CN112870232A

CN112870232A - Application of bifidobacterium lactis BL-99 in improving intestinal bacterial infection resistance and intestinal immunity

Info

Publication number: CN112870232A
Application number: CN202011369724.5A
Authority: CN
Inventors: 刘伟贤; 吉塞拉·阿德里安娜·怀斯; 卡洛琳·安妮卡·凡·鲁-鲍曼; 盖瑞特·施密特; 赵雯; 洪维鍊
Original assignee: Inner Mongolia Yili Industrial Group Co Ltd; Inner Mongolia Dairy Technology Research Institute Co Ltd
Current assignee: Inner Mongolia Yili Industrial Group Co Ltd; Inner Mongolia Dairy Technology Research Institute Co Ltd
Priority date: 2019-11-29
Filing date: 2020-11-30
Publication date: 2021-06-01
Also published as: CN112870233A; WO2022110725A1

Abstract

The invention provides application of bifidobacterium lactis BL-99 in improving intestinal bacterial infection resistance and intestinal immunity. Specifically, the invention provides an application of Bifidobacterium lactis (CGMCC) in preparing a composition for improving intestinal immunity, wherein the preservation number of the Bifidobacterium lactis is CGMCC No. 15650. The invention discovers that the single strain can obviously improve the infection resistance of the intestinal bacteria, resist the invasion of pathogenic bacteria in an intestinal system, maintain the shielding function of the intestinal tract and/or prevent diarrhea caused by the pathogenic bacteria.

Description

Application of bifidobacterium lactis BL-99 in improving intestinal bacterial infection resistance and intestinal immunity

Technical Field

The invention relates to the technical field of microorganisms, in particular to a new application of Bifidobacterium lactis (Bifidobacterium lactis) BL-99 (preservation number CGMCC No.15650) in improving intestinal bacterial infection resistance and intestinal immunity.

Background

The intestinal epithelium is the first barrier of the body against pathogenic bacteria. Adhesion or invasion of pathogenic bacteria to epithelial cells stimulates the production of inflammatory or chemotactic factors by the intestinal epithelial cells. Some soluble mediators can modulate the intestinal immune system or induce cellular innate immune responses. Proper immune response and good epithelial barrier function will help protect the host from infection by pathogenic bacteria.

Probiotics refer to a group of living microorganisms that can produce a benefit to human health when ingested in sufficient quantities. Probiotics, which are important components of the intestinal microbiome, play important roles in human health, such as nutrition supply, vitamin synthesis, and contribution to digestion, angiogenesis and enteric nerve function promotion.

Disclosure of Invention

The invention aims to provide a new application of bifidobacterium lactis BL-99.

The invention provides Bifidobacterium lactis (Bifidobacterium lactis) which is named as BL-99 in the invention. The strain has been preserved in China general microbiological culture Collection center (CGMCC) (address: No. 3 Xilu-Beijing province No.1, Beijing Korean district, Ministry of China microbiology institute) 26.04.2018, and is named after classification: bifidobacterium lactis (Bifidobacterium lactis); the preservation number is CGMCC No. 15650. The Bifidobacterium lactis (Bifidobacterium lactis) provided by the invention has gastric acid resistance and intestinal juice resistance, the survival rate of viable bacteria is more than 62% when the Bifidobacterium lactis is treated in gastric acid solution with the pH of 2.5 for 30min, and the survival rate of viable bacteria is more than 61% when the Bifidobacterium lactis is treated for 2 hours; the survival rate of viable bacteria is more than 70 percent after the intestinal juice with the pH value of 6.8 is treated for 2 hours.

In the present invention, functional studies of Bifidobacterium lactis BL-99 for improving intestinal immunity were carried out using Enterotoxigenic Escherichia coli (Enterotoxichia coli) ETEC H10407 and Enterotoxigenic Escherichia coli (Enterobacter Enterotoxigenic Escherichia coli) EPEC O119 as pathogenic bacterial strains inducing intestinal infection in vitro. Coli are common pathogenic bacteria, including infantile diarrhea, traveller's diarrhea, and in developing countries or in poorly hygienic areas. ETEC H10407 is a relatively mature and common model strain for experiments, and is also often used for evaluating the adhesion capability of probiotics to pathogenic bacteria and inflammation signal pathways.

