A 90-day oral toxicity study on a new strain of Lactobacillus paracasei in rats

Lactobacillus paracasei is a species of bacteria that has been suggested to have probiotic benefits. To investigate the subchronic toxicity of L. paracasei GW080, a 90-feeding study was conducted in rats. Sprague–Dawley rats were randomly divided into four groups (10 rats/sex/group) and treated with 0, 1.25, 2.5, and 5.0 g/kg body weight (approximately equivalent to 0, 2.5 × 109, 5.0 × 109 and 1 × 1010 cfu/kg bw) of test material by gavage for 90 days. Daily clinical observations and weekly measurement of body weights and food consumption were conducted. Blood samples were obtained on day 46 and day 91 for the measurement of hematology and clinical chemistry parameters. Animals were euthanized for necropsy. Selected organs were weighted and recorded. Histological examination was performed on all tissues from animals in the control and high dose groups. No mortality, body weight, food consumption or treatment-related findings in clinical observations, macroscopic or microscopic examinations were observed. Differences between treated and control groups in some hematology and clinical chemistry parameters were not considered treatment-related. The no-observed-adverse-effect-level (NOAEL) for L. paracasei GM080 was considered to be 5.0 g/kg body weight (approximately equivalent to 1 × 1010 cfu/kg bw) for both genders, the highest dose tested.