Safety Evaluation by Phenotypic and Genomic Characterization of Four Strains with Probiotic Properties.

Probiotic species are known to exert health benefits in hosts when administered in adequate quantities. A systematic safety assessment of the strains must be performed before the strains can be designated as probiotics for human consumption. In this study, we selected IDCC 3901, IDCC 3101, IDCC 3801, and IDCC 3551 as representative probiotic strains and investigated their probiotic properties and potential risks through phenotypic and genomic characterization. Various assays including antimicrobial resistance, biogenic amine production, L-/D-lactate production, acute oral toxicity, and antipathogenic effect were performed to evaluate the safety of the four strains. Genomic analysis using whole genome sequencing was performed to investigate virulence and antibiotic resistance genes in the genomes of the selected probiotic strains. The phenotypes of the strains such as enzymatic activity and carbohydrate utilization were also investigated. As a result, antibiotic resistances of the four species were detected; however, neither antibiotic resistance-related genes nor virulence genes were found by genomic analysis. Moreover, the four species did not exhibit hemolytic activity or β-glucuronidase activity. The biogenic amine production and oral acute toxicity were not shown in the four species, whereas they produced D-lactate with minor ratio. The four species exhibited antipathogenic effect to five pathogenic microorganisms. This study provides a way to assess the potential risks of four different species and validates the safety of all four strains as probiotics for human consumption.