We use Brewer’s yeast in our grain-free Butternut meals as it's one of the best sources of natural B vitamins and is also a complete protein - this is very different from the type of yeast that can cause a yeast infection and one does not cause the other.
Yeast infections in dogs are almost exclusively caused by a type of yeast called Malassezia pachydermatis. This typically causes problems in ears, facial skin folds, armpits and between the toes.
If your dog is suffering with a yeast infection, your vet might have recommended an antifungal shampoo or medicated wipes to help reduce the levels of yeast on the skin - this is great advice. You pooch might have outbreaks every now and again (some breeds can be prone to it), but with shampoos, wipes and a grain-free diet (like Butternut) these infections can easily be kept on top of.