POSTINJURY PNEUMONIA INDUCES A UNIQUE BLOOD MICROBIOME SIGNATURE.

Background : Previous preclinical studies have demonstrated a pathobiome after traumatic injury; however, the impact of postinjury sepsis on gut epithelial permeability and bacterial translocation remains unknown. We hypothesized that polytrauma with postinjury pneumonia would result in impaired gut permeability leading to specific blood microbiome arrays. Methods : Male and proestrus female Sprague-Dawley rats were subjected to either polytrauma (PT), PT plus 2-hours daily chronic restraint stress (PT/CS), PT with postinjury day 1 inoculation with pseudomonas pneumonia (PT + PNA), PT/CS + PNA, or naive controls. Whole blood microbiome was measured serially using high-throughput 16S rRNA sequencing and QIIME2 bioinformatics analyses. Microbial diversity was assessed using Chao1/Shannon indices and principle coordinate analysis. Intestinal permeability was evaluated by plasma occludin and lipopolysaccharide-binding protein assays. Results : PT/CS + PNA had increased intestinal permeability compared to uninfected counterparts (PT/CS) with significantly elevated occludin ( P < 0.01). Bacteria was not detected in the blood of naïve controls, PT or PT/CS, but was present in both PT + PNA and PT/CS + PNA on days 2 and 7. The PT/CS + PNA blood biome showed dominance of Streptococcus compared to PT + PNA at day 2 ( P < 0.05). Females PT/CS + PNA had a significant abundance of Staphylococcus at day 2 and Streptococcus at day 7 in the blood biome compared to male counterparts ( P < 0.05). Conclusion : Multicompartmental trauma with postinjury pneumonia results in increased intestinal permeability and bacteremia with a unique blood biome, with sexual dimorphisms evident in the blood biome composition. These findings suggest that postinjury sepsis has clinical significance and could influence outcomes after severe trauma and critical illness.