Indigenous dadih lactic acid bacteria: cell-surface properties and interactions with pathogens

ABSTRACT:  Cell surface properties of dadih lactic acid bacteria strains were studied for adhesion to hydrocarbons (BATH) and aggregation abilities. Autoaggregation correlates with adhesion, which is a prerequisite for colonization and infection of the gastrointestinal tract by many pathogens, whereas coaggregation has been related to the ability to interact closely with pathogens. The results demonstrated significant differences in cell surface properties among the tested natural lactic acid bacteria food strains. Hydrophobicity increased when the cells were heat inactivated. All strains showed aggregation abilities with the pathogen strains tested, but the coaggregation properties were strain-specific. Our results indicate that the ability to autoaggregate, together with cell surface hydrophobicity and coaggregation abilities with pathogen strains, can be used for preliminary screening in order to identify potentially probiotic bacteria suitable for human or animal use. This study suggest the importance to identify and characterize bacterial cell-wall properties to understand their role in adhesion to hydrocarbons, autoaggregation and relation to coaggregation mechanisms, and also the relevance to future probiotic food development from natural strains.     

In vitro analysis of probiotic strain combinations to inhibit pathogen adhesion to human intestinal mucus

Competition with pathogens for adhesion and colonization of the mucosal surfaces are possible protective mechanisms of probiotics. In this study we evaluated the ability of commercial strains (Lactobacillus rhamnosus GG, L. rhamnosus LC705, B. breve 99 and Propionibacterium freudenreichii ssp. shermanii JS) each strain alone and in different combinations to inhibit, displace and compete with selected pathogens in order to test the influence of the presence of the other probiotic in the adhesion pathogens to immobilized mucus. The ability to inhibit the adhesion or to displace adhered pathogens was variable depending on both the probiotic combination and the pathogen tested. Our results demonstrate that different probiotic combinations were able to enhance the inhibition percentages to pathogen adhesion to intestinal mucus. All probiotic combinations tested in this study showed inhibition abilities against pathogen infection with values which were over 40% for some pathogens tested. Combinations had specific properties and inhibition abilities against some or all of the tested pathogens. These results suggest that combinations of probiotics strains could be useful and more effective in inhibition of pathogen adhesion. The inhibition and displacement profiles were very different suggesting that different mechanisms are implied in both processes. Selection of new probiotic combinations should be conducted for specific target pathogens or pathogen associated microbiota aberrancies.     

Aggregation and hydrophobicity properties of 6 dairy propionibacteria strains isolated from homemade Turkish cheeses

In the present study, 6 dairy Propionibacterium strains were assessed with regard to their hydrophobic characteristics and their autoaggregation and coaggregation abilities since these traits have been shown to be indicative of adherence in other microorganisms. Aggregation assays and bacterial adhesion to hydrocarbons demonstrated significant differences in cell surface properties among the tested propionibacteria strains. Almost all strains appeared relatively hydrophilic, which showed low affinity for p-xylene. Four of the tested strains showed the strong adhesion to ethyl acetate, a basic solvent, in comparison with microbial adhesion to chloroform, an acidic solvent, which demonstrated the particularity of propionibacteria to have an important electron donor and acidic character. Also, these strains simultaneously showed affinity to 3 hydrocarbons, suggesting a high complexity of the cell surface. All propionibacteria strains tested showed autoaggregation and coaggregation ability with the Escherichia coli ATTC 11229, but the results were strain-specific and dependent on incubation conditions. Anaerobic incubation conditions were determined as the best condition for aggregation abilities of propionibacteria strains. A relationship was obtained between aggregation abilities (auto- and coaggregation) and a correlation between adhesion to hydrocarbon (chloroform) and autoaggregation was possible. Our results indicate that the ability to autoaggregation together with cell surface hydrophobicity and coaggregation abilities with E. coli strain can be used for preliminary screening in order to identify potentially probiotic bacteria suitable for human or animal use. PRACTICAL APPLICATION: Autoaggregation, cell surface hydrophobicity, and coaggregation abilities with E. coli of the selected dairy propionibacteria strains could be used as probiotic in foods after in vivo studies.     

