Reclassification of Clostridium difficile as Clostridioides difficile (Hall and O'Toole 1935) Prévot 1938

Area of Science:

• Microbiology
• Bacteriology
• Taxonomy

Background:

• The genus Clostridium is undergoing reclassification, impacting the taxonomy of related bacteria.
• Clostridioides difficile is a significant cause of hospital-acquired infections and mortality.
• Phylogenetic analysis reveals Clostridioides difficile is distant from Clostridium sensu stricto.

Purpose of the Study:

• To propose a new genus, Clostridioides gen. nov., for Clostridium difficile and related species.
• To reclassify Clostridium difficile and Clostridium mangenotii into the novel genus.
• To address the taxonomic ambiguity arising from the proposed restriction of the genus Clostridium.

Main Methods:

• 16S rRNA gene sequence analysis for phylogenetic comparison.
• Phenotypic characterization including gas and fatty acid production.
• Chemotaxonomic analysis of cell wall peptidoglycan (meso-DAP).

Main Results:

• Clostridium difficile and Clostridium mangenotii share 94.7% 16S rRNA gene sequence similarity.
• Both species produce abundant H2 gas and specific fatty acid profiles (C16:0 major).
• Meso-diaminopimelic acid (meso-DAP) is the diagnostic diamino acid in their peptidoglycan.

Conclusions:

• A new genus, Clostridioides gen. nov., is proposed to accommodate Clostridium difficile (type species) and Clostridium mangenotii.
• Clostridioides difficile comb. nov. and Clostridioides mangenotii comb. nov. reflect their distinct phylogenetic and phenotypic characteristics.
• This reclassification clarifies the taxonomy of medically important clostridial species.