The presence of circulating microbiome in blood has been reported in both physiological and pathological conditions, although its origins, identities and function remain to be elucidated. This... Show moreThe presence of circulating microbiome in blood has been reported in both physiological and pathological conditions, although its origins, identities and function remain to be elucidated. This study aimed to investigate the presence of blood microbiome by quantitative real-time PCRs targeting the 16S rRNA gene. To our knowledge, this is the first study in which the circulating microbiome has been analyzed in such a large sample of individuals since the study was carried out on 1285 Randomly recruited Age-Stratified Individuals from the General population (RASIG). The samples came from several different European countries recruited within the EU Project MARK-AGE in which a series of clinical biochemical parameters were determined. The results obtained reveal an association between microbial DNA copy number and geographic origin. By contrast, no gender and age-related difference emerged, thus demonstrating the role of the environment in influencing the above levels independent of age and gender at least until the age of 75. In addition, a significant positive association was found with Free Fatty Acids (FFA) levels, leukocyte count, insulin, and glucose levels. Since these factors play an essential role in both health and disease conditions, their association with the extent of the blood microbiome leads us to consider the blood microbiome as a potential biomarker of human health. Show less
The human body is colonized by microorganisms, collectively referred to as the human microbiota. Microbiota disturbance has been associated with a wide range of diseases and is the focus of many... Show moreThe human body is colonized by microorganisms, collectively referred to as the human microbiota. Microbiota disturbance has been associated with a wide range of diseases and is the focus of many research initiatives. The most widely used approach is based on sequencing of the 16S rRNA gene. This method can also be very valuable for clinical microbiology as it enables identification of a theoretically unlimited number of bacteria present in a specimen and permits (semi)quantitative information about the composition of a microbial community. In this thesis we investigated whether 16S rRNA gene profiling would have added value for direct diagnostics and/or as an indirect tool for evaluating cheaper diagnostic tests or evaluating treatments. The studies in this thesis were focused on respiratory tract infections, bacterial vaginosis, atopic dermatitis or male genital lichen sclerosus. The main challenge of 16S rRNA gene profiling is the clinical interpretation of relative abundance of the identified bacteria in clinical specimens. More clinical studies with appropriate control groups are needed to define and validate clinically relevant cut-off values, to measure microbiota variability over time and to determine microbial phenotypes. The clinical value of 16S rRNA gene profiling will probably become clear in the forthcoming years. Show less