Adhesion abilities of dairy Lactobacillus plantarum strains showing an aggregation phenotype

Bacterial aggregation phenotype and cell surface hydrophobicity of dairy Lactobacillus plantarum strains were screened in order to assess a correlation with their adhesion and pathogen competitive exclusion abilities. Lactobacilli strains showing an aggregation phenotype, L. plantarum IFPL33, IFPL81, IFPL150, IFPL156 and IFPL162, also exhibited the highest percentages of autoaggregation (> 50%) at 24 h. In addition, autoaggregation abilities of the lactobacilli were highly correlated with their percentages of co-aggregation with all the pathogens tested, although co-aggregation properties were pathogen specific. Nevertheless, none of the autoaggregation and co-aggregation abilities correlated with the affinity to xylene (hydrophobicity) and the ability of adhesion to Caco-2 cells. Furthermore, these properties are not fully correlated with the ability of the lactobacilli strains for inhibiting pathogen adhesion. Aggregation abilities and cell surface hydrophobicity may not be the only components responsible for adhesion but some of the criteria to bear in mind of a complex mechanism that enables microorganisms to interact with the host and exert its beneficial effect. Further research is needed to identify remaining attributes related to adhesion and pathogen exclusion properties of potential probiotic strains.     

In vitro evaluation of Lactobacillus gasseri strains of infant origin on adhesion and aggregation of specific pathogens

Numerous Lactobacillus species are members of the normal healthy human intestinal microbiota, and members of the Lactobacillus family predominate among the current marketed probiotic strains. Most of the current commercial probiotic strains have not been selected for specific applications but rather have been chosen based on their technological properties. Often the ability of such strains to temporarily colonize the gastrointestinal tract may be lacking, and the interactions with intestinal microbiota are few. Furthermore, the competitive exclusion properties of potential probiotic bacteria are strain specific and vary greatly. Thus, it is highly desirable that new candidate probiotic isolates originate from the healthy target population. In this study, seven newly isolated strains of Lactobacillus gasseri originating from feces of a healthy newborn child were evaluated for their ability to adhere to intestinal mucus, to autoaggregate and coaggregate with the model pathogens Cronobacter sakazakii (ATCC 29544) and Clostridium difficile (1296). All the bacterial strains, single or in combination, in viable and nonviable forms, were able to autoaggregate. The coaggregation with C. sakazakii or C. difficile was higher (P < 0.05) in nonviable than in the viable forms. Single L. gasseri strains showed similar adhesion abilities to intestinal colon mucus. The seven L. gasseri strains when combined were also able to significantly compete with, displace, and inhibit the adhesion of C. sakazakii and C. difficile in the mucus model. This study demonstrates that the studied L. gasseri strains fulfill the basic adhesion and aggregation properties for probiotics and could be considered for potential future use in children.     

Investigating hydrophobicity and the effect of exopolysaccharide on aggregation properties of dairy propionibacteria isolated from Turkish homemade cheeses

Propionic acid bacteria have been used widely as starter cultures. However, their potential as probiotics has received little attention. The ability to auto- and coaggregate is a desirable property for probiotics in health-promoting foods. Therefore, in the current study, we assessed the effect of exopolysaccharides produced by dairy propionibacteria strains on the aggregative and hydrophobicity properties. All propionibacteria strains tested showed auto- and coaggregation ability with Escherichia coli ATCC 11229, but the results were strain specific and dependent on exopolysaccharides production and incubation conditions. In addition, propionibacteria strains tested were determined to be highly hydrophilic. Our results indicate that the ability to autoaggregate, together with cell-surface hydrophobicity and coaggregation abilities with an E. coli strain, can be used for preliminary screening in order to identify potentially probiotic bacteria suitable for human or animal use.     

Adhesion of selected Bifidobacterium strains to human intestinal mucus and the role of adhesion in enteropathogen exclusion

The ability of potential probiotic strains to adhere to the intestinal mucosa and exclude and displace pathogens is of utmost importance for therapeutic manipulation of the enteric microbiota. The ability of seven selected human bifidobacterial strains and five human enteropathogenic strains to adhere to human intestinal mucus was analyzed and compared with that of four strains isolated from chicken intestines. The adhesion of the bifidobacterial strains ranged from 3 to 16% depending on the strain. Bifidobacterium strains of animal origin adhered significantly better than did strains of human origin. Of the pathogenic bacteria, Escherichia coli NCTC 8603 had the highest adhesion value (20%), Salmonella Typhimurium ATCC 29631, Enterobacter sakazakii ATCC 29544, and Clostridium difficile ATCC 9689 had adhesion values ranging from 10 to 15%, and Listeria monocytogenes ATCC 15313 had the lowest adhesive value (3%). The ability of these bifidobacteria to inhibit pathogen adhesion and to displace pathogens previously adhering to mucus was also tested. The inhibition of pathogens adhesion by these bifidobacterial strains was variable and clearly strain dependent. In general, bifidobacterial strains of animal origin were better able to inhibit and displace pathogens than were human strains. Preliminary characterization of bacterial adhesion was accomplished using different pretreatments to explore adhesion mechanisms. The results indicate that different molecules are implicated in the adhesion of bifidobacteria to the human intestinal mucus, constituting a multifactorial process.     

