An In Vitro Study on Bacterial Growth Interactions and Intestinal Epithelial Cell Adhesion Characteristics of Probiotic Combinations

Techno-functional characterization of fecal lactobacilli isolates of Bos indicus calves for probiotic properties

In this study, 105 bacterial colonies were isolated from the feces of newborn healthy Bos indicus calves and 37 isolates were confirmed using morphological, biochemical tests, and genus-specific PCR as lactobacilli. 11 isolates were then short-listed for in vitro probiotic testing based on their ability to dwell under acid and bile stress. Species-level identification using 16S rRNA gene sequencing revealed that they were Ligilactobacillus salivarius. These isolates flourished in 0.4% phenol, depicting resistance in adverse conditions encountered in the gastrointestinal tract. The results of cell surface hydrophobicity were found to be 74.50% for RBL12 and 62.62% for RBL09 in hexadecane and xylene, respectively, and that of auto-aggregation was highest in RBL26 (58.92%). These isolates also produced digestive enzymes like amylase, protease, and β-galactosidase. Further assays reiterated their antimicrobial and coaggregation potential against diarrhea-causing pathogens like Escherichia coli ATCC-25922 and Salmonella arizonae ATCC-13314. Biosafety assessment revealed that none of the tested isolates were hemolytic and mucinolytic in nature. Furthermore, the antioxidant potential of the isolates was also confirmed using 1,1‑diphenyl‑2‑picrylhydrazyl (DPPH) and ferric ion-reducing antioxidant power (FRAP) assay. Along with efficient utilization of inulin, isolates showed promising adhesion ability to the HT-29 cell line. The current findings hence conclude that these Lactobacillus isolates can be exploited as animal probiotics for potential application in young calves to foster gut health and immunity.

Viability and In Vitro Gastrointestinal Transit Tolerance of Multispecies Probiotic Combinations Incorporated into Orange Juice and Drinking Water

Little is known about how combining probiotics affects the storage survival and functional performance of individual probiotics when incorporated into non-dairy drinks. Viability of Lacticaseibacillus rhamnosus GG (LG), Limosilactobacillus reuteri ATCC 55730 (LR), Bifidobacterium animalis subsp. lactis BB-12 (Bb), and Propionibacterium jensenii 702 (PJ), either alone or in multi-species combinations included in orange juice (OJ), were assessed during storage in refrigerated conditions and compared with bottled water (BW). The tolerance of probiotics included in refrigerated OJ to simulated gastrointestinal conditions was also examined. LG and LR viabilities were significantly higher in OJ than in BW (p ≤ 0.001), while the reverse was evident for PJ. Bb maintained high viability in both drinks. LG-PJ in both drinks and Bb-PJ in BW resulted in greater viabilities among the paired combinations compared to their respective monocultures when incorporated separately (p ≤ 0.001). The viability of LG in the LG-Bb-PJ combination improved significantly in BW compared with LG alone (p ≤ 0.001). OJ did not alter bacterial tolerance to simulated gastric juice but diminished tolerance to simulated intestinal juice (SIJ). In all combinations, tolerance of LG and LR to SIJ was improved, whereas tolerance of PJ declined significantly compared with respective monocultures (p ≤ 0.001). In conclusion, probiotic storage stability and gastrointestinal transit tolerance were species-dependent and affected by carrier type and combinations. These effects should be considered when formulating probiotic products.

Maternal probiotic intake attenuates ileal Crh receptor gene expression in maternally separated rat offspring

Corticotropin-releasing hormone (Crh) and its receptors (Crhr) mediate stress-induced gastrointestinal dysfunctions. Neonatal maternal separation (MS) increased ileal Crhr1 transcript quantities in young rat offspring. Exposure to either MS or adulthood restraint stress increased ileal Crhr1 and Crhr2 transcript quantities only in adult female offspring. Maternal probiotic intervention reversed Crhr overexpression, suggesting a potential early prophylaxis against stress-induced gut dysfunctions.

