Etienne,
Amp B, Nystatin, and Natamicin are Fungicial at tolerable doses. ( the azoles aren't ) So, you can try with oral Amp B that is broader in spectrum than Nystatin. There are two problems with it. One is they aren't absorbed by the intestinal cells when taken in oral form. So how they can kill an intracellular infection when they don't cross the ephitelium ?? Second, these polyenes aren't effective against all candida species. Botton line, to kill the residual fungal overgrowth in the cells you have to go bloodstream way with a fungicidal drug ( IV Echinocandins or Amp B ) or to have an oral fungicidal drug that cross the intestinal lining.
Jorge.