Potential probiotic characteristics of Lactobacillus and Enterococcus strains isolated from traditional dadih fermented milk against pathogen intestinal colonization

Traditional fermented buffalo milk in Indonesia (dadih) has been believed to have a beneficial impact on human health, which could be related to the properties of the lactic acid bacteria (LAB) involved in its fermentation process. In previous studies, it was discovered that strains of dadih lactic isolates possessed some beneficial properties in vitro. In the present study, the adhesion capacity of specific LAB isolates from dadih to intestinal mucus was analyzed. Further, the ability to inhibit model human pathogens and displace them from mucus was assessed. The adhesion of tested LAB strains was strain-dependent and varied from 1.4 to 9.8%. The most adhesive Lactobacillus plantarum strain was IS-10506, with 9.8% adhesion. The competition assay between dadih LAB isolates and pathogens showed that a 2-h preincubation with L. plantarum at 37 degrees C significantly reduced pathogen adhesion to mucus. All tested LAB strains displaced and inhibited pathogen adhesion, but the results were strain-specific and dependent on time and pathogen strains. In general, L. plantarum IS-10506 showed the best ability against pathogen adhesion.     

Screening probiotics from Lactobacillus strains according to their abilities to inhibit pathogen adhesion and induction of pro-inflammatory cytokine IL-8

Probiotics can be screened according to their abilities to inhibit pathogen adhesion and inhibit the production of pro-inflammatory cytokines. Eleven Lactobacillus strains isolated from traditional fermented dairy foods in Xinjiang, China, were studied for their potential to inhibit adhesion of Escherichia coli to intestinal epithelial cells and to inhibit E. coli–induced production of interleukin (IL)-8 by intestinal epithelial cells. The results showed that the 11 strains could inhibit adhesion of E. coli to Caco-2 cell monolayers and inhibit the induction of IL-8 production by E. coli in HT-29 cells. The inhibiting activities of the Lactobacillus strains against E. coli adhesion and IL-8 induction were strain-specific and not positively correlated, whereas the excluding activity of the strains against E. coli adhesion and their coaggregation with E. coli were positively correlated. The effector molecules of the strains with probiotic potential should be identified to explain the mechanism behind these observations.     

Adhesive and chemokine stimulatory properties of potentially probiotic Lactobacillus strains

Five Lactobacillus plantarum strains and two Lactobacillus johnsonii strains, stemming either from African traditionally fermented milk products or children's feces, were investigated for probiotic properties in vitro. The relationship between the hydrophobic-hydrophilic cell surface and adhesion ability to HT29 intestinal epithelial cells was investigated, and results indicated that especially the L. johnsonii strains, which exhibited both hydrophobic and hydrophilic surface characteristics, adhered well to HT29 cells. Four L. plantarum and two L. johnsonii strains showed high adherence to HT29 cells, generally higher than that of the probiotic control strain Lactobacillus rhamnosus GG. Most strains with high adhesion ability also showed high autoaggregation ability. The two L. johnsonii strains coaggregated well with the intestinal pathogens Listeria monocytogenes Scott A, Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, and Salmonella enterica serovar Typhimurium ATCC 14028. The L. plantarum BFE 1685 and L. johnsonii 6128 strains furthermore inhibited the adhesion of at least two of these intestinal pathogens in coculture with HT29 cells in a strain-dependent way. These two potential probiotic strains also significantly increased interleukin-8 (IL-8) chemokine production by HT29 cells, although modulation of other cytokines, such as IL-1, IL-6, IL-10, monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor alpha (TNF-alpha), and transforming growth factor beta (TGF-beta), did not occur. Altogether, our results suggested that L. plantarum BFE 1685 and L. johnsonii BFE 6128 showed good adherence, coaggregated with pathogens, and stimulated chemokine production of intestinal epithelial cells, traits that may be considered promising for their development as probiotic strains.     

