Go for prevention - Acidophilus tablets
I can recommend taking Acidophilus tablets available from any good health shop/herbal remedy store. They contain the "good bacteria" which helps regulate the digestive system. This is more helping mother nature than chemical warfare with antibiotics.
I think they sell 2 types - check they dont have to be stored in the fridge if you are going to stay somewhere without a fridge available. The other type can be stored at room temperature.
Worked for me when on my first trip to India a few years back.
I would also agree on keeping to bottled water, no ice etc. advice too.