83 Yr Old With Dementia Male Recovering From Aspiration Pneumonia

83 yr old with dementia male recovering from aspiration pneumonia and has a peg tube for feeding. Has c-diff and on vancomycin. Is in post acute rehab right now. How will we know when he is free of it? I am told when he stops diarrhea for 3 days. Does not seem right to me? What tests should one have?
Also doctors say no conclusive info for taking probiotics. What do you think?

Thank you very much