Limosilactobacillus reuteri Regulating Intestinal Function: A Review

Probiotics have extensive use in daily life, due to the function of the changing intestinal metabolism and material conversion processes, wherein they remodel the intestinal microbiota, regulate the intestinal function and affect the organism’s health. Limosilactobacillus reuteri (L. reuteri), originally discovered in breast milk and currently reported to be present within the gut of almost all vertebrates and mammals, is an intestinal probiotic with prebiotic efficacy. Most L. reuteri have good intestinal colonization and bacteriocin secretion abilities, which can increase the expression of the mucin (mucoprotein) genes 2 MUC2 and MUC13, which in turn promote the development and maturation of intestinal organoids, and augment mucin secretion. In enteritis patients, L. reuteri downregulates α Tumor necrosis factor-α, (TNF-α), Interleukin-6 (IL-6), IL-8, and IL-12 expression to attenuate inflammation. It also induces the host’s production of immunoglobulin A (IGA), which manipulates the intestinal microbial community, inhibiting the growth of pathogens. L. reuteri has been widely used in daily life. with in-depth studies having been conducted on the prebiotic effects of L. reuteri. However, the complexity of its application in a clinical setting is still unclear because the pathogenesis of various diseases still requires a large amount of data and theoretical support.

In vitro Evaluation of Antibacterial, Cytotoxic and Adherence Studies of Selected Commercial Probiotics

There is increasing scientific evidence and commercial interest for using probiotics for eliminating and handling of specific diseases. Probiotics can be evaluated for its role and performance against isolated pathogens from contaminating sources. The present work reports on invitro antimicrobial activity of commercial selected probiotics against pathogenic microbe Vibrio parahaemolyticus. The work also describes cytotoxic activities using MTT assay and adherence studies of selected probiotics. Results for the studies showed maximum zone of inhibition 13.66±0.46mm in probiotic enteroplus,12.33±0.93mm in lactobacillus (NCIM2056) and 10.66±0.93mm in Avant Bact. Cytotoxicity was expressed as IC50(µg/ml) values, observed on CaCO cell lines for different probiotics. Avant Bact showed a IC50 value of 104.7745, Lactobacillus (NCIM2056) a value of 58.13223 and Enteroplus a value of 50.09716. These values expressed different safety aspects of probiotics used for study. Finally the adherence study was done to check probiotic colonizing capacity. The probiotics showed varied adherence capacity against caco cell lines. Enteroplus has % adhesion of 10.25±0.74, Avant Bact. 7.25±0.82 and Lactobacillus (NCIM2056) 7.5±1.12. In conclusion antimicrobial results show importance of probiotics to be used against specific gastro intestinal diseases. Cytotoxicity determines safety aspects of probiotics and adherence study determines probiotic as a promising candidate for in vivo studies.

Barrier Protection and Recovery Effects of Gut Commensal Bacteria on Differentiated Intestinal Epithelial Cells In Vitro

Alterations in the gut microbiota composition play a crucial role in the pathogenesis of inflammatory bowel disease (IBD) as specific commensal bacterial species are underrepresented in the microbiota of IBD patients. In this study, we examined the therapeutic potential of three commensal bacterial species, Faecalibacterium prausnitzii (F. prausnitzii), Roseburia intestinalis (R. intestinalis) and Bacteroides faecis (B. faecis) in an in vitro model of intestinal inflammation, by using differentiated Caco-2 and HT29-MTX cells, stimulated with a pro-inflammatory cocktail consisting of interleukin-1β (IL-1β), tumor necrosis factor-α (TNFα), interferon-γ (IFNγ), and lipopolysaccharide (LPS). Results obtained in this work demonstrated that all three bacterial species are able to recover the impairment of the epithelial barrier function induced by the inflammatory stimulus, as determined by an amelioration of the transepithelial electrical resistance (TEER) and the paracellular permeability of the cell monolayer. Moreover, inflammatory stimulus increased claudin-2 expression and decreased occludin expression were improved in the cells treated with commensal bacteria. Furthermore, the commensals were able to counteract the increased release of interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) induced by the inflammatory stimulus. These findings indicated that F. prausnitzii, R. intestinalis and B. faecis improve the epithelial barrier integrity and limit inflammatory responses.

