Systemic antifungals aren't effective treating the gut because they are absorbed in the upper intestinal tract. They are excreted metabolized by the liver ( the azoles ) with no effectiveness in the intestines. Only the mutated yeast cells that infects the epithelium are targeted by systemic drugs. There isn't blood irrigation in the intestinal lumen and no way to delivery a systemic drug to it. To treat the gut you need a systemic and a non-systemic antifungal. The non systemic will target the colonies living on the lumen and the systemic will target those yeast mutated cells that infect the epithelium.