The probiotic potential is strain specific. For a desired health effect there is a different strain. In man, the gut microbiota varies among different individuals. Thus, the dose of a probiotic strain(s) must vary among different persons.
Preliminary, the probiotic bacterium should be checked for its ability to attach the smooth surfaces of gut.Dose must be more than 5 log CFU in older people and high doses are recommended in patients because there are an inverse proportion between probiotics and pathgenic bacteria in gut.