In vitro assessment of Enterococcus faecalis MTC 1032 as the potential probiotic in food supplements

Probiotics become important bacteria in our daily life due to their benefit on human health. In this study, a subset of bacterial strains from children was isolated and evaluated for beneficial probiotic traits such as antimicrobial activity, bile and acid tolerance, and pathogenic cell adherence inhibition. The strain with the best antimicrobial activity was selected for further characterization on the basis of morphological, biochemical characteristics and gene sequence. This strain was Gram-positive, oxidase and catalase-negative, and it produced acids by fermenting sugar and starch as carbon sources. Additionally, it could only hydrolyze bile-esculin, but not red blood cells. The 16S rDNA gene sequence revealed that this strain was Enterococcus faecalis. Interestingly, this strain effectively inhibited a variety of pathogens by acid and bacteriocin production and was bile-tolerant, able to survive under acidic condition. In the safety assessments, E. faecalis MTC 1032 could adhere to host epithelial cells and evidently inhibited pathogenic cell adhesion as demonstrated by cell reduction over time of E. coli ATCC 25922 and S. typhimurium ATCC 13311 on Caco-2 cell line. In summary, it was clearly represented that E. faecalis MTC 1032 provided suitable properties and could be a candidate as a probiotic strain in food supplements.

Organ-on-a-Chip Technology for Reproducing Multiorgan Physiology

In the drug development process, the accurate prediction of drug efficacy and toxicity is important in order to reduce the cost, labor, and effort involved. For this purpose, conventional 2D cell culture models are used in the early phase of drug development. However, the differences between the in vitro and the in vivo systems have caused the failure of drugs in the later phase of the drug-development process. Therefore, there is a need for a novel in vitro model system that can provide accurate information for evaluating the drug efficacy and toxicity through a closer recapitulation of the in vivo system. Recently, the idea of using microtechnology for mimicking the microscale tissue environment has become widespread, leading to the development of "organ-on-a-chip." Furthermore, the system is further developed for realizing a multiorgan model for mimicking interactions between multiple organs. These advancements are still ongoing and are aimed at ultimately developing "body-on-a-chip" or "human-on-a-chip" devices for predicting the response of the whole body. This review summarizes recently developed organ-on-a-chip technologies, and their applications for reproducing multiorgan functions.

Adherence potential of indigenous lactic acid bacterial isolates obtained from fermented foods of Western Himalayas to intestinal epithelial Caco-2 and HT-29 cell lines

The adherence of bacteria to epithelial cells and mucosal surfaces is a prerequisite for their colonization in the gut and a key criterion for the selection of probiotics. In this study, the eleven indigenous lactic acid bacterial isolates obtained from traditional fermented foods of Western Himalayas were screened for their adherence potential to intestinal epithelial cell lines. The level of adherence of eleven indigenous isolates to Caco-2 and HT-29 cell lines varied from 2.45 ± 0.5 to 9.55 ± 0.76% and 4.11 ± 0.68 to 12.88 ± 0.63%, respectively. Percent adhesion of indigenous isolates to Caco-2 cells was relatively lower as compared to HT-29 cells. Indigenous isolate AdF10 (L. plantarum) was found to be the most adhesive to HT-29 and Caco-2 with corresponding figures of 12.88 ± 0.63 and 9.55 ± 0.76%, respectively. AdF4 (B. coagulans) was found to be least adhesive to HT-29 and Caco-2 with respective corresponding figures of 4.11 ± 0.68 and 2.45 ± 0.5%. Based on the percent adhesion values, indigenous isolate AdF10 (L. plantarum) was comparable to the reference probiotic strain L. rhamnosus GG-ATCC-53103 with respective adhesion of 13.5 ± 1.19 and 10.33 ± 0.64% to HT-29 and Caco-2 cell lines. It was closely followed by indigenous isolates AdF5 (L. plantarum) and AdF6 (L. plantarum); thus, indicating their potential as a promising probiotic candidates.

