Preclinical testing in the development of probiotics: a regulatory perspective with Bacillus strains as an example

Preclinical testing of the microbial strains is the first important step in the development of probiotics. Requirements for the set of tests can vary depending on the bacterial species and the expected mechanism of action in the organism. Common approaches to preclinical testing of probiotic strains include strain identification (i.e., determination of phenotypic and genotypic properties), safety evaluation (i.e., characterization of history of use [safety contact], assessment of resistance to antibiotics, and evaluation of pathogenic properties in vitro and in animal models), and efficacy testing (i.e., functional characterization). Future progress in probiotics requires more studies to determine the mechanisms of their action, as well as an understanding of the basis and mechanisms of pathogenicity for different probiotic strains. Special attention should be given to recombinant probiotics, particularly in the formulation of criteria for selection of the host strain, for assessment of environmental safety, and for tracing the fate of recombinant DNA in vitro and in vivo.