Oral Toxicity Evaluation of M31 Isolated from the Children's Feces in the Northern Province of Vietnam

This study investigated the acute and repeated 28-day dose toxicity profiles of M31, isolated from children's feces, in Swiss rats and New Zealand rabbits. To investigate acute toxicity, rats were given varied doses of M31 (1 × 10 CFU/mL, 3 × 10 CFU/mL, and 5 × 10 CFU/mL) orally once daily for 14 days, in accordance with OECD recommendations No. 423. To evaluate toxicity, rabbits were given either a low dosage (1 × 10 CFU/mL) or a high dose (5 × 10 CFU/mL) during a 28-day period using the OECD Test Guideline 407 protocol. Neither death nor significant abnormalities were observed in the rats during the experiment. The microscopic examination of key organs revealed no substantial changes in organ morphology. Furthermore, analyses of serum biochemistry and hematological parameters did not reveal any treatment-associated variations. In sum, these findings suggest that the oral intake of M31 at concentrations up to 5 × 10 CFU/mL for 28 days poses no discernible risks.