After no more than a week, start to introduce probiotics regularly so you can get your beneficial organisms back to where they should be. FOS, HSOs, and acidophilus are what you'll want to look for. Live, multi-strain acidophilus is what you'll want. The HSOs are kind of pricey, but they do a great job, as does the FOS. Either HSOs or FOS should be started first (you don't need both), as they will set up a good foundation for the acidophilus to really thrive and reproduce, which will in turn get rid of the harmful organisms quicker.