Microbiome in Blood Samples From the General Population Recruited in the MARK-AGE Project: A Pilot Study

Abstract

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 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.

Human Blood Bacteriome: Eubiotic and Dysbiotic States in Health and Diseases

“…Proteobacteria, Enterobacteriaceae in particular, were raised in cirrhosis with compensated liver function; nonetheless, a lower proportion of Enterobacteriaceae was observed in HBV patients with acute decompensated liver function [17,63]. Interestingly, an increase in Enterobacteriaceae in a subgroup of patients with HBV and acute decompensated liver function resulted in a higher mortality rate than in the other groups [63].…”

“…Cirrhosis with compensated liver function might result in changes in the blood bacteriome towards an increase in Proteobacteria and a decrease in Firmicutes [34]. Decompensated liver function compared with normal liver function might lead to blood dysbiosis, as shown by a decline in Actinobacteria and Deinococcus-Thermus [63]. Additionally, a stepwise increase was shown in the concentration of the 16s rRNA bacterial gene from normal liver function to hepatitis B virus infection (HBV) with compensated liver function to HBV with decompensated liver function [63].…”

“…Decompensated liver function compared with normal liver function might lead to blood dysbiosis, as shown by a decline in Actinobacteria and Deinococcus-Thermus [63]. Additionally, a stepwise increase was shown in the concentration of the 16s rRNA bacterial gene from normal liver function to hepatitis B virus infection (HBV) with compensated liver function to HBV with decompensated liver function [63]. Proteobacteria, Enterobacteriaceae in particular, were raised in cirrhosis with compensated liver function; nonetheless, a lower proportion of Enterobacteriaceae was observed in HBV patients with acute decompensated liver function [17,63].…”

“…Additionally, a stepwise increase was shown in the concentration of the 16s rRNA bacterial gene from normal liver function to hepatitis B virus infection (HBV) with compensated liver function to HBV with decompensated liver function [63]. Proteobacteria, Enterobacteriaceae in particular, were raised in cirrhosis with compensated liver function; nonetheless, a lower proportion of Enterobacteriaceae was observed in HBV patients with acute decompensated liver function [17,63]. Interestingly, an increase in Enterobacteriaceae in a subgroup of patients with HBV and acute decompensated liver function resulted in a higher mortality rate than in the other groups [63].…”

How Advanced Is Our Understanding of the Role of Intestinal Barrier Dysfunction in the Pathogenesis of Recurrent Urinary Tract Infections

“…Most of the patients with bacterial translocation to mesenteric lymph nodes (the most reliable method of bacterial translocation evaluating in humans) showed no clinical infectious complications ( Vaishnavi, 2013 ; Mohammad and Thiemermann, 2021 ). Besides, similar to the urinary microbiome, recent advances in culture-independent methods rejected the dogma of blood “sterility” and the existence of a “healthy” human blood microbiome has been demonstrated ( D’Aquila et al, 2021 ; Castillo et al, 2019 ; Shah N. B et al, 2019 ). Unlike the clinical relevance of gut dysbiosis to human health, the problem of blood microbiome dysbiosis has only been addressed in a limited number of studies.…”