The study of the invention finds that the bifidobacterium lactis BL-99 (namely the bifidobacterium lactis with the preservation number of CGMCC No.15650) strain has the effect of inhibiting the adhesion of intestinal pathogenic bacteria, can obviously inhibit the adhesion of ETEC H1407 and EPEC O119 to Caco-2 cells, improves the integrity of an intestinal barrier, has the effect of inhibiting the generation of intestinal inflammatory factors, and can relieve the inflammatory reaction caused by ETEC H10407.

Therefore, the invention provides the application of Bifidobacterium lactis (Bifidobacterium lactis) in preparing the composition for improving the intestinal immunity, wherein the preservation number of the Bifidobacterium lactis is CGMCC No. 15650.

According to a particular embodiment of the invention, in the use of the invention, the bifidobacterium lactis is used for preparing the composition in the form of a solid or liquid preparation of viable and/or dead bacteria.

According to a specific embodiment of the present invention, in the application of the present invention, the improving the intestinal immunity comprises: improving intestinal bacterial infection resistance, resisting pathogenic bacteria invasion in intestinal system, maintaining intestinal shielding function, and/or preventing diarrhea caused by pathogenic bacteria.

According to a specific embodiment of the present invention, in the application of the present invention, the improving the intestinal immunity comprises: reducing the adhesion capability of pathogenic bacteria to the intestinal epithelial cells, and/or reducing the release of inflammatory factors IP-10 caused by the pathogenic bacteria to the intestinal epithelial cells.

According to a specific embodiment of the invention, in the use of the invention, the bifidobacterium lactis is applied in an amount of 1.0 × 10³CFU～1.0×10¹²CFU/day, or 0.001 μ g-1000 mg/day based on the weight of the thallus. Preferably, the application amount of the bifidobacterium lactis is 10⁷CFU～10¹¹CFU/day, or 10 mug-100 mg/day of thallus weight. The application amount of the Bifidobacterium lactis is 1.0 × 10³CFU～1.0×10¹²CFU/day, or 0.001 μ g-1000 mg/day based on the weight of the thallus.

According to a particular embodiment of the invention, the composition may comprise a food composition, a feed composition or a pharmaceutical composition.

According to a particular embodiment of the invention, the composition can be used in animals or humans. The composition may further comprise conventional ingredients in the art. For example, for pharmaceutical compositions, suitable excipients may be included, which may be excipients, diluents, fillers, absorption enhancers, and the like. For food compositions, the bifidobacterium lactis of the invention may be produced as in the prior art with bifidobacterium lactis-containing food products, the compositions being available in different forms depending on the needs of the recipient. Such as powders, lozenges, granules, microcapsules, liquid preparations, and the like.

In a specific embodiment of the invention, the composition is a food composition, and the food may be a liquid beverage, a solid beverage, an oral liquid, a dairy product, a tablet or a capsule, and may be, for example, a fermented dairy product (e.g., fermented milk, flavored fermented milk, fermented milk beverage, etc.), a cheese, a milk-containing beverage, a probiotic solid beverage, or a powdered milk, etc.

In another specific embodiment of the invention, the composition is a feed composition. The other components of the feed composition may be selected with reference to conventional techniques in the field of probiotic feeds.

In another specific embodiment of the present invention, the composition is a pharmaceutical composition. The other components of the pharmaceutical composition may be selected with reference to conventional techniques in the field of probiotic medicine.

In conclusion, the invention provides the new application of the bifidobacterium lactis BL-99, the bifidobacterium has the effects of remarkably reducing the adhesion capability of pathogenic bacteria to intestinal epithelial cells, improving the intestinal barrier function and activating the intestinal immunity, can be used for preparing foods, medicines, feeds and the like with the effects of resisting infection and regulating the intestinal health and the immunity, and has wide application prospect.

Drawings

FIG. 1 shows the results of the viable count determination of Bifidobacterium lactis BL-99.