Short communication: A study of Lactobacillus isolates' adherence to and influence on membrane integrity of human Caco-2 cells

The selection criteria of ideal probiotic bacteria are complex and involve many factors. One key criterion is based on the ability of the probiotic bacteria to adhere to the epithelial lining of the gastrointestinal tract. The objective of this study was to evaluate and compare the adherence and influence on membrane integrity of 2 selected lactobacilli isolates-Lactobacillus rhamnosus MI13 (dairy food origin) and L. plantarum RC2 (bovine rumen origin)-to Caco-2 cells in the presence and absence of Escherichia coli. The adhesion and influence on membrane integrity properties of the 2 Lactobacillus isolates were compared with Escherichia coli, a human commensal bacterium. From the adhesion studies, we concluded that the bovine rumen isolate exhibited better adherence to Caco-2 cells than the dairy food isolate. In contrast, the dairy food isolate better protected the Caco-2 monolayer from damage induced by ethanol.

Propionibacterium freudenreichii Surface Protein SlpB Is Involved in Adhesion to Intestinal HT-29 Cells

Propionibacterium freudenreichii is a beneficial bacterium traditionally used as a cheese ripening starter and more recently for its probiotic abilities based on the release of beneficial metabolites. In addition to these metabolites (short-chain fatty acids, vitamins, and bifidogenic factor), P. freudenreichii revealed an immunomodulatory effect confirmed in vivo by the ability to protect mice from induced acute colitis. This effect is, however, highly strain-dependent. Local action of metabolites and of immunomodulatory molecules is favored by the ability of probiotics to adhere to the host cells. This property depends on key surface compounds, still poorly characterized in propionibacteria. In the present study, we showed different adhesion rates to cultured human intestinal cells, among strains of P. freudenreichii. The most adhesive one was P. freudenreichii CIRM-BIA 129, which is known to expose surface-layer proteins. We evidenced here the involvement of these proteins in adhesion to cultured human colon cells. We then aimed at deciphering the mechanisms involved in adhesion. Adhesion was inhibited by antibodies raised against SlpB, one of the surface-layer proteins in P. freudenreichii CIRM-BIA 129. Inactivation of the corresponding gene suppressed adhesion, further evidencing the key role of slpB product in cell adhesion. This work confirms the various functions fulfilled by surface-layer proteins, including probiotic/host interactions. It opens new perspectives for the understanding of probiotic determinants in propionibacteria, and for the selection of the most efficient strains within the P. freudenreichii species.

Challenges in simulating the human gut for understanding the role of the microbiota in obesity

There is an elevated incidence of cases of obesity worldwide. Therefore, the development of strategies to tackle this condition is of vital importance. This review focuses on the necessity of optimising in vitro systems to model human colonic fermentation in obese subjects. This may allow to increase the resolution and the physiological relevance of the information obtained from this type of studies when evaluating the potential role that the human gut microbiota plays in obesity. In light of the parameters that are currently used for the in vitro simulation of the human gut (which are mostly based on information derived from healthy subjects) and the possible difference with an obese condition, we propose to revise and improve specific standard operating procedures.

Production and Biomedical Applications of Probiotic Biosurfactants

Biosurfactants have been widely used for environmental and industrial applications. However, their use in medical field is still limited. Probiotic biosurfactants possess an immense antimicrobial, anti-adhesive, antitumor, and antibiofilm potential. Moreover, they have an additional advantage over conventional microbial surfactants because probiotics are an integral part of normal human microflora and their biosurfactants are innocuous to human. So, they can be effectively exploited for medicinal use. Present review is aimed to discourse the production and biomedical applications of probiotic biosurfactants.

Perinatal maternal probiotic intervention impacts immune responses and ileal mucin gene expression in a rat model of irritable bowel syndrome

