Airway Microbiota In Patients With Stable Asthma With Different Inflammatory Phenotypes

Background and PurposeAsthma is one of the most common chronic airway inflammatory diseases,characterized by a series of respiratory symptoms,such as wheezing,shortness of breath,chest tightness,coughing and reversible airflow limited.It is a heterogeneous disease with different phenotypes.According to the percentage of inflammatory cells in sputum,it can be divided into different inflammatory phenotypes.Different phenotypes mean different underlying disease processes and mechanisms,and the study of these phenotypes can provide theoretical basis for targeted and individualized treatment.In recent years,with the development of next-generation sequencing(NGS),the role of airway microbiome in the occurrence,development and treatment response of asthma has been gradually recognized.However,there are still relatively few studies on airway mycobiome of asthma patients.In this study,we collected induced sputum of asthma patients from the Department of Respiratory and Critical Care Medicine of Nanfang hospital,Southern Medical University.We analyzed the relationship between airway inflammation phenotypes and airway microbiota,the interaction between airway bacteria and fungi community in order to investigate the characteristics of airway microbiota in different inflammatory phenotypes and provide new thinking for future clinical practice.Subjects and MethodsWe recruited asthma outpatients in Department of Respiratory and Critical Care Medicine of Nanfang hospital,Southern Medical University from June 2015 to December 2016,collected their induced sputum and complete electronic medical records and finally a total of 96 cases of asthma patients conformed to the inclusion criteria.The obtained induced sputum samples were divided into two parts,one for the classification of inflammatory cells in sputum and the other for the sequencing of sputum microbiota.According to the percentage of eosinophils and neutrophils in induced sputum,patients were divided into four subgroups,namely eosinophilic asthma(n=13),neutrophilic asthma(n=43),paucigranulocytic asthma(n=22)and mixed granulocytic asthma(n=18).The sputum was sequenced with 16s RNA and ITS 1 genes,and the characteristics of the microbiome and mycobiome of induced sputum were described,analyzed and compared among four subgroups,as well as the interaction of the airway microbiota in asthma patients.Results(1)No significant difference of alpha or beta diversity in sputum bacterial community among four different inflammatory phenotypes.Significant difference was found of alpha diversity in fungal community among the four subgroups(P=0.018),of which was significantly higher in paucigranulocytic group than that in eosinophilic and mixed granulocytic group(P<0.05).The beta diversity of fungal communities in eosinophilic and mixed granulocytic group was significantly different from that in the other two groups(R2=0.016,P<0.05).The percentage of eosinophil in sputum was negatively correlated with the alpha diversity of fungal community.(2)Among 96 asthma patients,three major bacterial genera(with an average relative abundance over 1%)were found in the sputum:Prevotella,Streptococcus and Neisseria.In addition,Prevotella,Streptococcu,Porphyromonas and Fusobacterium were 100%detected in all asthmatic subjects.There were four major fungal genera:Meyerozyma,Schizophyllum,Aspergillus and Candida.(3)The relative abundance of Actinobacillus,Bacillus,Meyerozyma and Phialemoniopsis was significantly different among four inflammatory phenotypes.The percentage of eosinophils in sputum was positively correlated with the relative abundance of Bacillus and Meyerozyma(r=0.296,P=0.005 and r=0.218,P=0.037 respectively),and was negatively correlated with Actinobacillus(r=-0.205,P=0.029).The percentage of neutrophils in sputum was negatively correlated with the relative abundance of Phialemoniopsis(r=-0.194,P=0.036).(4)Proteobacteria in the airway of asthma patients were negatively correlated with Firmicutes,Bacteroidetes and Actinomycetes while positively correlated with Ascomycota and Basidiomycota.At the genus level,Moraxella was negatively correlated with Meyerozyma and Candida.Aspergillus and Schizophyllum were positively correlated,but negatively correlated with Leptotrichia and Streptococcus.ConclusionWe found significant difference of basic genus in airway among different inflammatory phenotype of stable asthma.The relative abundance of Actinobacillus,Bacillus,Meyerozyma and Phialemoniopsis were significantly different among four subgroups.Eosinophils played an important role in the composition of airway fungal community.Moraxella was positively correlated with Meyerozyma,and negatively correlated with Leptotrichia and Prevotella.Aspergillus was positively correlated with Schizophyllum.Airway microbiota may make a difference to the progress of asthma by synergism between pathogenic microorganisms and inhibition of non-pathogenic microorganisms.