Human normal flora is a source of probiotics. The safety characteristics of a specific isolate determine its application in foods or drugs. The food-borne-pathogen antagonist strain Lactobacillus gasseri HMV18 is one of the isolates from normal human f lora. In this work, we assessed the in vitro pH tolerance, bile tolerance, biogenic amine production, mucin utilization, and safety of in vivo administration to mice to evaluate general health, organ-body weight index, organ histopathological change, whether L. gasseri HMV18 can colonize in the gut or modulate the gut microbiota after oral administration. The results suggest that L. gasseri HMV18 can tolerate pH 3 for 2 h, 3% bile for 3 h, biogenic amine negative, mucin usage negative, does not encode verif ied toxins, and cause no visible change in mice’s organs. L. gasseri HMV18 might not colonize in mice’s gut, but can signif icantly affect the structure of gut microbiota. A bibliographical survey suggested that there were as few as 8 opportunistic infection cases from 1984 to 2022 and that the possibility for L. gasseri to cause infection is relatively low. Therefore, this work provides a basis for the foods or drugs application of L. gasseri HMV18 and gives a map of experiments for the safety assessment of probiotics.

To search for a new eco-friendly therapy for infectious disease caused by Escherichia coli, Staphylococcus aureus or Klebsiella oxytoca, we collected the vaginal swabs from healthy women, screened for Lactobacillus and found a strain repressing the growth of pathogenic bacteria. The new isolate was identified as L. gasseri by the colony morphology, Gram staining, biochemical reactions and confirmed by the 16S rDNA sequencing. The HMV18 strain inhibited the growth of food-borne pathogens such as E. coli, S. aureus and K. oxytoca. The HMV18 strain was sensitive to penicillin, ampicillin, erythromycin, tetracycline and chloramphenicol. The HMV18 strain produced α-hemolysis. Pathological histology of the mice ileum showed that the mucosa, villi, lamina propria and crypt depth remained intact and there was no inflammation or hyperemia in the L. gasseri HMV18 gavaged group. L. gasseri HMV18 could not up-regulate inflammatory cytokines level of plasma. All the results suggested L. gasseri HMV18 is a candidate probiotic to be an additive for food preservation or drug to prevent food-borne diseases.