Clinical factors associated with composition of lung microbiota and important taxa predicting clinical prognosis in patients with severe community-acquired pneumonia

Few studies have described the key features and prognostic roles of lung microbiota in patients with severe community-acquired pneumonia(SCAP).We prospectively enrolled consecutive SCAP patients admitted to ICU.Bronchoscopy was performed at bedside within 48 h of ICU admission,and 16S rRNA gene sequencing was applied to the collected bronchoalveolar lavage fluid.The primary outcome was clinical improvements defined as a decrease of 2 categories and above on a 7-category ordinal scale within 14 days following bronchoscopy.Sixty-seven patients were included.Multivariable permutational multivariate analysis of variance found that positive bacteria lab test results had the strongest independent association with lung microbiota(R2=0.033;P=0.018),followed by acute kidney injury(AKI;R2=0.032;P=0.011)and plasma MIP-1βlevel(R2=0.027;P=0.044).Random forest identified that the families Prevotellaceae,Moraxellaceae,and Staphylococcaceae were the biomarkers related to the positive bacteria lab test results.Multivariable Cox regression showed that the increase inα-diversity and the abundance of the families Prevotellaceae and Actinomycetaceae were associated with clinical improvements.The positive bacteria lab test results,AKI,and plasma MIP-1βlevel were associated with patients’lung microbiota composition on ICU admission.The families Prevotellaceae and Actinomycetaceae on admission predicted clinical improvements.