Investigation of bacterial remnants in blood and their implications in asthma

This study aimed to investigate the distribution of bacterial DNA among different blood components and its relationship with asthma. Blood components including plasma, buffy coat, and red blood cells were initially separated to determine the distribution of bacterial DNA between blood compartments. The study included 131 participants divided into normal-weight control (n=30), obese control (n=30), normal-weight asthma (n=15), and obese asthma (n=44) groups. Bacterial DNA levels were measured using quantitative PCR, and detailed microbiome profile analyses were performed on selected samples using 16S rRNA and shotgun metagenomic sequencing. Analysis of blood components revealed that the majority of bacterial DNA (89.77%) was localized in the buffy coat, with higher concentrations in PMNs (70.64%) compared to PBMCs (29.36%). Red blood cells contained 10.20% of total bacterial DNA, while only 0.03% was detected in plasma. Metagenomic analyses showed that obese individuals had higher proportions of gut-derived bacteria such as Escherichia/Shigella and skin-derived bacteria like Cutibacterium acnes in their bloodstream compared to normal-weight individuals. These findings suggest that compromised gut and skin barrier integrity in obesity may lead to bacterial translocation. Positive correlations were observed between circulating bacterial DNA levels and inflammatory markers. This study demonstrates that bacterial DNA in the bloodstream may serve as a potential indicator of systemic inflammation and epithelial barrier dysfunction, potentially contributing to obesity-associated chronic inflammation. Our findings highlight that circulating bacterial DNA could be used as a biomarker and emphasize the importance of developing therapeutic approaches targeting epithelial barrier function.