FIG. 2 shows the effect of Bifidobacterium lactis BL-99 in inhibiting the adhesion of E.coli ETEC H10407 to Caco-2 (p < 0.05).

FIG. 3 shows the effect of Bifidobacterium lactis BL-99 in inhibiting the adhesion of pathogenic E.coli EPEC O119 to Caco-2 (p < 0.001).

FIG. 4 shows the effect of Bifidobacterium lactis BL-99 in reducing the induction of IP10 production by E.coli ETEC H10407 which is enterotoxic (p < 0.001).

Microbial preservation of the patent procedure:

bifidobacterium lactis BL-99 of the present invention:

the preservation date is as follows: 26/04/2018;

the preservation unit: china general microbiological culture Collection center (CGMCC);

the address of the depository: xilu No.1 Hospital No. 3, the institute of microbiology, China academy of sciences, Beijing, Chaoyang

The preservation number is: CGMCC No. 15650;

and (3) classification and naming: bifidobacterium lactis (Bifidobacterium lactis).

Detailed Description

For a more clear understanding of the technical features, objects and advantages of the present invention, reference is now made to the following detailed description taken in conjunction with the accompanying specific embodiments, and the technical solutions of the present invention are described, it being understood that these examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention. In the examples, the experimental methods in which specific conditions are not noted are conventional methods and conventional conditions well known in the art, or conditions as recommended by the instrument manufacturer.

Bifidobacterium lactis BL-99

The bifidobacterium lactis BL-99 is separated from the intestinal tract of the infant. The strain has been preserved in China general microbiological culture Collection center (CGMCC) (address: No. 3 Xilu-Beijing province No.1, Beijing Korean district, Ministry of China microbiology institute) 26.04.2018, and is named after classification: bifidobacterium lactis (Bifidobacterium lactis); the preservation number is CGMCC No. 15650.

1. Taxonomical characterization of Bifidobacterium lactis BL-99

The results of the physical and chemical experiments are shown in Table 1.

TABLE 1

Experimental project	Results	Experimental project	Results
				Gram stain	Positive for	Carbohydrate acid production (continuation)
Cell shape	Rod-like, polymorphic	Ribose	+
				Form spores	-	Trehalose	-
Contact enzyme	-	Xylose	+
				Oxidase enzyme	-	Maltose	+
Growth in air	-	Lactose	+
				Anaerobic growth	+	Cotton seed candy	+
Acid production from carbohydrates		Sorbitol	-
				Mannose	-	Melibiose	+
Melezitose	-	Galactose	+
				Fructose	-	Mannitol	-
Salicin	+	L-arabinose	-
				Inulin	-	Sodium gluconate	-
Cellobiose	-	Sucrose	+
				Starch	+

2. Tolerance of bifidobacterium lactis BL-99 to artificial gastric juice and intestinal juice

Bifidobacteria are genera that are generally not acid-fast. In this example, the tolerance of bifidobacterium lactis BL-99 of the present invention to artificial gastric juice and intestinal juice was tested, and bifidobacterium lactis which had been recognized in the art as having excellent acid resistance and survived through the gastrointestinal tract

For comparison.

The test method comprises the following steps: culturing Bifidobacterium lactis BL-99 strain in MRS liquid culture medium at 37 deg.C for 16 hr, centrifuging at 4 deg.C and 2500rpm for 10min, and collecting thallus.

Respectively culturing the strains to be tested in artificial gastric juice and artificial small intestine juice, processing at 37 ℃ for 0, 30min and 2h, and then performing viable count analysis to evaluate the acid resistance and intestinal juice resistance of the strains according to the survival rate. Survival rate (viable cell count after treatment/viable cell count at time 0) × 100%.

The survival rate detection result of the bacterial strain in artificial gastric acid (pH2.5) is shown in Table 2, the survival rate of the viable bacteria is 7.04% when BB-12 is treated in the artificial gastric acid (pH2.5) for 30min, and the survival rate of the viable bacteria is only 1.64% after 2 hours of treatment; the survival rate of the live bacteria of the bifidobacterium lactis BL-99 is 62.60 percent when the bifidobacterium lactis BL-99 is treated in artificial gastric acid (pH2.5) for 30min, and the survival rate of the live bacteria is 61.83 percent when the bifidobacterium lactis BL-99 is treated for 2 hours. The bifidobacterium lactis BL-99 disclosed by the invention has excellent gastric acid resistance and can smoothly pass through the stomach to reach the intestinal tract to play a probiotic role.

