What distinguishing feature is seen in Clostridium difficile colonies on CFFA?

Clostridium difficile colonies on Cystine-Heart Agar with Egg Yolk (CFFA) typically present as yellow ground glass colonies. This visual characteristic is associated with the organism's metabolism and pigmentation. The yellow coloration is due to the production of lecithinase or other metabolic byproducts that cause specific reactions in the media.

On CFFA, C. difficile grows under anaerobic conditions, and the appearance of these colonies aids in their identification in the laboratory. The ground-glass quality signifies growth characteristics that are typical of this anaerobic bacterium. Recognizing such features can assist microbiologists in differentiating C. difficile from other potential pathogens in stool samples or other clinical specimens.

The other choices reflect different characteristics associated with other bacterial species or conditions and do not accurately represent C. difficile on this specific medium.