Assessment of adhesion properties of novel probiotic strains to human intestinal mucus

Potential new probiotic strains Lactobacillus brevis PELI, L. reuteri ING1, L. rhamnosus VTT E-800 and L. rhamnosus LC-705 were assessed for their adhesion properties using the human intestinal mucus model. The effect on the adhesion of exposure to acid and pepsin and to milk were tested to simulate gastric and food processing conditions, and the effect of different growth media on adhesion was tested. The properties of the four strains were compared to the well-investigated probiotic L. rhamnosus strain GG. Three of the tested strains showed significant adhesion properties in the mucus model, while L. brevis PELI had intermediate adhesion and L. rhamnosus LC-705 adhered poorly. Pretreatment with different milks decreased the adhesion and low pH and pepsin treatment reduced the adhesion of all tested strains except L. rhamnosus LC-705. No competitive exclusion of pathogenic Salmonella typhimurium or Escherichia coli SfaII was observed. The results indicate that major differences exist between tested proposed probiotic strains. The growth media and the food matrix significantly affect the adhesive ability of the tested strains. This has previously not been taken into account when selecting novel probiotic strains.     

Adhesion and competitive inhibition and displacement of human enteropathogens by selected lactobacilli

Competition with pathogens for adhesion and colonization of the mucosal surfaces are possible protective mechanisms of probiotics. Here, we assessed the adhesive properties and the ability to inhibit the adhesion and to displace pathogens of three selected Lactobacillus strains using Caco-2 cells and a human intestinal mucus model. The adhesion levels showed a great variability, ranging between 1% and 9.7% in the mucus model and between 7.7 and 61.1 bacterial cells/microscopy view in the Caco-2 model. A good correlation between both models was observed. The ability to inhibit the adhesion or to displace adhered pathogens was variable depending on both the lactobacilli and the pathogen tested. The inhibition and displacement profiles were very different suggesting that different mechanisms are implied in both processes. A very high specificity in the inhibition of the adhesion and displacement of enteropathogens by lactobacilli was observed indicating the need for a case-by-case assessment in order to select strains with the ability to inhibit or displace a specific pathogen.     

Adhesion of dairy propionibacteria to intestinal epithelial tissue in vitro and in vivo

Adhesion to the intestinal mucosa is a desirable property for probiotic microorganisms and has been related to many of their health benefits. In the present study, 24 dairy Propionibacterium strains were assessed with regard to their hydrophobic characteristics and their autoaggregation and hemagglutination abilities, since these traits have been shown to be indicative of adherence in other microorganisms. Six strains were further tested for their capacity to adhere to ileal epithelial cells in vitro and in vivo. The results of the study showed that propionibacteria were highly hydrophilic, and hemagglutination and autoaggregation were properties not commonly found among these microorganisms. No relationship was found between surface characteristics and adhesion ability, since hemagglutinating, autoaggregating, and nonautoaggregating bacteria were able to adhere to intestinal cells both in vitro and in vivo. Microscopic examination revealed that autoaggregating cells adhered in clusters, with adhesion being mediated by only a few bacteria, whereas the hemagglutinating and nonautoaggregating strains adhered individually or in small groups making contact with each epithelial cell with the entire bacterial surface. The in vitro assessment of adhesion was a good indication of the in vivo association of propionibacteria with the intestinal epithelium. Therefore, the in vitro method presented here should be valuable in screening routinely adhesive properties of propionibacteria for probiotic purposes. The adhesion ability of dairy propionibacteria would prolong their maintenance in the gut and increase the duration of their provision of beneficial effects in the host, supporting the potential of Propionibacterium in the development of new probiotic products.     

Adhesion properties and competitive pathogen exclusion ability of bifidobacteria with acquired acid resistance

The adhesion properties of Bifidobacterium longum and Bifidobacterium catenulatum strains with an acquired resistance to acid and their ability to competitively exclude Salmonella enterica serovar Typhimurium, Escherichia coli, Listeria monocytogenes, Enterobacter sakazakii, and Clostridium difficile from adhering to human intestinal mucus were evaluated and compared with the results when the same experiments were run with the original acid-sensitive strains. In half of the four studied cases, the acid-resistant derivative showed a greater ability to adhere to human intestinal mucus than the original strain. The ability of bifidobacteria to inhibit pathogen adhesion to mucus was not generally improved by the acquisition of acid resistance. In contrast, three of the four acid-resistant strains showed a greater ability to displace preadhered pathogens than the original strains, especially preadhered Salmonella Typhimurium and C. difficile. Overall, the induction of acid resistance in bifidobacteria could be a strategy when selecting strains with enhanced stability and improved surface properties that favor their potential functionality as probiotics against specific pathogens.     