TABLE 2 survival of the strains in artificial gastric acid (pH2.5)

The survival rate of the strain in the artificial small intestine solution (pH6.8) is determined and shown in Table 3. The data show that the viable bacteria survival rate of BB-12 in artificial small intestine solution (pH6.8) for 2 hours is only 28.95%; the viable bacteria survival rate of the bifidobacterium lactis BL-99 is 70.23 percent when the bifidobacterium lactis BL-99 is treated in artificial gastric acid (pH2.5) for 2 hours. The bifidobacterium lactis BL-99 disclosed by the invention has excellent intestinal juice resistance and can survive and colonize in intestinal tracts.

TABLE 3 survival rate of the strains in artificial intestinal juice (pH6.8)

3. Toxicity experiment and safety detection of bifidobacterium lactis BL-99

Inoculating the bifidobacterium lactis BL-99 of the invention into a BBL liquid culture medium, carrying out anaerobic culture for 48 +/-2 hours at 36 +/-1 ℃, and counting the viable count of the bifidobacterium lactis BL-99 in the culture solution to be 3.7 multiplied by 10⁸cfu/mL, stock solutions and 5-fold concentrates of the cultures were continuously gavaged to 20.0mL/kg BW for 3 days and observed for 7 days. The experiment was performed with a control group of 5-fold concentrated solution and a stock solution of the culture medium. The experimental results show that: the BBL culture stock solution and 5-fold concentrated solution of Bifidobacterium lactis BL-99 had no statistical effect on the weight gain of mice (p > 0.05) compared with the respective control group, and no toxic reaction or death of the tested mice was observed.

The antibiotic sensitivity of the bifidobacterium lactis BL-99 is evaluated by adopting an SN/T1944-2007 method of determination of bacterial resistance in animals and products thereof. The evaluation results show that the bifidobacterium lactis BL-99 is sensitive to Ampicillin Ampicillin, penicillin G Penicillin G, Erythromycin Erythromycin, Chloramphenicol Chloramphenicol, Clindamycin Clindamycin, Vancomycin Vancomycin, Tetracycline and the like. Meets the requirements of European Food Safety Authority (European Food Safety Authority) on the evaluation specification of the resistance of the edible bacteria. The bifidobacterium lactis BL-99 does not contain exogenous antibiotic resistance genes and is safe to eat.

4. Determination of viable cell count of Bifidobacterium lactis BL-99 used in examples

Bifidobacterium lactis BL-99 (preservation number: CGMCC No.15650), picking out single colony by plate coating method, identifying 16S, and freezing and preserving at-80 deg.C in glycerol tube. The strains were cultured in MRS medium at 37 ℃ before the experiment. The strain is enriched by a centrifugal culture medium from growth to logarithmic phase. Viable cell count and bacterial activity were measured by fluorescence cell sorting (FACS), and the results are shown in FIG. 1. The number of viable bacteria of the strain used in each embodiment of the invention is 1 multiplied by 10⁸CFU/mL and 1X 10⁶CFU/mL。

5. Example data analysis

All data in the experiment were repeated at least 3 times and the results were expressed as mean ± standard deviation; data analysis was performed using SPSS17.0 software (SPSS, Chicago, IL, USA), significance analysis was performed using the method of LSD for one-way anova, P-value <0.05 was considered to have statistically significant differences according to: p <0.05, p <0.01, p <0.001, p < 0.0001. The graph was plotted using GraphPad Prism 5.0.

