Oral toxicity evaluation of <i>Bacillus clausii</i> 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 <i>Bacillus clausii</i> M31, isolated from children's feces, in Swiss rats and New Zealand rabbits. To investigate acute toxicity, rats were given varied doses of <i>B. clausii</i> M31 (1 × 10¹¹ CFU/mL, 3 × 10¹¹ CFU/mL, and 5 × 10¹¹ 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 × 10¹¹ CFU/mL) or a high dose (5 × 10¹¹ 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 <i>B. clausii</i> M31 at concentrations up to 5 × 10¹¹ CFU/mL for 28 days poses no discernible risks.