Role of commercial probiotic strains against human pathogen adhesion to intestinal mucus

Latilactobacillus curvatus: A Candidate Probiotic with Excellent Fermentation Properties and Health Benefits

Latilactobacillus curvatus is a candidate probiotic that has been included in the list of recommended biological agents for certification by the European Food Safety Authority. According to the published genomic information, L. curvatus has several genes that encode metabolic pathways of carbohydrate utilization. In addition, there are some differences in cell surface complex related genes of L. curvatus from different sources. L. curvatus also has several genes that encode bacteriocin production, which can produce Curvacin A and Sakacin P. Due to its ability to produce bacteriocin, it is often used as a bioprotective agent in fermented meat products, to inhibit the growth of a variety of pathogenic and spoilage bacteria. L. curvatus exerts some probiotic effects, such as mediating the production of IL-10 by dendritic cells through NF-κB and extracellular regulated protein kinases (ERK) signals to relieve colitis in mice. This review is the first summary of the genomic and biological characteristics of L. curvatus. Our knowledge on its role in the food industry and human health is also discussed, with the aim of providing a theoretical basis for the development of applications of L. curvatus.

Probiotic Potential of Lactic Acid Starter Cultures Isolated from a Traditional Fermented Sorghum-Millet Beverage

The purpose of this study was to establish the probiotic potential of lactic acid bacteria (LAB) starter cultures, Lb. plantarum MNC 21, L. lactis MNC 24, and W. confusa MNC 20, isolated from a traditionally fermented sorghum-millet beverage from Uganda. The cultures were examined for tolerance to acid and bile salts, bile salt hydrolase (BSH) activity, antibiotic susceptibility, biogenic amine production, mucin degradation, hydrophobicity, auto-aggregation, adherence to the ileum, coaggregation, and antimicrobial properties against selected pathogenic species. Lb. rhamnosus yoba 2012, a known probiotic, was the reference. The isolates were tolerant to acid (pH = 3) and bile (1%). W. confusa MNC 20 and Lb. plantarum MNC 21 exhibited medium BSH activity (11-15 mm diameter of hydrolysis zone) while L. lactis and Lb. rhamnosus yoba 2012 exhibited low BSH activity (<10 mm diameter of hydrolysis zone). All isolates lacked mucolytic activity. Lb. plantarum MNC 21 and W. confusa MNC 20 produced agmatine. The candidate and reference microorganisms were resistant to 10 of 21 and 5 of 21 antibiotics, respectively. The isolates exhibited hydrophobic, auto-aggregation and coaggregation properties. These three properties were exhibited more (p < 0.05) by the reference than the potential probiotics. The ability of the potential probiotics to attach onto the goat ileum (7.3-8.0 log cfu/cm²) was comparable to that of Lb. rhamnosus yoba 2012 (7.6 log cfu/cm²). The four LAB inhibited E. coli, S. aureus, and S. enterica to the same extent (p < 0.05). The findings indicated potential probiotic activity of the starter cultures. However, further in vivo examination of these isolates is required to confirm their probiotic capabilities.

Probiotics and Covid-19

Coronavirus disease 2019 (COVID-19) has become pandemic very rapidly at the beginning of 2020. In the rush to possible therapeutic options, probiotics administration has been proposed mainly based on indirect observation. Some evidence of COVID-19 effects on intestinal microbiota dysbiosis has been shown and probiotics have been considered for their efficacy in the management of respiratory tract viral infections. These observations could be reinforced by the more and more evident existence of a lung-gut axis, suggesting the modulation of gut microbiota among the approaches to the COVID-19 prevention and treatment. As different possible roles of probiotics in this extremely severe illness have been contemplated, the aim of this work is to collect all the currently available information related to this topic, providing a starting point for future studies focussing on it.

