Study On The Relationship Between Characteristics Of Gut Microbiome And Clinical Infection In Acute Myeloid Leukemia Patients

Objective:Gut microbiota plays an important role in maintaining intestinal barrier function and regulating the body’s immunity.During induction chemotherapy in patients with malignant haematological diseases,disturbed gut microbiota may translocate through the damaged intestinal mucosa to the blood or other organs,or affect immune regulation,leading to the development of infections.It is still unclear whether gut microbiota can predict the occurrence of infection during myelosuppression in Chinese patients with acute myeloid leukemia(AML).Aims:(1)to reveal the characteristics of gut microbiota in AML patients who developed clinical infection and non-infection;(2)to observe the changes of gut microbiota during induction chemotherapy and then analyze their relationship between the site of infection(bloodstream,lung)and the occurrence of mucositis during the post-chemotherapy myelosuppression period;(3)to identify markers of gut microbiota that predict the occurrence of infections in AML patients,followed by functional prediction of the screened differential flora.Methods:This study was a prospective clinical trial(NCT05016752)that included 58 AML patients who received induction or re-induction therapy at the Department of Hematology,The First Affiliated Hospital of Soochow University from August 2021 to October 2022.Stool samples were collected before chemotherapy,after the 7th,14th and 21st day of chemotherapy,the flora were isolated,DNA was extracted,the 16S rRNA V4 regions were amplified by polymerase chain reaction(PCR),and basic biological information was obtained by high-throughput sequencing.qiime2 software combined with clinical information was used to analyze the structural characteristics of the microecological community in each group of patients treated with chemotherapy,and Lefse analysis was performed to select species markers.PICRUSt analyzed the abundance of metabolic pathways in each group of patients and correlated the differential genera analyzed by metagenomeSeq with individual functional metabolic differences by spearman rank correlation.In summary preliminary exploration of the relevance of intestinal genera to the occurrence of clinical infections.Results:1.Clinical characteristics of infections in AML patients undergoing induction chemotherapy:a total of 58 AML patients were included in this study.The overall incidence of infection was 60.3%(35/58),25.9%(15/58)of bloodstream infections,37.9%(22/58)of pulmonary infections,22.4%(19/58)of mucositis,and 32.8%(19/58)of moderate-to-severe diarrhea.The incidence of initial neutrophil count<0.5×109/L,neutrophil deficiency with fever,mucositis,and diarrhea was higher than the noninfected patient group.The clinical remission rate of the disease was lower in the infected group than in the non-infected group,and the recovery time of routine blood trilineage cells was significantly longer than in the non-infected group(P<0.05 above).2.Blood macrogenome sequencing was more efficient than blood culture in detecting bloodstream infections.The diversity of gut microbiota before chemotherapy predicted the occurrence of bloodstream infections,and there were differences in the composition of gut microbiota with different strains of bloodstream infections.The positive rate of blood macrogenome sequencing in our hospital was 87.69%(228/260 cases).The main pathogens detected in bloodstream infections were Klebsiella pneumoniae(4 cases),Enterobacteriaceae(4 cases)and Pseudomonas aeruginosa(2 cases),with 4 cases detected in advance by blood macrogenome sequencing and 7 cases detected by complementary negative blood culture results.The baseline gut microbiota Shannon index was lower in patients with bloodstream infection than in the noninfected group(P=0.0394),and the ROC curve results suggested that when the Shannon index was<3.967,it could predict the occurrence of bloodstream infection to some extent(AUC=0.7386,P=0.0232).The baseline gut microbiota of patients with Klebsiella pneumoniae infection showed a high abundance of Proteobacteria(RA≥25%)and a low abundance of Actinobacteria(RA ≤0.1%),and the stools of patients with Enterobacter infection showed a very high abundance of Firmicutes(RA≥ 84%)and a low abundance of Bacteroidetes(RA≤0.01%).3.The composition of gut microbiota and the differential genera of the