Example 1 measurement of anti-adhesive Capacity

Whether the bifidobacterium BL-99 has Caco-2 adhesion resistance to ETEC H10407 and EPEC O119 is researched by adopting a co-culture method. Caco-2 cells were seeded in 24-well plates and cultured. Caco-2 cells were washed with PBS buffer and the strain and Caco-2 cells were co-cultured for 1 h. ETEC H10407 and EPEC O119 were measured at multiplicity of infection (MOI) 50: 1 is added into Caco-2 cells to be co-cultured for 1h (37 ℃), and the final viable count is 1 multiplied by 10⁷CFU/mL. The Caco-2 group to which Bifidobacterium-free BL-99 had been added was used as a negative control. 1mM Zinc Oxide (ZnO) was used as a positive control group instead of Bifidobacterium BL-99. After incubation, the Caco-2 cells were washed and lysed, and then the pathogen was inoculated on agar. After overnight incubation on agar plates at 37 ℃, CFU colonies of bacteria were counted to measure pathogen adsorption.The number of growing E.coli colonies was counted and recorded as CFU/mL. In parallel to the anti-adhesion test, Escherichia coli (final concentration of) 10⁷CFU/mL was added to 1mL of the test substance (BL-99 bacterial solution), and co-cultured at 37 ℃ for 1 hour to measure the activity. After incubation, E.coli was harvested from each sample by centrifugation, resuspended in PBS, and plated on agar plates. After overnight incubation on agar plates at 37 ℃, CFU colonies of bacteria were counted to measure pathogen adsorption. The number of growing E.coli colonies was counted and recorded as CFU/mL.

Experiment by taking human intestinal cells Caco-2 as a model, the invention proves that the bifidobacterium BL-99 has an inhibiting effect on enterotoxigenic escherichia coli ETEC H10407 and enteropathogenic escherichia coli EPEC O119.

In some of the inventive runs, 10⁸The experimental results of the inhibitory ability of bifidobacterium BL-99 at CFU/mL concentration on ETEC H10407 are shown in FIG. 2. Under the condition of no intervention of bifidobacterium BL-99, the adhesion number of enterotoxigenic escherichia coli ETEC H10407 to Caco-2 cells is as high as 3.75 multiplied by 10⁶CFU/mL (6.57log CFU/mL). When Escherichia coli ETEC H10407 and Bacillus bifidus BL-99 act together, the number of adhered ETEC H10407 is 7.67 × 10⁵CFU/mL (5.88log CFU/mL), the inhibition was 10.8%.

In some of the inventive runs, 10⁸The experimental results of the inhibitory ability of Bifidobacterium BL-99 at CFU/mL concentration on EPEC O119 are shown in FIG. 3. Under the condition of no intervention of bifidobacterium BL-99, the adhesion number of enterotoxigenic escherichia coli ETEC H10407 to Caco-2 cells is as high as 2.34 multiplied by 10⁶CFU/mL (6.37log CFU/mL). When Escherichia coli ETEC H10407 and Bacillus bifidus BL-99 act together, the number of adhered ETEC H10407 is 4.5 × 10⁵CFU/Ml (5.65log CFU/mL), inhibition was 11.29%.

In further experiments of batches of the present invention, 10 runs were made⁶CFU/mL and 10⁸CFU/mL of Bifidobacterium BL-99 at two different concentrations was tested for inhibition of E.coli EPEC O119 adhesion to Caco-2 cells. Therein, 10⁸Two separate experimental determinations of CFU/mL concentration were made. Data of experimental results (mean. + -. standard error, weight)Three more measurements) are shown in table 4. After comparing the negative control with the test group using the Dunnett's posthoc test, 10 were found in the experimental group 1⁶BL-99 at concentration significantly lower than the negative control (P)<0.05)；10⁸Probiotic BL-99 at concentrations has a tendency to reduce EPEC adhesion. In Experimental group 2, 10⁸BL-99 at concentrations significantly reduced pathogen adherence (P)<0.01)。

TABLE 4

The experimental results show that the bifidobacterium lactis BL-99 has an inhibiting effect on enterotoxigenic escherichia coli ETEC H10407 and enteropathogenic escherichia coli EPEC O119.

Example 2 intestinal Barrier integrity test

The ideal small intestinal epithelial barrier function is a prerequisite to protect the host from pathogenic invasion and/or pathogenic toxins. In this study, barrier integrity in vitro was demonstrated by measuring the transepidermal electrical resistance (TEER) of the intestinal cell layer. To investigate the effect of probiotics on infection, the TEER was determined as a function of time before and after infection with e.

