Keep mob NBT data when placed back down after being in an (item)

To further explain, I have a worm that is picked up in a bottle of dirt. The worms can be changed in some ways with NBT data (beyond the point) and I would like to keep that NBT data when placing the worm again. Currently I am summoning a new worm but that obviously won't be the same worm. I am basically trying to make something like the buckets of fish. Is there a better way to do this? Thanks :D