biomarkers differed between the infected and non-infected groups at different periods.Before treatment,patients in the infected group showed higher abundance of the Proteobacteria and Actinobacteria,and Enterobacter of Bacilli was dominant.Both groups showed an increase in Proteobacteria,a decrease in Firmicutes and Bacteroidetes during chemotherapy.The infected group showed a statistically significant increase in the relative abundance of Proteobacteria(12.8%vs.43.9%,P<0.001),a decrease in the relative abundance of Firmicutes(51.7%vs.25.9%,P=0.009),and a decrease in the relative abundance of Bacteroidetes(30.3%vs.8.9%,P=0.027).While in postchemotherapy infection,the phylum level was dominated by proteobacteria and Actinomycetes,and the genus level showed dominance of Bifidobacterium,Prevotella,Roseburia,Subtilis thermophilus,Microbacterium,and Staphylococcus.4.The MetaCyc metabolic pathway showed enhanced nucleotide metabolism and methanol metabolism in the infected group compared to the non-infected group.Differential pathways of intestinal metabolism showed enhanced metabolism of mannose,galactose and arginine.The relative abundance of Dietzia,Ochrobactrum and Halomonas was higher than the non-infected group after chemotherapy.Among them,the differential metabolic pathway positively associated with Dietzia was associated with anti-inflammatory response and epidermal mucosal repair,and the differential metabolic pathway positively associated with the catabolism of tryptophan in the latter two.5.There were different clusters of gut microbiota in patients with different sites of infection.The bloodstream infection group was mostly of the phylum Proteobacteria,the pulmonary infection group was mostly of the phylum Firmicutes and Actinomycetes,with the relative abundance of Roseburia significantly higher(0.8%)than in the other two groups,and the patients with mucositis and diarrhoea were mostly of the phylum Bacteroidetes,enriched with Bacteroides(41.1%).By Lefse analysis of biomarkers,patients with combined mucositis and diarrhoea showed a predominance of subordinate groups of the phylum Proteobacteria,with the bloodstream infection group showing a predominance of the order Pseudomonadales(in the Gammaproteobacteria),the family Aerobacteriaceae and Lactobacillus,and the pulmonary infection group showing a predominance of the order Aeromonadales.6.The development of infections and complications at different sites is associated with differential metabolic pathways of the intestine.Differential pathways in patients with mucositis and diarrhea were associated with kinase and phosphatase pathways and enhanced fibrin and cell membrane structural disruption.Patients with bloodstream infections had enhanced aerobic respiration I cytochrome C pathway and diminished tryptophan biosynthesis and polymyxin resistance during chemotherapy.Patients in the pulmonary infection group showed statistically significant differences in the degradation of limonene and pinene,enhanced metabolic pathways for L-threonine degradation,and enhanced threonine aminolytic enzyme activity.Conclusions:1.AML patients presenting with bloodstream infections have clinical risk factors,such as neutrophil count<0.5 ×109/L,and the main infectious agents are Klebsiella pneumoniae,Enterobacter and Pseudomonas aeruginosa.Blood macrogenome sequencing compensates to some extent for the lack of blood cultures.2.The Shannon index and composition of the gut microbiota of AML patients prior to treatment are somewhat predictive of clinical infections,including the occurrence of bloodstream infections.3.AML patients undergo dynamic changes in the structure of the gut microbiota during chemotherapy,with the infected groups all showing an increase in Proteobacteria and a decrease in Firmicutes and Bacteroidetes at the phylum level,and a decrease in beneficial bacteria and an increase in conditionally pathogenic bacteria at the genus level.4.The metabolic pathways of the gut microbiota differed between the infected and non-infected groups,especially in relation to the occurrence of bloodstream infections and mucositis,and the composition and structure of the gut microbiota differed in AML patients with different types of infections.Patients with bloodstream and pulmonary infections showed a predominance of y-proteobacteria,while patients with mucositis and diarrhoea showed a predominance of the subordinate flora of Proteobacteria and Bacteroides.