Clostridium Difficile Agar Base, when used with supplements, is a selective medium for the isolation of Clostridium difficile from food and fecal specimens. Clostridium difficile was first isolated from meconium and infant feces in 1935 by Hall and OToole, who proposed the name difficile because it was very difficult to isolate. Keighley associated Clostridium difficile with colitis and diarrhea after antibiotic therapy following gastrointestinal operations. In 1979, George et al developed a medium called CCFA (cycloserine-cefoxitin-fructose agar), which is a bloodless medium, based on the egg yolk agar of McClung and Toabe with fructose as a glucose replacement. The combination of Clostridium Difficile Agar with the supplement is based on this medium. The selective agents D-cycloserine, and cefoxitin inhibit the growth of most Enterobacteriaceae, as well as Enterococcus faecalis, staphylococci, Gram negative, non-sporing anaerobic bacilli, and Clostridia species (except Clostridium difficile), which may be found in large quantities in fecal samples. Peptone proteose provides nitrogen, vitamins, minerals and amino acids essential for growth. Fructose is the fermentable carbohydrate used to enhance recovery and growth of C. difficile. Potassium dihydrogen phosphate and disodium hydrogen phosphate act as a buffer system. Magnesium sulfate is an ion required in a large variation of enzymatic reactions, including DNA replication. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Horse blood provides essential growth factors. Bacteriological agar is the solidifying agent.
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