Evaluation of Pediococcus pentosaceus strains isolated from Idly batter for probiotic properties in vitro

Idly batter is a traditional fermented food in South India and distribution of lactic acid bacteria (LAB) varies with season. Six bacteriocinogenic Pediococcus pentosaceus strains isolated from Idly batter were evaluated for probiotic properties in vitro. These isolates exhibited effective inhibition against various intestinal Gram positive and negative pathogens like Escherichia coli. These isolates especially, VJ13, VJ31 and VJ49 could tolerate 0.3% bile salt, gastric and intestinal conditions. All isolates exhibited strong auto-aggregation and co-aggregation (against Listeria monocytogenes and E. coli) with higher hydrophobicity and thus they could eliminate pathogen and prevent its adhesion to intestinal cells. All isolates except VJ41 assimilate cholesterol effectively, suggesting that they can lower the cholesterol, and because they produce β-galactosidase they can be used for lactose intolerance. Heat-killed P. pentosaceus VJ13 also assimilated cholesterol (19%) but not as effectively as live strains (73%). Among these isolates, VJ13 and VJ49, which exhibited efficient probiotic property, were evaluated for in vitro adhesion with Caco-2 cells. These isolates adhere more effectively with Caco-2 cells than the intestinal pathogen L. monocytogenes and prevent the pathogen adhesion to intestinal cells. Among these isolates, VJ13 has beneficial probiotic properties which can be exploited for formulation of functional foods.     

Probiotics and Its Functionally Valuable Products—A Review

During the past two decades probiotic bacteria have been increasingly proposed as health promoting bacteria in variety of food system, because of its safety, functional, and technological characteristics. Commonly, Lactobacillus spp., Bifidobacterium spp., Saccharomyces boulardii, and some other microorganisms have been considered as probiotic strains. Possibly these bacterial strains exerted several beneficial effects into gastrointestinal tract of host while administered with variety of food system. Lactic acid bacteria (LAB) usually produce antimicrobial substances like bacteriocin which have broad spectrum of antagonist effect against closely related Gram positive and Gram negative pathogens. LAB strains often produce polymeric substances such as exopolysaccharides (EPS) which increase the colonization of probiotic bacteria by cell–cell interactions in gastrointestinal tract. LAB also produces biosurfactant which showed that the wide range of antimicrobial activity against bacterial pathogen as well as its antiadhesive properties reduces the adhesion of pathogens into gastric wall membrane. Furthermore, LAB strains have also been reported for production of antioxidants which are ability to scavenge the free radicals such as superoxide anions and hydroxyl radicals. For this sense, this review article is mainly focused on the ecology, biosynthesis, genetics, target sites, and applications of bacteriocins and EPS from LAB strains. Moreover, this review discusses about the production and functions of nutritive essential element folate and iron chelating agent such as siderophores from LAB.     

Safety assessment of Lactobacillus strains: presence of putative risk factors in faecal, blood and probiotic isolates

The widespread use of immunosuppressive therapy and antimicrobial agents as well as novel probiotics without a long history of safe use has increased requirements for safety assessment of probiotic lactobacilli. In this study 44 faecal, 52 blood and 15 probiotic isolates (including 3 dairy strains) of Lactobacillus were assayed for their adhesion properties to extracellular matrix proteins and mucus, hemolysis, ability to avoid the induction of respiratory burst in peripheral blood mononucleocytes (PMN) and resistance to human serum. Among tested strains adhesion to collagen, fibrinogen and mucus was isolate-specific and no statistically significant differences were obtained between faecal, blood and probiotic isolates. However, blood isolates showed a trend for higher adhesion to mucus than probiotic strains (P=0.07). Probiotic strains induced lower respiratory burst in PMN when compared to the blood isolates (P<0.05). Moreover, there was a positive correlation between adhesion to collagen and induction of respiratory burst for faecal isolates (P<0.05). In the determination of serum resistance, probiotic strains showed a trend for lower sensitivity to human serum-mediated killing when compared to the faecal isolates (P=0.07). None of the measurable virulence factors were found to be present at statistically higher level in clinical blood isolates when compared to faecal and/or probiotic isolates indicating that these factors do not cause risk when safety of probiotics is considered. However, the significance of adhesion to mucus, low induction of respiratory burst in PMN and resistance to human serum-mediated killing may need further evaluation in experimental animal models and in epidemiological data.     

