Optibac \"For Those On Antibiotics\" is for people who are taking antibiotics (e.g. penicillin, tetracycline, doxycycline), or who have recently finished an antibiotic course. The strains of natural bacteria in this supplement are especially selected for their suitability and safety. These two high quality strains of natural bacteria, Lactobacillus acidophilus Rosell-52 and Lactobacillus rhamnosus Rosell-11, have been extremely well-researched, and are scientifically proven to survive to reach the gut alive, even during a course of antibiotics. More about the strains contained in this probiotic supplement: - __Lactobacillus acidophilus Rosell-52:__ is a natural resident of the intestinal microflora; this specific strain from OptiBac has been well studied to survive gastric acidity and bile salts expected at mealtimes and to reach the intestines without damage. - __Lactobacillus rhamnosus Rosell-11:__ is a natural component of the friendly bacteria in the intestines; this species is one of the most studied in the world of live cultures. L. rhamnosus Rosell-11 has been proven to resist bile and gastric acidity over pH 3 - therefore if taken at mealtimes (when pH is around 4), it will pass through the stomach without being damaged. Suitabale for vegetarians and vegans.