The Potential Effects of Probiotics and ω-3 Fatty Acids on Chronic Low-Grade Inflammation

Chronic low-grade inflammation negatively impacts health and is associated with aging and obesity, among other health outcomes. A large number of immune mediators are present in the digestive tract and interact with gut bacteria to impact immune function. The gut microbiota itself is also an important initiator of inflammation, for example by releasing compounds such as lipopolysaccharides (LPS) that may influence cytokine production and immune cell function. Certain nutrients (e.g., probiotics, ω-3 fatty acids [FA]) may increase gut microbiota diversity and reduce inflammation. Lactobacilli and Bifidobacteria, among others, prevent gut hyperpermeability and lower LPS-dependent chronic low-grade inflammation. Furthermore, ω-3 FA generate positive effects on inflammation-related conditions (e.g., hypertriglyceridemia, diabetes) by interacting with immune, metabolic, and inflammatory pathways. Ω-3 FA also increase LPS-suppressing bacteria (i.e., Bifidobacteria) and decrease LPS-producing bacteria (i.e., Enterobacteria). Additionally, ω-3 FA appear to promote short-chain FA production. Therefore, combining probiotics with ω-3 FA presents a promising strategy to promote beneficial immune regulation via the gut microbiota, with potential beneficial effects on conditions of inflammatory origin, as commonly experienced by aged and obese individuals, as well as improvements in gut-brain-axis communication.

Gut Microbiota and Gestational Diabetes Mellitus: A Review of Host-Gut Microbiota Interactions and Their Therapeutic Potential

Gestational diabetes mellitus (GDM) is defined as impaired glucose tolerance recognized during pregnancy. GDM is associated with metabolic disorder phenotypes, such as obesity, low-grade inflammation, and insulin resistance. Following delivery, nearly half of the women with a history of GDM have persistent postpartum glucose intolerance and an increased risk of developing type 2 diabetes mellitus (T2DM), as much as 7-fold. The alarming upward trend may worsen the socioeconomic burden worldwide. Accumulating evidence strongly associates gut microbiota dysbiosis in women with GDM, similar to the T2DM profile. Several metagenomics studies have shown gut microbiota, such as Ruminococcaceae, Parabacteroides distasonis, and Prevotella, were enriched in women with GDM. These microbiota populations are associated with metabolic pathways for carbohydrate metabolism and insulin signaling, suggesting a potential "gut microbiota signature" in women with GDM. Furthermore, elevated expression of serum zonulin, a marker of gut epithelial permeability, during early pregnancy in women with GDM indicates a possible link between gut microbiota and GDM. Nevertheless, few studies have revealed discrepant results, and the interplay between gut microbiota dysbiosis and host metabolism in women with GDM is yet to be elucidated. Lifestyle modification and pharmacological treatment with metformin showed evidence of modulation of gut microbiota and proved to be beneficial to maintain glucose homeostasis in T2DM. Nonetheless, post-GDM women have poor compliance toward lifestyle modification after delivery, and metformin treatment remains controversial as a T2DM preventive strategy. We hypothesized modulation of the composition of gut microbiota with probiotics supplementation may reverse postpartum glucose intolerance in post-GDM women. In this review, we addressed gut microbiota dysbiosis and the possible mechanistic links between the host and gut microbiota in women with GDM. Furthermore, this review highlights the potential therapeutic use of probiotics in post-GDM women as a T2DM preventive strategy.

Potential Elimination of Human Gut Resistome by Exploiting the Benefits of Functional Foods