Alterations in immune responses and intestinal secretory state are among features commonly observed in the maternal separation (MS) rat model of Irritable Bowel Syndrome. This study examined whether perinatal maternal introduction of probiotics influences plasma immune markers and ileal mucin-2 (MUC2) gene expression in rat offspring exposed to neonatal maternal separation (MS, 3 h/day, postnatal days (PND) 2-14) and/or subsequently to acute restraint stress in adulthood (AS, 30 min/day, PND 83-85). Data analysis indicated that stress protocols did not affect plasma tumour necrosis factor alpha (TNF-α), interferon gamma (IFN-γ) and interleukin (IL)-6 levels in young offspring (PND 24) born to the vehicle-treated dams. Maternal probiotic intervention was associated with significantly decreased IFN-γ levels in young offspring compared with non-probiotic offspring (P≤0.05). It also induced a significant increase in IL-6 levels in MS pups (P≤0.05). Exposure of both non-MS and MS offspring to AS induced a significant increase in haptoglobin levels compared to controls (P≤0.05), whereas all offspring born to the probiotic-treated dams, irrespective of stress treatment conditions, exhibited significantly decreased haptoglobin levels to well below the control levels (P≤0.05). MS and/or AS did not affect ileal expression of MUC2 in offspring born to the non-probiotic treated dams. While maternal probiotic intake significantly downregulated ileal gene expression of MUC2 in MS male young offspring, it was associated with significantly upregulated MUC2 mRNA expression in MS or AS adult male offspring. These findings suggest that maternal probiotic intervention may exert long-lasting anti-inflammatory effects and impact gut outcomes in offspring at increased risk of dysfunctional gut.

Lactobacillus reuteri DSM 17938 differentially modulates effector memory T cells and Foxp3+ regulatory T cells in a mouse model of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is an inflammatory disease with evidence of increased production of proinflammatory cytokines in the intestinal mucosa. Lactobacillus reuteri DSM 17938 (LR17938) has been shown to have anti-inflammatory activities in an experimental model of NEC. Activated effector lymphocyte recruitment to sites of inflammation requires the sequential engagement of adhesion molecules such as CD44. The phenotype of CD44(+)CD45RB(lo) separates T effector/memory (Tem) cells from naive (CD44(-)CD45RB(hi)) cells. It is unknown whether these Tem cells participate in the inflammation associated with NEC and can be altered by LR17938. NEC was induced in 8- to 10-day-old C57BL/6J mice by gavage feeding with formula and exposure to hypoxia and cold stress for 4 days. Survival curves and histological scores were analyzed. Lymphocytes isolated from mesenteric lymph nodes and ileum were labeled for CD4, CD44, CD45RB, intracellular Foxp3, and Helios and subsequently analyzed by flow cytometry. LR17938 decreased mortality and the incidence and severity of NEC. The percentage of Tem cells in the ileum and mesenteric lymph nodes was increased in NEC but decreased by LR17938. Conversely, the percentage of CD4(+)Foxp3(+) regulatory T (Treg) cells in the intestine decreased during NEC and was restored to normal by LR17938. The majority of the Treg cells preserved by LR17938 were Helios+ subsets, possibly of thymic origin. In conclusion, LR17938 may represent a useful treatment to prevent NEC. The mechanism of protection by LR17938 involves modulation of the balance between Tem and Treg cells. These T cell subsets might be potential biomarkers and therapeutic targets during intestinal inflammation.

3-D intestinal scaffolds for evaluating the therapeutic potential of probiotics

Biomimetic in vitro intestinal models are becoming useful tools for studying host-microbial interactions. In the past, these models have typically been limited to simple cultures on 2-D scaffolds or Transwell inserts, but it is widely understood that epithelial cells cultured in 3-D environments exhibit different phenotypes that are more reflective of native tissue, and that different microbial species will preferentially adhere to select locations along the intestinal villi. We used a synthetic 3-D tissue scaffold with villous features that could support the coculture of epithelial cell types with select bacterial populations. Our end goal was to establish microbial niches along the crypt-villus axis in order to mimic the natural microenvironment of the small intestine, which could potentially provide new insights into microbe-induced intestinal disorders, as well as enabling targeted probiotic therapies. We recreated the surface topography of the small intestine by fabricating a biodegradable and biocompatible villous scaffold using poly lactic-glycolic acid to enable the culture of Caco-2 with differentiation along the crypt-villus axis in a similar manner to native intestines. This was then used as a platform to mimic the adhesion and invasion profiles of both Salmonella and Pseudomonas, and assess the therapeutic potential of Lactobacillus and commensal Escherichia coli in a 3-D setting. We found that, in a 3-D environment, Lactobacillus is more successful at displacing pathogens, whereas Nissle is more effective at inhibiting pathogen adhesion.

