Well, I don’t know how to answer that one. Your toilet would have to be pretty dirty and pretty grubby for you to get a yeast infection. I personally wouldn’t use toilets that were that unhygienic that I would be concerned. I would probably choose a better toilet or a cleaner toilet or perhaps use one of those paper things you can put on the toilet seat before you sit on the toilet.
So, it’s not really likely that you’re going to get a yeast infection from a dirty toilet. I would question why you would need to use a toilet that dirty for you to be concerned about getting an infection.
I don’t think I’d pay too much attention to this question really. Practice a bit more hygiene and if you do use a dirty toilet, maybe have a shower when you get home and clean up properly.
It is more likely that you’re going to get a yeast infection from a locker room or gym floor or having a shower in those sorts of areas where you can pick up a foot fungal infection, but not likely you’re going to pick up thrush or vaginal or genital yeast infections from a toilet seat. You wouldn’t want to be sitting on a toilet seat that you had any suspect issues about anyway.
I hope that answers your question.