Protective action of Lactobacillus kefir carrying S-layer protein against Salmonella enterica serovar Enteritidis

Eight Lactobacillus kefir strains isolated from different kefir grains were tested for their ability to antagonize Salmonella enterica serovar Enteritidis (Salmonella enteritidis) interaction with epithelial cells. L. kefir surface properties such as autoaggregation and coaggregation with Salmonella and adhesion to Caco-2/TC-7 cells were evaluated. L. kefir strains showed significantly different adhesion capacities, six strains were able to autoaggregate and four strains coaggregated with Salmonella. Coincubation of Salmonella with coaggregating L. kefir strains significantly decreased its capacity to adhere to and to invade Caco-2/TC-7 cells. This was not observed with non coaggregating L. kefir strains. Spent culture supernatants of L. kefir contain significant amounts of S-layer proteins. Salmonella pretreated with spent culture supernatants (pH 4.5-4.7) from all tested L. kefir strains showed a significant decrease in association and invasion to Caco-2/TC-7 cells. Artificially acidified MRS containing lactic acid to a final concentration and pH equivalent to lactobacilli spent culture supernatants did not show any protective action. Pretreatment of this pathogen with spent culture supernatants reduced microvilli disorganization produced by Salmonella. In addition, Salmonella pretreated with S-layer proteins extracted from coaggregating and non coaggregating L. kefir strains were unable to invade Caco-2/TC-7 cells. After treatment, L. kefir S-layer protein was detected associated with Salmonella, suggesting a protective role of this protein on association and invasion.     

Assessment of potential probiotic properties of Lactobacillus spp., Lactococcus spp., and Pediococcus spp. strains isolated from kefir

In this study, the metabolic activities (in terms of quantities of the produced lactic acid, hydrogen peroxide, and exopolysaccharides) of 8 strains of Lactobacillus spp., Lactococcus spp., and Pediococcus spp., were determined. Lactic acid levels produced by strains were 8.1 to 17.4 mg/L. The L. acidophilus Z1L strain produced the maximum amount (3.18 μg/mL) of hydrogen peroxide. The exopolysaccharides (EPS) production by the strains was ranged between 173 and 378 mg/L. The susceptibility of 7 different antibiotics against these strains was also tested. All strains were found to be sensitive to ampicillin. The tolerance of the strains to low pH, their resistance to bile salts of strains, and their abilities to autoaggregate and coaggregate with Escherichia coli ATCC 11229 were also evaluated. High EPS-producing strains showed significant autoaggregation and coaggregation ability with test bacteria (P < 0.01). A correlation also was determined between EPS production and acid-bile tolerance (P < 0.05). EPS production possibly affects or is involved in acid-bile tolerance and aggregation of Lactobacillus spp., Lactococcus spp., and Pediococcus spp. strains and supports the potential of L. acidophilus Z1L strain as new probiotic.     

婴儿源益生性双歧杆菌的筛选及肠道定殖性研究

本研究旨在从婴儿粪便中筛选出具有潜在益生特性的双歧杆菌,并探究其肠道定殖情况,为双歧杆菌的产品开发提供优良的菌株。采用MRS培养基对样品进行分离纯化,菌株经F6PPK检测及16S r DNA测序鉴定,之后进行模拟胃肠液、胆盐耐受性、对食源性致病菌(大肠杆菌、沙门氏菌、单增李斯特菌等)的抑制及对HT-29细胞的粘附能力测定,将筛选出的菌株进行动物实验,测定其肠道定殖能力。分离到的27株双歧杆菌,经分子生物学鉴定为7个不同的种:Bifidobacterium longum、Bifidobacterium breve、Bifidobacterium bifidum、Bifidobacterium pseudocatenulatum、Bifidobacterium infantis、Bifidobacterium animalis和Bifidobacterium adolescentis。体外实验表明,B.longum A9、B.breve A4、B.bifidum B6、B.longum C6、B.adolescentis F8和B.infantis H6等具有较强的潜在益生特性;动物实验表明,B.infantis H6和B.longum C6具有较强的肠道定殖能力。B.longum C6和B.infantis H6有望作为优良的益生性菌株,应用于双歧杆菌的产品开发。