Anaerostipes hadrus comb. nov., a dominant species within the human colonic microbiota; reclassification of Eubacterium hadrum Moore et al. 1976

Recent molecular analyses suggest that bacteria related to strains SS2/1 and SSC/2, previously reported to be distantly related to Anaerostipes caccae NCIMB 13811T, represent one of the ten most abundant phylotypes detected in adult human faecal samples. These two strains were isolated as d-lactate-utilizing bacteria from faecal samples of a healthy individual. We show here that they share >99.9% similarity in 16S rRNA gene sequence with a new butyrate-producing isolate recovered from a colonic biopsy of a Crohn's disease patient, and also with the sequence reported recently for Eubacterium hadrum ATCC 29173T. Biochemical profiling using API Rapid ID 32A and API ZYM test systems confirmed a close phenotypic similarity to E. hadrum ATCC 29173T, but also indicated that the description of this species should be expanded to include the ability to produce butyrate from d-lactate and acetate. Phylogenetic analysis confirmed an affinity between E. hadrum and members of the genus Anaerostipes (92.3–94.2% sequence similarity) belonging to the family Lachnospiraceae (formerly Clostridium cluster XIVa). Based on phylogenetic, phenotypic and chemotaxonomic evidence it is proposed that E. hadrum be transferred to the genus Anaerostipes with the name Anaerostipes hadrus comb. nov. The type strain of A. hadrus comb. nov. is =ATCC 29173T (=DSM 3319T = VP 82-52T).

► We describe a group of human gut isolates as a new species in the genus Anaerostipes.
► The type strain of Eubacterium hadrum, ATCC 29173T, is closely related to our isolates.
► We propose the renaming of E. hadrum to Anaerostipes hadrus.
► A. hadrus is an important, butyrate-producing bacterial species resident in the human colon.