I had a couple courses of IV antibiotics to fight a severe tooth infection. All the oral surgeons who came in to check on me recommended picking up a few bottles of probiotic drinks on my way home.
And some cheddar cheese. https://en.wikipedia.org/wiki/Lacticaseibacillus_casei is theorized to be a sort of a halo probiotic - it doesn't do the work, but it makes you GI tract more hospitable to the bacteria that do.
There are cheddar cheeses though that barely rank the name. Quality over quantity here. Buy the small block of fancy cheddar, not whatever name the food megacorporations are using locally.