C. diff

noun

ˈsē-ˈdif 

variants or less commonly C-diff

plural C. diff also C-diff

: a rod-shaped, spore-producing, gram-positive bacterial clostridium (Clostridium difficile) that occurs widely in soil and water and sometimes in human and animal intestines and that may produce a toxin causing intestinal illness (such as diarrhea) especially in those receiving antibiotic therapy

Many healthy people harbor a few C. diff among the millions of bacteria in the colon. When C. diff hangs out in the form of inert spores, it's harmless. But if antibiotic therapy knocks off the normal bacteria, C. diff springs to life, producing two toxins that attack the colon.

—Harvey B. Simon

Examples of C. diff in a Sentence

Recent Examples on the Web

The infection, known as C. diff colitis, tends to occur when patients take antibiotics, which can kill good bacteria in the gut. —Ava Erickson, Outside Online, 29 Apr. 2025

People who are older and have weaker immune systems are also at higher risk of experiencing gut symptoms and more serious problems like C. diff, an overgrowth of a type of bacteria called Clostridioides difficile, which can cause diarrhea, nausea, fever, stomach pain, and colon inflammation. —Beth Krietsch, SELF, 7 Apr. 2025

For example, fecal microbiota transplants have shown to be an effective treatment for C. diff. —Cheri Lucas Rowlands, Longreads, 5 Dec. 2024

Diarrhea can start due to Vibrio cholerae (cholera), Clostridioides difficile (C. diff), or Escherichia coli (E. coli) bacteria. —Mark Gurarie, Health, 2 Nov. 2024

It has also been shown that people who take PPIs may be more likely to get pneumonia and develop an infection with C. diff. —Amber J. Tresca, Verywell Health, 21 Oct. 2024

In addition, antibiotics may harm the healthy balance of bacteria in the gut, leading to a severe type of diarrhea known as Clostridioides difficile (C. diff, sometimes referred to as Clostridium difficile). —Patricia Weiser, Pharmd, Verywell Health, 9 Oct. 2024

Among the bacteria: E. coli, C. diff and the superbug MRSA, which resists common antibiotics and can cause life-threatening infections, according to the clinic. —Nick Halter, Axios, 18 Aug. 2024

Such uses could include viruses for gene therapy and intestinal bacteria to treat a gut infection known as C. diff. —Bill Sullivan, Discover Magazine, 12 Aug. 2024

Word History

First Known Use

1990, in the meaning defined above

Medical Definition

C. diff

noun

ˈsē-ˈdif 

variants also C-diff

plural C. diff also C-diff

: a rod-shaped, spore-producing, gram-positive bacterium (Clostridium difficile) that occurs widely in soil and water and sometimes in human and animal intestines and that may produce a toxin causing intestinal illness (such as diarrhea) especially in those receiving antibiotic therapy

Many healthy people harbor a few C. diff among the millions of bacteria in the colon.

—Harvey B. Simon

Anyone admitted to the hospital with diarrhea and a recent history of using antibiotics or other drugs linked to C. diff infections is isolated immediately and tested for the bacteria.

—Peter Eisler

C-diff, as it's called, is a rising problem across North America and in parts of Europe.

—Ben Harder