At first, researchers discovered that on average the CA patients had more gram-negative bacteria and the controls had more gram-positive bacteria. They also found that the relative abundance of three gut bacterial species differentiated CA patients from controls no matter the person’s geographic location, sex or genetic predisposition to the disease.
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CA patients' gut bacteria also appeared to produce more lipopolysaccharide (LPS) molecules, which are those that are one of the main parts of gram-negative bacteria. In mice, LPS molecules have been shown to push CA development, according to a 2017 NIH-funded pre-clinical study.
"Our study demonstrates that CA patients have distinctive microbiome compared to healthy individuals. Analyses at the biosynthesis and gene level indicate that LPS synthesis-related genes are more abundant in CA patients, consistent with a role of gut-generated LPS driving CA disease," the authors wrote.
“This study further shows that CA patients with distinct disease characteristics have different microbiota, and that the combination of plasma biomarker and stool microbiome composition enhances this differentiation.”
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The authors said the study offers the first showing in humans of a “permissive microbiome” linked to the development of neurovascular lesions in the brain.
Some gut bacteria compositions could identify aggressive versus non-aggressive forms of the disease and those with recent symptomatic hemorrhages, further analysis showed. For the first time, they also showed how mixing gut bacteria data with results from blood plasma tests might help doctors make improved diagnoses of how severe a brain disorder may be. The results back an increasing group of evidence for the role gut bacteria play in brain health.