Varying intestinal permeability has usually been related to inert compounds. More recently there has been some study on the significance of certain microbe metabolites, but the evidence for any kind of large scale microbial translocation in people that are not very sick (ie septic) is extremely tenuous.
"Key controversies in blood microbiome research are the susceptibility of low-biomass samples to exogenous contamination and undetermined microbial viability from NGS-based microbial profiling"
Just because you can amplify some sporadic bacteria DNA from the blood does not mean that bacteria are hanging out in the blood in a physiologically meaningful way.
A lot of it is frankly junk science in disreputable journals.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10059777/
"Key controversies in blood microbiome research are the susceptibility of low-biomass samples to exogenous contamination and undetermined microbial viability from NGS-based microbial profiling"
Just because you can amplify some sporadic bacteria DNA from the blood does not mean that bacteria are hanging out in the blood in a physiologically meaningful way.
A lot of it is frankly junk science in disreputable journals.
On the otherhand: https://www.nature.com/articles/s41564-023-01350-w
"Despite this, we found no evidence for microbial co-occurrence relationships, core species or associations with host phenotypes."