See below. All things are relative. Ancef (cefazolin) is relatively safe although the risk of getting c. Difficile again is real. The risk of surgical wound infection needs to be weighed against the risk of getting c. Difficile again. If you take the ancef (cefazolin) and develop diarrhea get stool checked for c. Difficile again.
Maybe. If you have a history of c. Difficile, or have a lot of medical conditions which are inflammatory, you have a higher risk of developing c. Difificile. However a one time dose in a realitively healthy pt. As prophylactic prior to surgery has an extremely low risk for devopling c. Difficile as long as the surgery has no complications. Long term antibc's used after surgery put you at a higher risk.