Safety evaluation of a heat-treated <i>Bifidobacterium bifidum </i>OLB6378 concentrate

Several bacterial strains, including probiotic strains, have undergone evaluations for their safety and potential beneficial health effects. Some of these strains have been introduced into various markets, including that for infant products. However, certain probiotic strains have been linked to serious infections in infants, such as septicemia and meningitis. Given this, it is crucial to assess the safety of each probiotic strain, including those of Bifidobacterium, which is a common genus of probiotics. One such strain, Bifidobacterium bifidum OLB6378 (NITE BP-31), referred to as OLB6378 hereafter, has been selected for use in infants. To determine its genotoxicity and general toxicity potential, a heat-treated OLB6378 concentrate was subjected to various tests, including the bacterial reverse mutation test, in vitro chromosome aberration test, in vivo micronucleus test, and single- and 90-day oral gavage toxicity studies in rats. No significant differences were observed compared with negative controls in any of genotoxicity tests. The single-dose toxicity study employed dose levels of 560, 1,693, and 5,092 mg/kg, representing the total solid contents of culture concentrates containing OLB6378 (equivalent to 8.1 × 1011, 2.4 × 1012, and 7.4 × 1012 cells/kg of Bifidobacterium, respectively). In the 90-day toxicity study, dose levels of 280, 853, and 2,546 mg/kg/day were used (equivalent to 4.0 × 1011, 1.2 × 1012, and 3.7 × 1012 cells/kg/day, respectively). Importantly, the heat-treated OLB6378 concentrate did not induce any signs of toxicity in any of the conducted toxicity studies. In conclusion, the heat-treated OLB6378 concentrate exhibited no genotoxicity potential, and the no-observed-adverse-effect level in the 90-day toxicity study was determined to be 2,546 mg/kg/day (equivalent to 3.7 × 1012 cells/kg/day). This suggests that heat-treated OLB6378 can be safely utilized as a food source.