Editors' ChoiceRespiratory Distress

Microbiome goes to the ICU

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Science Translational Medicine  19 Feb 2020:
Vol. 12, Issue 531, eaba9022
DOI: 10.1126/scitranslmed.aba9022

Abstract

Lung microbiota predicts outcomes in critically ill mechanically ventilated patients.

The study of the microbiome has yielded fascinating insights into the pathogenesis of specific diseases. In the lung, we have moved from considering it sterile to proving that the lung microbiome has a definite role in specific disease conditions. However, the failure to link differences in lung microbiota to clinically meaningful outcomes in a more generalized context has remained a limitation.

To address this problem, Dickson et al. collected bronchoalveolar lavage samples from 91 mechanically ventilated patients within 24 hours of admission to the ICU. Their aim was to predict clinical outcomes for critically ill patients using features of their lung microbiomes. First, the authors validated their method of sample collection using miniature bronchoalveolar lavages for the analyses of bacterial content and diversity. Thereafter, using 16s RNA sequencing, they defined the characteristics of these bacterial communities and compared outcomes, namely (i) ventilator free days and (ii) clinical diagnosis of acute respiratory distress syndrome (ARDS), a condition with multifactorial etiology that portends poor outcomes. They observed that bacterial burden, but not overall diversity, predicted duration of ventilator need and the clinical diagnosis of ARDS even after adjusting for age, gender, severity of illness, and presence of clinical pneumonia. An interesting finding was that gut-associated bacterial families (Lachnospiraceae and Enterobacteriaceae) were prominent in the group of patients with poorer outcomes, suggesting that translocation of gut bacteria may play a role in mediating outcome.

This is the first study to use early lung microbiota from critically ill patients with diverse underlying diagnoses to predict clinical outcomes. Although further mechanistic studies are still needed to elucidate the contributions of remote (lung-gut) versus local (lung-lung) microbiota interactions in shaping these outcomes, the current study serves as an important step in bridging the translational gap in the field.

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