[organisms] see Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
   Domain Bacteria Woese et al. 1990
     Phylum Firmicutes corrig. Gibbons and Murray 1978 (Approved Lists 1980)
       Class "Clostridia" Garrity et al. 2001 nom. ined. see Class Clostridia Rainey 2010
         Order Clostridiales Prévot 1953 (Approved Lists 1980)
           Family Clostridiaceae Pribram 1933 (Approved Lists 1980)
             Genus Clostridium Prazmowski 1880 (Approved Lists 1980)
               Clostridium difficile (Hall and O'Toole 1935) Prévot 1938 (Approved Lists 1980)