Demonstration of safety characteristics and effects on gut microbiota of Lactobacillus gasseri HMV18

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 flora.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 verified toxins,and cause no visible change in mice's organs.L.gasseri HMV18 might not colonize in mice's gut,but can significantly 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.

A new Lactobacillus gasseri strain HMV18 inhibits the growth of pathogenic bacteria

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 16 S 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 producedα-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.

Survivability of freeze-dried probiotic Pediococcus pentosaceus strains GS4,GS17 and Lactobacillus gasseri(ATCC 19992)during storage with commonly used pharmaceutical excipients within a period of 120 days

Objective: To examine the survivability and stability of probiotic strains in presence and absence of pharmaceutical excipients for a long period of time at(4 ± 1)℃.Methods: The survival rates of probiotic strains, Pediococcus pentosaceus GS4(MTCC12683)(NCBI HM044322), GS17(NCBI KJ608061) and Lactobacillus gasseri(ATCC 19992), were evaluated. Probiotic strains were lyophilized individually and in combination of excipients(sorbitol, ascorbic acid, fructose and skim milk). The preparation was monitored for 120 d storing at(4 ± 1)℃. During storage, all the preparations were evaluated for viability and stability of probiotic properties like lactic acid production, antimicrobial effect, water activity, and adherence to epithelial cells.Results: Sorbitol, ascorbic acid and skim milk favoured the viability of freeze-dried cells and sustained probiotic properties during storage. Without excipients(control group),strains showed percentage of survivability not more than 70% while strains with excipients survived for 73%–93% for a long period of time.Conclusions: Commonly used excipients can be considered as a vehicle for delivering active principle in probiotic formulation and for sustaining the viability and stability of probiotic strains for a period of 120 d.

Effects of Probiotic Lactobacillus gasseri Strains of Breast-Fed Infant in a Murine Model

The ingestion of probiotic lactic acid bacteria has been evaluated and noted that it has an effect on the balance of desirable microbiota in the gastrointestinal tract. Lactobacillus gasseri demonstrates good survival in the gastrointestinal tract, and it has been associated with a variety of probiotic activities and roles, including the reduction of fecal mutagenic enzymes, the production of bacteriocins and the stimulation of macrophages immunomodulation. The aim of the study was to evaluate the effects of a pool of L. gasseri strains isolated from the feces of breastfed infants added in the human milk of healthy women. The milk was both pasteurized and unpasteurized, to verify the cell cytotoxicity of macrophages and to quantify the production of immunologic mediators such as IL-4, IL-6, IFN-γ, TNF-α, NO and oxygen intermediary compounds （H2O2）. The administration of raw human milk and pasteurized human milk to infants is a regular, encouraged practice in units of intensive therapy （UITs） and our present investigation verified the beneficial effect of addition of a pool of L. gasseri to pasteurized human milk （PHML）. Our results show that probiotic supplementation helped to maintain cell viability, reduced IL-6 and IFN-γ production and stimulated TNF-α, NO, H2O2, IL-4 production. Nevertheless, the results indicate that the addition of lactobacillus to human milk was not a determinant in the production of TNF-α. L. gasseri added to breast milk did not present a cytotoxic risk, and the addition ofL. gasseri to pasteurized milk of human milk bank would benefit newborns that depend on milk banks for the colonization of more desirable microbiota.

Lactobacillus gasseri LA39 promotes hepatic primary bile acid biosynthesis and intestinal secondary bile acid biotransformation

A growing body of evidence has linked the gut microbiota to liver metabolism.The manipulation of intestinal microflora has been considered as a promising avenue to promote liver health.However,the effects of Lactobacillus gasseri LA39,a potential probiotic,on liver metabolism remain unclear.Accumulating studies have investigated the proteomic profile for mining the host biological events affected by microbes,and used the germ-free(GF)mouse model to evaluate host-microbe interaction.Here,we explored the effects of L.gasseri LA39 gavage on the protein expression profiles of the liver of GF mice.Our results showed that a total of 128 proteins were upregulated,whereas a total of 123 proteins were downregulated by treatment with L.gasseri LA39.Further bioinformatics analyses suggested that the primary bile acid(BA)biosynthesis pathway in the liver was activated by L.gasseri LA39.Three differentially expressed proteins(cytochrome P450 family 27 subfamily A member 1(CYP27A1),cytochrome P450 family 7 subfamily B member 1(CYP7B1),and cytochrome P450 family 8 subfamily B member 1(CYP8B1))involved in the primary BA biosynthesis pathway were further validated by western blot assay.In addition,targeted metabolomic analyses demonstrated that serum and fecalβ-muricholic acid(a primary BA),dehydrolithocholic acid(a secondary BA),and glycolithocholic acid-3-sulfate(a secondary BA)were significantly increased by L.gasseri LA39.Thus,our data revealed that L.gasseri LA39 activates the hepatic primary BA biosynthesis and promotes the intestinal secondary BA biotransformation.Based on these findings,we suggest that L.gasseri LA39 confers an important function in the gut‒liver axis through regulating BA metabolism.