Blood microbiome: a new marker of gut microbial population in dogs?

The characterization of the microbial population of many niches of the organism, as the gastrointestinal tract, is now possible thanks to the use of high-throughput DNA sequencing technique. Several studies in the companion animals field already investigated faecal microbiome in healthy or sick subjects, although the methodologies used in the different laboratories and the limited number of animals recruited in each experiment does not allow a straight comparison among published results. Previously, our research focused on the characterization of the microbial taxa variability in 340 faecal samples from 132 healthy dogs, collected serially from several in house experiments, in relation to diet and sex. The results supported the responsiveness of microbiota to dietary and sex factors and allowed to cluster dogs with high accuracy. For the present study, intestinal and blood microbiota of healthy dogs from different breeds, genders, ages and food habits have been collected, with three principal aims: firstly, to confirm the results of our previous study regarding the faecal microbiome affected by the different type of diet; secondly, to investigate the existence of a blood microbial population even in heathy subjects; and thirdly, to seek for a possible connection between the faecal and the blood microbiota. Limited researches are published on blood microbiota in humans and this is the first evidence of the presence of a bacterial population in the blood of dogs. Moreover, gut and blood microbiota can discriminate the animals by factors such as diet, suggesting some relationship between them. These preliminary results make us believe in the use of the blood microbiome for diagnostic purposes, such as researching and preventing gut inflammatory diseases.