Exploratory Study Of Risk Factors For Stroke-associated Pneumonia Based On Gut Microbiota And Its Metabolites Short-chain Fatty Acids

BackgroundStroke-associated pneumonia(SAP)is the primary complication of stroke,but effective therapy is limited.Identifying potential modified risk factors is warranted.ObjectiveWe aimed to evaluate the association between gut microbiome and its metabolites in acute ischemic stroke(AIS)patients during early stage and the occurrence of SAP,to explore whether dysbiosis of the gut microbiota and its metabolites short-chain fatty acids(SCFAs)during early stage of AIS was potential risk factors for SAP and to provide clinical evidence for this purpose.MethodsFirst,we conducted a prospective observational study and 188 AIS patients were enrolled as the training cohort.Fecal and serum samples were collected at admission.SAP was diagnosed by specialized physicians,and disease severity scores were recorded.Fecal samples were subjected to 16S rRNA V4 tag sequencing and analyzed with QIIME and LEfSe.Associations between the most relevant taxa and SAP were analyzed and validated with an independent cohort.We further assessed the gut metabolites,the fecal SCFAs,and assessed the relationships between these metabolites and SAP and severe pneumonia.Serum D-lactate(D-LA),intestinal fatty acid-binding protein(iFABP)and lipopolysaccharide binding protein(LBP)levels were also measured.ResultsOverall,188 AIS patients were enrolled as the training cohort and 52 patients(27.7%)had SAP.The gut microbiota community at early stage significantly differed between SAP and non-SAP patients;specifically,Roseburia depletion and opportunistic pathogen enrichment were noted in SAP patients,as confirmed in the another AIS cohort(the validation cohort,n=144,28 SAP[19.4%]).Based on multivariate analysis,Roseburia was identified as a protective factor against SAP in both cohorts(training,aOR 0.52;95%CI,0.30-0.90;validation,aOR 0.44;95%CI,0.23-0.85).The combination of these taxa significantly associated with SAP into a microbial dysbiosis index(MDI)revealed that dysbiosis positively related to inflammatory status and poor clinical outcome in AIS patients;and that dysbiosis was an independent risk of SAP as it increased nearly 2 times the risk of SAP(training,aOR 1.95;95%CI,1.19-3.20;validation,aOR 2.22;95%CI,1.15-4.26).The MDI showed moderate-to-high performance in identifying SAP(Area under the ROC curve,AUC,training cohort,0.750;validation cohort,0.800,respectively).Patients with severe pneumonia had higher MDI with lower abundance of gut Roseburia compared to those with mild pneumonia.Secondly,the results of the gut metabolites showed that significantly lower fecal SCFA levels,including acetate,propionate,butyrate and valerate,and higher serum D-LA levels were observed in SAP patients compared to those without SAP.Significantly,patients with severe pneumonia had lower fecal SCFAs,especially butyrate and valerate,compared to those with mild pneumonia.Lower fecal SCFAs were independent risks of SAP and severe pneumonia.Furthermore,SAP was an independent risk factor of 30-day death and 90-day unfavorable outcome.Patients with severe pneumonia had worse clinical outcome.ConclusionWe demonstrated that a microbial community with depleted Roseburia and enriched opportunistic pathogens is associated with increased risk of SAP among AIS patients.The levels of SCFAs were lower in those with SAP,especially those with severe pneumonia.Targeting gut microbiota and its associated metabolites,such as SCFAs,might be useful for improving or even preventing SAP and severe pneumonia,and provides new clues for stroke treatment.