproteobacteria,Pasteurellaceae and Pasteurellales.These results suggested the relationship between microbiota and clinical symptoms and mood status in FD patients.