P02 – Innate Lung Microbiota of Mice Undergo Morbid Transformation in Response to Acute Lung Injury
Author(s):
Background: Acute lung injury (ALI) and severe acute respiratory distress syndrome (ARDS) are among the risk factors associated with elective surgery. Understanding of interaction between lung injury and innate lung microbiota opens new modalities of treatment for ALI, ARDS and acute lung inflammation.
Hypothesis: We hypothesize that ALI affects lung microbiota causing morbid transformation.
Methods: The C57BL/6J mice (8-10 wk old, Jackson Laboratories) were divided in groups: “ALI” (n=6) which received LPS (Escherichia coli O55:B5) via intratracheal injection; “Control” (n=7) which received sterile water. Bronchoalveolar lavage (BAL) was performed at 72h after treatment. Bacterial DNA was extracted, normalized to 1 ml BAL, and used for QPCR and 16S rRNA gene-tags (V3-V4) sequencing.
Results: QPCR detected 5-fold increase of bacterial load in BAL samples from the ALI mice (p=0.03). The community complexity remained unchanged after LPS treatment (p=0.7), while Shannon diversity index indicated the increase of community evenness in response to ALI (p=0.07). This analysis suggests that the observed bacterial growth is attributed to species existing within the lung ecosystem before the ALI. Principal coordinate analysis indicated that LPS treatment explained 66% of total variation in the dataset. The separation between control and ALI groups was significant (ANOSIM test, p=0.005). The Metastats-based comparison of bacterial abundances between control and ALI groups revealed significant (p<0.05) changes in the abundance of 6 bacterial genera: the genera Tumebacillus, Bradyrhizobium, Jeotgalicoccus, as well as the unclassified lineage from the class Betaproteobacreia lost the abundance in response to ALI; pathobionts Brucella (class Alfaproteobacteria) and Stenotrophomonas (class Gammaproteobacteria) were blooming (6-10 folds increase, p<0.05) in response to ALI.
Conclusions: The microbial community reaction to ALI is attributed to the loss of Firmicutes (genus Tumebacillus) and bloom of Proteobacteria (genera Brucella and Stenotrophomonas). We demonstrated that pathological transformation of lung microbiota is attributed to the set of inborn lung pathogens rather than the external infection. We further hypothesize that ARDS could be prevented via control of the pathobiont-related lung microenvironment.