# Safety Assessment and Probiotic Potential of a Novel Species Lactobacillus xujianguonis

## TL;DR

This study evaluates the safety of a new Lactobacillus species, Lactobacillus xujianguonis, for use as a probiotic, finding it safe in preclinical tests.

## Contribution

The paper presents the first preclinical safety assessment of Lactobacillus xujianguonis for potential probiotic use.

## Key findings

- L. xujianguonis strains showed probiotic traits like acid/bile tolerance and antimicrobial activity.
- No mortality or organ toxicity was observed in mice after acute or subchronic oral exposure.
- No adverse effects on inflammatory markers or intestinal tissue were detected.

## Abstract

Background: Some lactobacilli strains have been documented to cause bacteremia and sepsis in immunocompromised or critically ill hospitalized patients, challenging the universally presumed safety of lactobacilli. Therefore, strain-specific risk assessments are required for the use of Lactobacillus as a probiotic. Lactobacillus xujianguonis, a novel Lactobacillus species isolated from Marmota himalayana, has probiotic potential but lacks safety data. Objective: To evaluate the preclinical safety of L. xujianguonis for food-grade use. Methods: Systematic safety assessment includes in vitro studies and oral toxicity studies. In vitro studies encompassed gastrointestinal tolerance, auto-aggregation and pathogen inhibition, antibiotic susceptibility, and hemolysis/gelatinase activity assays. Oral toxicity studies contained acute single-dose and repeated-dose 28-day oral toxicity studies in mice based on the OECD toxicity study guidelines. Results: L. xujianguonis strains HT111-2 and 06-2 demonstrated certain probiotic traits, including high acid/bile tolerance, strong auto-aggregation, and antimicrobial activity against common human gastrointestinal pathogens. In vitro safety assessments showed susceptibility to nine antibiotics and absence of hemolytic/gelatinase activity. Acute oral exposure (1 × 1011 CFU/kg) induced no mortality, clinical abnormalities, or organ toxicity. Subchronic 28-day administration (multiple doses) showed absence of adverse clinical signs with body weight stability and no hematological, biochemical, or histopathological deviations in C57BL/6 mice. Inflammatory and immunological markers remained unaffected. Histological staining results and transcriptional level validation revealed no evidence of intestinal tissue damage. Conclusions: This study provides preliminary evidence of the safety of L. xujianguonis, supporting its advancement to functional research.