In human plasma, cell-free bacterial DNAs offer fingerprints for immune-related illnesses.

Microbiota is becoming more widely acknowledged as a critical component of human health. A wide spectrum of human illnesses has been linked to changes in bacterial community structure. Most microbiota-targeting therapies, such as probiotics, prebiotics, and faecal transplants, try to change the bacterial community's composition. We show that cell free bacterial DNAs (cfbDNAs) are widely found in human bloodstreams and that they emerge progressively with growth. Furthermore, utilizing real-time PCR measurement and high-throughput 16S rDNA sequence studies, patients with immune-related disorders, such as Inflammatory Bowel Disease (IBD), Kawasaki Disease (KD), and HIV, had larger levels of cfbDNAs with lesser microbial biodiversity than healthy individuals. Further analyses indicate that 173 genera are more abundant in healthy people than in patients, resulting in "molecular phenotypes" of the respective disorders in the microbiome, particularly in IBD patients post/pre-therapy. Although the origins and functions of these cfbDNAs in human circulating bloodstreams are unknown, their taxonomic variances give fingerprints for future noninvasive and safe pre-diagnosis or prognosis applications, as well as hints for a better understanding of host-microbiota interactions.