Heres a quick little movie showing off the bots understanding of items, and being intelligent enough to know when to grab them.
Note that the bot must be able to see the item dropped, it doesn't just "know" an item is there - just like a human.
Also notice that if the bots health is over 100, it understands it doesn't need a pack anymore, but if I wound it, it WILL grab one if it sees one.
This works exactly the same for ammo packs too.