A novel flotation technique for the separation of nonadherent micro-organisms from a substrate

An understanding of adherence ability is crucial in many areas, for example, in research on biofilms, evaluation of probiotics or in biotechnology. In all these analyses, the reproducible washing is very important in the prevention of false results. During washing, the force, direction of the flow, position of the pipette tip, number of washing cycles, type of washing solution and the way of removing the washing solution can be sources of inappropriate stress to attached cells. To overcome these problems, we here propose the use of high mass density solutions as flotation agents. As the density of bacteria is lower than that of the flotation solutions, nonattached or weakly attached bacteria are moved to the surface due to hydrostatic force. Caesium chloride, ammonium nitrate and sodium diatrizoate solutions, which are commonly used as FAs, were compared with a standard method of rinsing. Several concentrations of agents were used to investigate the optimal concentration and influence of hydrostatic pressure on adhered micro-organisms. We show that flotation is a rapid method for distinguishing between adhered and weakly attached or loosed cells with reproducible results. Due to its range of possible mass density concentration, the best FA was shown to be caesium chloride.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first study that suggests using flotation agents to separate planktonic from adhered bacteria. When a high-density solution is used, buoyancy of bacteria ensures their segregation in the solution. Flotation agents could be used instead of washing procedure, which is inaccurate and hardly reproducible. High-density flotation agents could be used for more precise evaluation of bacterial adherence in many assays, such as research of biofilms or evaluation of probiotics.

Evaluation of adhesion properties and antibacterial activities of the infant gut commensal Bifidobacterium bifidum PRL2010

Bifidobacteria are extensively exploited by the food industry as health-promoting microorganisms. However, very little is known about the molecular mechanisms responsible for these beneficial activities, or the molecular players that sustain their ability to colonize and persist within the human gut. Here, we have investigated the enteric adaptation features of the gut commensal Bifidobacterium bifidum PRL2010, originally isolated from infant feces. This strain was able to survive under gastrointestinal challenges, while it was shown to adhere to human epithelial intestinal cell monolayers (Caco 2 and HT-29), thereby inhibiting adhesion of pathogenic bacteria such as Escherichia coli and Cronobacter sakazakii.

Lactobacillus reuteri influences regrowth of mutans streptococci after full-mouth disinfection: a double-blind, randomised controlled trial

This study assessed whether the persistence of Lactobacillus reuteri DSM 17938 and ATCC PTA 5289 in saliva could delay the regrowth of mutans streptococci (MS) after a full-mouth disinfection with chlorhexidine (CHX). A randomised, double-blind, placebo-controlled study with a 6-week intervention period and 3- and 6-month follow-up was performed. 62 healthy subjects with moderate to high counts of MS were randomly assigned to a test group (n = 32) or a placebo group (n = 30). Before onset of the intervention, subjects received two sessions of professional cleaning, flossing, and application of CHX varnish and rinsed their mouth with a CHX solution between the sessions (2 days). Thereafter, the test group used probiotic lozenges (2/day) containing L. reuteri (DSM 17938 and ATCC PTA 5289; 1 × 10(8) CFU of each strain), and the placebo group used identical lozenges lacking the lactobacilli. Saliva samples were collected and cultured onto selective media, and isolates of L. reuteri as well as DNA directly extracted from saliva were tested by polymerase chain reaction (PCR) with specific primers. Presence of salivary MS was analysed with a chair-side test. L. reuteri was frequently detected by culture during the intervention period but in only 3 test group subjects at follow-ups. Regrowth of MS statistically significantly differed depending on the presence or absence of L. reuteri DSM 17938 detected by PCR. We conclude that cultivable L. reuteri strains may only sporadically be confirmed after termination of the intervention, but subjects with PCR-detected L. reuteri demonstrated slower regrowth of MS.

Effect of maternal probiotic intervention on HPA axis, immunity and gut microbiota in a rat model of irritable bowel syndrome

OBJECTIVE

To examine whether maternal probiotic intervention influences the alterations in the brain-immune-gut axis induced by neonatal maternal separation (MS) and/or restraint stress in adulthood (AS) in Wistar rats.

