Affirmative BHX_SLF, works well for me - you can even get pressed strawberry flavour tablets, I eat them like sweeties when I'm there. The theory is that bugs such as salmonella aren't destroyed by your stomach acid unlike most bacteria and grow very well on their own in your intestine which is normally "clean", bifidus and lactobacillus also survive stomach acid and provide effective competition, lowering the effect of the bad bugs substantially.
If you do perchance get a bad dose, the best thing to bring to treat it is charcoal, and if you don't have it, ask the locals as they have natural liquid cures of the "just drink it down, don't smell or taste it" variety that work very well and quickly - some great war stories of that variety from mates who were down there 15 years ago.