Multi-Method Characterisation of the Human Circulating Microbiome

Abstract

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Molecular Characterization of Circulating Microbiome Signatures in Rheumatoid Arthritis

“…Such breaches in resistance enable specific microbiota members to overpopulate their usual place of habitation or to colonize areas of the body that they are usually unable to do so (Pflughoeft and Versalovic, 2012). Recent studies have further revealed that evidence of the microbiome (generally at the nucleic acid level) is detectable in the circulatory system and report that this is the result of microorganisms (or parts thereof) moving from their usual place of habitation such as the gut, oral cavity, respiratory tract, into the blood; a process termed atopobiosis (Potgieter et al, 2015;Whittle et al, 2018;Castillo et al, 2019).…”

“…It is almost universally accepted that the circulatory system of healthy humans is sterile based upon our general inability to detect proliferating microorganisms (Potgieter et al, 2015). However, a number of studies report the presence of proliferating organisms in the circulation of apparently healthy subjects (Damgaard et al, 2015;Castillo et al, 2019;Whittle et al, 2019) or the presence of microorganism-associated components such as microbial nucleic acids (DNA and RNA) (Nikkari et al, 2001;Gosiewski et al, 2017;Whittle et al, 2019). Further, culturepositive bacteremia following tooth brushing and the use of oral irrigation devices is well-appreciated (Berger et al, 1974;Maharaj et al, 2012), suggesting that the transient presence of organisms within the circulation is well-tolerated in the healthy host.…”

Multi-Method Molecular Characterisation of Human Dust-Mite-associated Allergic Asthma

“…Additionally, our results were reflective of a previous study investigating the oral microbiome, whereby Firmicutes, Stenotrophomonas , and Lactobacillus were found to be increased in asthmatic subjects compared to the control subjects (95). This suggests that bacterial nucleic acid detected in the blood may have originated from the oral cavities, a theory that we consider in (38).…”

“…Our previous characterisation (38) of the bacterial RNA present in the plasma samples found that the majority of bacterial RNA belonged to the Proteobacteria phylum (Total relative abundance = 83.9%; Control mean = 90.0%; Asthma mean = 80.3%), the Actinobacteria phylum (Total relative abundance = 7.5%, Control mean = 6.0%, Asthma mean = 7.5%), and the Firmicutes phylum (Total relative abundance = 6.6%, Control mean = 3.0%, Asthma mean = 9.0%) ( Figure 6 ).…”

“…We have previously reported evidence of a circulating microbiome in the blood of both asthmatic and healthy patients (38) using oligonucleotide primers reported in (Supplementary Materials, S1). Here, we re-analysed this data with the aim of identifying organisms that were differentially present or abundant dependent on disease status.…”