DESIGN

Dams had free access to drinking water supplemented with Bifidobacterium animalis subsp lactis BB-12® (3 × 10(9) CFU/mL) and Propionibacterium jensenii 702 (8.0 × 10(8) CFU/mL) from 10 days before conception until postnatal day (PND) 22 (weaning day), or to control ad lib water. Offspring were subjected to MS from PND 2 to 14 or left undisturbed. From PND 83 to 85, animals underwent 30 min/day AS, or were left undisturbed as controls. On PND 24 and 86, blood samples were collected for corticosterone, ACTH and IgA measurement. Colonic contents were analysed for the composition of microflora and luminal IgA levels.

RESULTS

Exposure to MS significantly increased ACTH levels and neonatal fecal counts of aerobic and anaerobic bacteria, E. coli, enterococci and clostridia, but reduced plasma IgA levels compared with non-MS animals. Animals exposed to AS exhibited significantly increased ACTH and corticosterone levels, decreased aerobic bacteria and bifidobacteria, and increased Bacteroides and E. coli counts compared to non-AS animals. MS coupled with AS induced significantly decreased anaerobes and clostridia compared with the non-stress adult controls. Maternal probiotic intervention significantly increased neonatal corticosterone levels which persisted until at least week 12 in females only, and also resulted in elevated adult ACTH levels and altered neonatal microflora comparable to that of MS. However, it improved plasma IgA responses, increased enterococci and clostridia in MS adults, increased luminal IgA levels, and restored anaerobes, bifidobacteria and E. coli to normal in adults.

CONCLUSION

Maternal probiotic intervention induced activation of neonatal stress pathways and an imbalance in gut microflora. Importantly however, it improved the immune environment of stressed animals and protected, in part, against stress-induced disturbances in adult gut microflora.

Multifaceted attributes of dairy propionibacteria: a review

Dairy propionibacteria are Generally Recognized as Safe (GRAS) status microorganisms which have been traditionally used for the manufacture of Swiss type cheeses. In the last two decades various added features and functionalities have been discovered and developed from these bacteria. Propionibacteria are robust organisms with remarkable adaptability to technological and physiological stress conditions. Besides, they also display a multitude of health promoting properties like modulation of gut microbiota, improved gut physiology and immunomodulation suggesting their promising probiotic potential. Propionibacteria produce an interestingly wide range of functional biomolecules like B group vitamins, trehalose, conjugated linoleic acid, propionic acid, bacteriocins, bifidogenic factors etc. These bacteria are thus now being explored for designing novel functional foods as well as for industrial production of nutraceuticals. Growing interest in these bacteria is fueled by the first whole genome sequencing of a Propionibacterium freudenreichii strain providing a platform for better understanding of various pathways and further improvement in related process technologies.

Assessing the adhesion of putative indigenous probiotic lactobacilli to human colonic epithelial cells

BACKGROUND & OBJECTIVES

Adherence of bacteria to epithelial cells and mucosal surfaces is a key criterion for selection of probiotic. We assessed the adhesion property of selected indigenous probiotic Lactobacillus strains based on their hydrophobicity and ability to adhere to human epithelial cells.

METHODS

Five human faecal Lactobacillus isolates, one from buffalo milk and one from cheese were assessed for hydrophobicity following the microbial adhesion to hydrocarbons (MATH) method and colonization potentials based on their adherence to Caco2 and HT-29 colonic adenocarcinomal human intestinal epithelial cell lines. Lactobacillus strains that adhered to Caco2 and HT-29 cell lines were quantified by plating after trypsinization and simultaneously the adhered bacteria were also examined microscopically after staining with Geimsa stain and counted in different fields.

RESULTS

Among the tested faecal isolates, L. plantarum Lp91 showed maximum percentage hydrophobicity (35.73±0.40 for n-hexadecane and 34.26±0.63 for toluene) closely followed by L. plantarum Lp9 (35.53±0.29 for n-hexadecane and 33.00±0.57 for toluene). Based on direct adhesion to epithelial cells, L. plantarum Lp91 was the most adhesive strain to HT-29 and Caco2 cell lines with per cent adhesion values of 12.8 ± 1.56 and 10.2 ± 1.09, respectively. L. delbrukeii CH4, was the least adhesive with corresponding figures of 2.5 ± 0.37 and 2.6 ± 0.20 per cent on HT-29 and Caco2 cell lines. Adhesion of the six isolated Lactobacillus strain to HT-29 cell and Caco2 lines as recorded under microscope varied between 131.0 ± 13.9 (Lp75) to 342.7 ± 50.52 (Lp91) and 44.7 ± 9.29 (CH4) to 315.7± 35.4 (Lp91), respectively.

