The Genus Alistipes: Gut Bacteria With Emerging Implications to Inflammation, Cancer, and Mental Health

Abstract

<i>Alistipes</i> is a relatively new genus of bacteria isolated primarily from medical clinical samples, although at a low rate compared to other genus members of the <i>Bacteroidetes</i> phylum, which are highly relevant in dysbiosis and disease. According to the taxonomy database at The National Center for Biotechnology Information, the genus consists of 13 species: <i>Alistipes finegoldii, Alistipes putredinis, Alistipes onderdonkii, Alistipes shahii, Alistipes indistinctus, Alistipes senegalensis, Alistipes timonensis, Alistipes obesi, Alistipes ihumii, Alistipes inops, Alistipes megaguti, Alistipes provencensis</i>, and <i>Alistipes massiliensis. Alistipes communis</i> and <i>A. dispar</i>, and the subspecies <i>A. Onderdonkii</i> subspecies vulgaris (vs. <i>onderdonkii</i> subsp.) are the newest strains featured outside that list. Although typically isolated from the human gut microbiome various species of this genus have been isolated from patients suffering from appendicitis, and abdominal and rectal abscess. It is possible that as <i>Alistipes</i> spp. emerge, their identification in clinical samples may be underrepresented as novel MS-TOF methods may not be fully capable to discriminate distinct species as separate since it will require the upgrading of MS-TOF identification databases. In terms of pathogenicity, there is contrasting evidence indicating that <i>Alistipes</i> may have protective effects against some diseases, including liver fibrosis, colitis, cancer immunotherapy, and cardiovascular disease. In contrast, other studies indicate <i>Alistipes</i> is pathogenic in colorectal cancer and is associated with mental signs of depression. Gut dysbiosis seems to play a role in determining the compositional abundance of <i>Alistipes</i> in the feces (<i>e.g</i>., in non-alcoholic steatohepatitis, hepatic encephalopathy, and liver fibrosis). Since <i>Alistipes</i> is a relatively recent sub-branch genus of the <i>Bacteroidetes</i> phylum, and since <i>Bacteroidetes</i> are commonly associated with chronic intestinal inflammation, this narrative review illustrates emerging immunological and mechanistic implications by which <i>Alistipes</i> spp. correlate with human health.