Caco-2 cells were seeded into Transwell polycarbonate cell culture inserts with an average pore size of 0.4um and an area of 0.33cm²Until complete differentiation (± 1000 Ω). Trans-epithelial electrical resistance (TEER) was measured with an EVOM2 epidermal voltmeter purchased from a world precision instrument to measure barrier integrity.

On the day of testing, cells were washed and cultured in medium without antibiotics and serum, but containing the test substance, for 1 hour at 37 ℃. Immediately thereafter, E.coli was added to the test substance (the infection magnification MOI was 200:1) and cultured for 6 hours. TEER was measured 1 hour, 2 hours, 3 hours, 4 hours and 6 hours after exposure of the test substance and before addition of the pathogen before the start of the experiment (t ═ 1), and 1 hour, 2 hours, 3 hours, 4 hours and 6 hours after pathogen exposure, respectively. The TEER values under the individual conditions after exposure to a pathogen correlate with their TEER values at t ═ 0 and are expressed as Δ TEER (Ω. Cm 2). Negative controls (addition of E.coli only) and positive controls not exposed to pathogenic bacteria or test substances were also included in the experimental group. All conditions were assayed in triplicate and some controls were assayed in 6 replicates.

Table 5 records 10⁶Effect of probiotic BL-99 at CFU/mL concentration on transmembrane resistance TEER in case of exposure to escherichia coli ETEC H10407. Table 6 shows 10⁸Effect of probiotic BL-99 at CFU/mL concentration on transmembrane resistance TEER in case of exposure to escherichia coli ETEC H10407. Experimental data were measured in triplicate.

TABLE 5

TABLE 6

10⁶Bifidobacterium BL-99 at CFU/mL concentration tended to increase TEER value compared to the negative control at time points t 1 and t 2. 10⁸Bifidobacterium BL-99 at CFU/mL concentration tended to increase TEER values at various time points compared to the negative control.

Example 3 assay of immunomodulatory Capacity

The immunomodulatory capacity of Bifidobacterium lactis BL-99 is based on whether it reduces ETCT H10407 Caco-2 cell-induced IP-10(10kDa interferon-gamma-induced protein, IP10) production. Caco-2 cells were cultured in 96-well plates to appropriate abundance. At the beginning of the experiment, cells were washed once with medium without antibiotics. The monolayer cells were co-cultured with the test substance at 37 ℃ for 1 hour in a medium containing no antibiotic, and this was repeated three times. Coli stimulating cells (MOI 200:1) were added. After 1 hour incubation, the monolayer cells were co-cultured with the pathogens and rinsed and incubated overnight with medium containing the test substance and 50 μ g/mL gentamicin. As a Blank control (Blank), only culture medium was used without stimulation with E.coli. Culture broth stimulated with E.coli but without test substance was used as a control for E.coli response. In addition, as a control for Caco-2 cell response, cells were stimulated with a mixture of cultures containing Rec TNF α (10ng/mL) and Rec IFN γ (5ng/mL), both purchased from R & D systems of Abindion, UK. Supernatants were collected after 24 hours of stimulation and stored at-20 ℃. IP-10 was tested using the Bio-Plex kit (BioRad, Calif., USA) according to the manufacturer's instructions.

The experimental results are expressed as mean ± standard deviation; data analysis was performed using SPSS17.0 software (SPSS, Chicago, IL, USA), significance analysis was performed using the method of LSD for one-way anova, P-value <0.05 was considered to have statistically significant differences according to: p <0.05, p <0.01, p < 0.001. The graph in the article is drawn using GraphPad Prism 5.0.

