In vitro selection of probiotic lactobacilli: a critical appraisal

The problem of choosing criteria for the in vitro selection of lactobacilli to be used as health-promoting, probiotic ingredients, in food and pharmaceutical preparations, was apparent even in the original works of Metchnikoff, who first proposed the therapeutic use of these bacteria. In the last decade, a consensus has been reached by scientists on some criteria, with particular attention being paid to the ecological origin of the bacteria, their tolerance to the hostile conditions of the stomach and the small intestine, and their ability to adhere to intestinal surfaces. Even though these criteria have been used to select probiotic lactobacilli, some doubts still remain about the real value of these criteria. A critical rethinking of selection criteria seems necessary in order to improve the process of developing better probiotics.