After how many days of taking antibiotics can you be sure that you were not c diff colonized and hence no c diff infection? from what i understand is you get cdi after taking antibiotics only when colonized and no cdi if not colonized even after abs?

Take some probiotics: Antibiotics do not cause colonization by anything but they do kill off susceptible germs normally in the gut. C.diff is not usually affected by routine antibiotics so if it is there by chance (you ate it) it can overgrow & set stage for problems. The problems usually start when multiple abx are used in sequence or at the same time. C. diff can occasionally be in the gut & produce no problems.