10⁸The results of the reduction of IP10 by CFU/mL concentration of Bifidobacterium lactis BL-99 are shown in FIG. 4. The addition of ETEC H10407 to the Caco-2 cell model caused the remarkable up-regulation of IP10, the content of IP10 in a cell culture solution reaches 656.52 +/-57.11 pg/mL, the blank group of Caco-2 cells are not treated at all, and the content of IP10 in a cell culture supernatant is 162.29 +/-21.28 pg/mL. After the bifidobacterium BL-99 is added for acting for 1 hour, the content of IP10 in the cell culture solution supernatant is low and is 146 +/-7.74 pg/mL. Shows that the bifidobacterium BL-99 can inhibit the generation of an inflammatory factor IP10 and obviously inhibit inflammatory reaction (p) caused by ETEC H10407<0.001), further indicating that BL-99 has the potential to reduce the inflammatory response of ETEC 10407 to some extent.

Interferon gamma inducible protein 10(IP10) plays an important role in the development of UC. IP10 belongs to ELR negative CXC subfamily of endogenous chemokines, is induced by IFN-gamma and secreted by various cells such as fibroblasts, endothelial cells, monocytes, T lymphocytes, etc., and also secreted by lipopolysaccharide, pro-inflammatory factors such as IFN-alpha/beta and TNF-alpha, etc. CXCR3 is the only receptor of IP10, and after IP10 binds specifically to CXCR3, it can promote the chemotactic activity of CXCR3+ cells, thus triggering a multi-step signal transduction pathway, and chemotactic CXCR3 positive target cells such as T cells, B cells, monocytes/macrophages, dendritic cells, NK cells and the like to local inflammatory foci. Wherein the recruited T cells, upon activation, secrete mainly IL-2, TNF- β, IFN- γ; macrophages mainly secrete inflammatory factors such as TNF-alpha, IL-1 beta, IL-6, IL-18, IL-12, IL-23, IFN-gamma and the like; on one hand, inflammatory factors such as TNF-alpha, IFN-gamma and the like with increased local secretion stimulate to generate more IP10, further recruit more immune cells and form a malignant cycle; on the other hand, the intestinal mucosa barrier can be directly or indirectly damaged, so that the intestinal mucosa is damaged, and the occurrence and development of ulcerative colitis are promoted.

The results of the above studies confirm that: bifidobacterium lactis BL-99 can remarkably adhere ETEC H1407 and EPEC O119 to Caco-2 cells, and relieve inflammatory reaction caused by ETEC H10407. The bifidobacterium lactis BL-99 has good potential for preventing infantile diarrhea, traveler's diarrhea, intestinal inflammation and the like.

Claims

1. Application of Bifidobacterium lactis (CGMCC) in preparing composition for improving intestinal immunity is disclosed, wherein the preservation number of the Bifidobacterium lactis is CGMCC No. 15650.

2. Use according to claim 1, wherein the bifidobacterium lactis is used for preparing the composition in the form of a solid or liquid preparation of viable and/or dead bacteria.

3. The use of claim 1, wherein the enhancing intestinal immunity comprises: improving intestinal bacterial infection resistance, resisting pathogenic bacteria invasion in intestinal system, maintaining intestinal shielding function, and/or preventing diarrhea caused by pathogenic bacteria.

4. The use of claim 1, wherein the enhancing intestinal immunity comprises: reducing the adhesion capability of pathogenic bacteria to the intestinal epithelial cells, and/or reducing the release of inflammatory factors IP-10 caused by the pathogenic bacteria to the intestinal epithelial cells.

5. Use according to claim 3 or 4, wherein the pathogenic bacterium is Escherichia coli.

6. Use according to claim 5, wherein the E.coli comprises enterotoxigenic E.coli ETEC H10407 and/or pathogenic E.coli EPEC O119.

7. The use according to claim 3 or 4, wherein the Bifidobacterium lactis is used in an amount of 1.0 x 10³CFU～1.0×10¹²CFU/day, or 0.001 μ g-1000 mg/day based on the weight of the thallus.

8. Use according to claim 7, wherein the Bifidobacterium lactis is administered in an amount of 10⁷CFU～10¹¹CFU/day, or 10 mug-100 mg/day of thallus weight.

9. Use according to claim 1, wherein the composition comprises a food composition, a feed composition or a pharmaceutical composition.

10. Use according to claim 9, wherein the food product is a liquid beverage, a solid beverage, an oral liquid, a dairy product, a tablet or a capsule.