March 02, 2019
3 min read

Clostridioides difficile: What's in a name?

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Ellie Goldsteing, MD
Ellie J.C. Goldstein
L. Clifford McDonald, MD 
L. Clifford McDonald

The CDC has begun using Clostridioides difficile instead of Clostridium difficile to refer to the bacterium that commonly causes infectious diarrhea, raising questions about the importance of naming conventions for well-known organisms.

The change followed a decision early last year by the Clinical and Laboratory Standards Institute (CLSI) to begin calling it Clostridioides difficile, after experts resisted changing it to another name: Peptoclostridium difficile.

An article published on the American Society for Microbiology (ASM) website characterized the name change as a long time coming.

“With improved genetic testing and routine 16S rRNA and ribosomal protein sequencing, it was recognized that the taxonomic classification of C. difficile should be changed,” Monica Mahoney, PharmD, BCPS-AQID, clinical pharmacy coordinator at Beth Israel Deaconess Medical Center in Boston, told Infectious Disease News. “Originally, ‘Peptoclostridium’ was proposed. However, there was global backlash because of loss of the terms ‘C. diff’’ and ‘CDAD’ (Clostridium difficile-associated diarrhea).”

According to the ASM article, a change to P. difficile would not only have negatively affected patient care, it would have cost the health care industry a lot of money and time to implement the change.

Ellie J.C. Goldstein, MD, Infectious Disease News Editorial Board member, clinical professor of medicine at the University of California, Los Angeles School of Medicine, and director of the R.M. Alden Research Laboratory in Santa Monica, California, noted that C. difficile is technically in a different clade and is not a clostridium.

“The genus Clostridium was a waste basket for gram-positive spore-forming anaerobic rods,” Goldstein told Infectious Disease News. “They weren’t necessarily all related, but they were related by gram stain, some biochemical tests and visually.”

He explained that Clostridioides difficile means Clostridia-like, and that the reclassification to Clostridioides sidesteps any confusion that “would result from re-naming it entirely.”

“Fortunately, with the change from ‘Clostridium’ to ‘Clostridioides,’ the abbreviations ‘C. diff,’ ‘CDAD,’ and others remain applicable,” Mahoney said.

L. Clifford McDonald, MD, associate director for science in the CDC’s Division of Healthcare Quality Promotion, told Infectious Disease News that the CDC’s decision to transition to a new name was based on scientific evidence and the CLSI decision.

“Given that clinical microbiology laboratories might be more likely to transition to the new name following the change by CLSI — with Clostridioides difficile more likely to appear in clinical lab reports — we felt it time to make the transition on our website and all our publications,” McDonald explained.

Herbert L. Dupont, MD
Herbert L. Dupont

However, guidelines for C. difficile on the Infectious Diseases Society of America’s website still reference Clostridium rather than Clostridioides.

IDSA told Infectious Disease News that the name change has been implemented within the organization and that all subsequent articles and guidelines will reflect that. However, there is no plan to revise previous guidelines. Additionally, the Society for Healthcare Epidemiology of America told Infectious Disease News that experts within the organization have decided to change the name as well to align with the CDC.

Herbert L. Dupont, MD, Infectious Disease News Editorial Board member and professor of epidemiology and infectious diseases at the University of Texas Health Science Center at Houston, explained that many in the field find the categorization of organisms to be “complex and confusing.”

For clinicians and patients, the organism will continue to be referred to as ‘C. diff,’” Dupont told Infectious Disease News. “The important change will occur with publications where journals will expect to be current with organism identification.” – by Marley Ghizzone


ASM. Celebrating successes and contemplating messes in bacterial taxonomy. Accessed February 27, 2019.

CDC. Clostridioides difficile infection. Accessed February 27, 2019.

Oren A, Garrity GM. Int J Syst Evol Microbiol. 2017;doi:10.1099/ijsem.0.001149.

Disclosures: Dupont reports receiving grants from Rebiotix and being a consultant to Aries and Salix/Valeant. Goldstein and Mahoney report numerous ties to industry. McDonald reports no relevant financial disclosures