INTERPRETATION & CONCLUSIONS

Two Indigenous probiotic Lactobacillus strains (Lp9, Lp91) demonstrated their ability to adhere to epithelial cell and exhibited strong hydrophobicity under in vitro conditions, and thus could have better prospects to colonize the gut with extended transit.

Human gut-on-a-chip inhabited by microbial flora that experiences intestinal peristalsis-like motions and flow

Development of an in vitro living cell-based model of the intestine that mimics the mechanical, structural, absorptive, transport and pathophysiological properties of the human gut along with its crucial microbial symbionts could accelerate pharmaceutical development, and potentially replace animal testing. Here, we describe a biomimetic 'human gut-on-a-chip' microdevice composed of two microfluidic channels separated by a porous flexible membrane coated with extracellular matrix (ECM) and lined by human intestinal epithelial (Caco-2) cells that mimics the complex structure and physiology of living intestine. The gut microenvironment is recreated by flowing fluid at a low rate (30 μL h(-1)) producing low shear stress (0.02 dyne cm(-2)) over the microchannels, and by exerting cyclic strain (10%; 0.15 Hz) that mimics physiological peristaltic motions. Under these conditions, a columnar epithelium develops that polarizes rapidly, spontaneously grows into folds that recapitulate the structure of intestinal villi, and forms a high integrity barrier to small molecules that better mimics whole intestine than cells in cultured in static Transwell models. In addition, a normal intestinal microbe (Lactobacillus rhamnosus GG) can be successfully co-cultured for extended periods (>1 week) on the luminal surface of the cultured epithelium without compromising epithelial cell viability, and this actually improves barrier function as previously observed in humans. Thus, this gut-on-a-chip recapitulates multiple dynamic physical and functional features of human intestine that are critical for its function within a controlled microfluidic environment that is amenable for transport, absorption, and toxicity studies, and hence it should have great value for drug testing as well as development of novel intestinal disease models.

Influence of adhesion and bacteriocin production by Lactobacillus salivarius on the intestinal epithelial cell transcriptional response

Lactobacillus salivarius strain UCC118 is a human intestinal isolate that has been extensively studied for its potential probiotic effects in human and animal models. The objective of this study was to determine the effect of L. salivarius UCC118 on gene expression responses in the Caco-2 cell line to improve understanding of how the strain might modulate intestinal epithelial cell phenotypes. Exposure of Caco-2 cells to UCC118 led to the induction of several human genes (TNFAIP3, NFKBIA, and BIRC3) that are negative regulators of inflammatory signaling pathways. Induction of chemokines (CCL20, CXCL-1, and CXCL-2) with antimicrobial functions was also observed. Disruption of the UCC118 sortase gene srtA causes reduced bacterial adhesion to epithelial cells. Transcription of three mucin genes was reduced significantly when Caco-2 cells were stimulated with the ΔsrtA derivative of UCC118 compared to cells stimulated with the wild type, but there was no significant change in the transcription levels of the anti-inflammatory genes. UCC118 genes that were significantly upregulated upon exposure to Caco-2 cells were identified by bacterial genome microarray and consisted primarily of two groups of genes connected with purine metabolism and the operon for synthesis of the Abp118 bacteriocin. Following incubation with Caco-2 cells, the bacteriocin synthesis genes were transcribed at higher levels in the wild type than in the ΔsrtA derivative. These data indicate that L. salivarius UCC118 influences epithelial cells both through modulation of the inflammatory response and by modulation of intestinal cell mucin production. Sortase-anchored cell surface proteins of L. salivarius UCC118 have a central role in promoting the interaction between the bacterium and epithelial cells.