Recent advances in technology over the last decades have strived to elucidate the diverse and abundant ecosystem of the human microbiome. The intestinal microbiota represents a densely inhabited environment that offers a plethora of beneficial effects to the host's wellbeing. On the other hand, it can serve as a potential reservoir of Multi-Drug Resistant (MDR) bacteria and their antibiotic-resistant genes (ARgenes), which comprise the "gut resistome." ARgenes, like antibiotics, have been omnipresent in the environment for billions of years. In the context of the gut microbiome, these genes may conflate into exogenous MDR or emerge in commensals due to mutations or gene transfers. It is currently generally accepted that Antimicrobial Resistance (AMR) poses a serious threat to public health worldwide. It is of paramount importance that researchers focus on, amongst other parameters, elaborating strategies to manage the gut resistome, particularly focusing on the diminution of AMR. Potential interventions in the gut microbiome field by Fecal Microbiota Transplant (FMT) or functional foods are newly emerged candidates for the uprooting of MDR strains and restoring dysbiosis and resilience. Probiotic nutrition is thought to diminish gut colonization from pathobionts. Yet only a few studies have explored the effects of antibiotics use on the reservoir of AR genes and the demanding time for return to normal by gut microbiota-targeted strategies. Regular administration of probiotic bacteria has recently been linked to restoration of the gut ecosystem and decrease of the gut resistome and AR genes carriers. This review summarizes the latest information about the intestinal resistome and the intriguing methods of fighting against AMR through probiotic-based methods and gut microbial shifts that have been proposed. This study contains some key messages: (1) AMR currently poses a lethal threat to global health, and it is pivotal for the scientific community to do its utmost in fighting against it; (2) human gut microbiome research, within the last decade especially, seems to be preoccupied with the interface of numerous diseases and identifying a potential target for a variety of interventions; (3) the gut resistome, comprised of AR genesis, presents very early on in life and is prone to shifts due to the use of antibiotics or dietary supplements; and (4) future strategies involving functional foods seem promising for the battle against AMR through intestinal resistome diminution.

Effect of probiotics on obesity-related markers per enterotype: a double-blind, placebo-controlled, randomized clinical trial

Background

Prevention and improvement of disease symptoms are important issues, and probiotics are suggested as a good treatment for controlling the obesity. Human gut microbiota has different community structures. Because gut microbial composition is assumed to be linked to probiotic function, this study evaluated the efficacy of probiotics on obesity-related clinical markers according to gut microbial enterotype.

Methods

Fifty subjects with body mass index over 25 kg/m² were randomly assigned to either the probiotic or placebo group. Each group received either unlabeled placebo or probiotic capsules for 12 weeks. Body weight, waist circumference, and body composition were measured every 3 weeks. Using computed tomography, total abdominal fat area and visceral fat area were measured. Blood and fecal samples were collected before and after the intervention for biochemical parameters and gut microbial compositions analysis.

Results

Gut microbial compositions of all the subjects were classified into two enterotypes according to Prevotella/Bacteroides ratio. The fat percentage, blood glucose, and insulin significantly increased in the Prevotella-rich enterotype of the placebo group. The obesity-related markers, such as waist circumference, total fat area, visceral fat, and ratio of visceral to subcutaneous fat area, were significantly reduced in the probiotic group. The decrease of obesity-related markers was greater in the Prevotella-rich enterotype than in the Bacteroides-rich enterotype.

Conclusion

Administration of probiotics improved obesity-related markers in obese people, and the efficacy of probiotics differed per gut microbial enterotype and greater responses were observed in the Prevotella-dominant enterotype.

Isolation and characterization of vaginal Lactobacillus spp. in dromedary camels (Camelus dromedarius): in vitro evaluation of probiotic potential of selected isolates

Lactobacillus spp. is one of the beneficial lactic acid producing microbiota in the vagina, which is important for a healthy vaginal environment. However, little is known about vaginal Lactobacillus in dromedary camels (Camelus dromedarius). Therefore, this study aimed to isolate vaginal lactic acid bacteria (LAB) in dromedary camels and to study the probiotic potential of selected isolates. A total of 75 vaginal swabs were collected from pluriparous, non-pregnant, non-lactating dromedary camels. The LAB were isolated using deMan, Rogosa and Sharpe broth and agar media. Suspected LAB isolates were subjected to catalase testing and Gram staining and examined for indole production, nitrate reduction, hemolytic activity, cell surface hydrophobicity, auto- and coaggregation, antibacterial activity and characterized by 16S rRNA amplification and sequencing. Eighteen LABs were isolated from the 75 vaginal swabs. Among the 18 LAB isolates, six were Lactobacillus plantarum, eight were Lactobacillus fermentum, and four were Lactobacillus rhamnosus. None of the LAB isolates was hemolytic and only four LAB were H2O2 producing. The percentage of hydrophobicity ranged from 0% to 49.6%, 0% to 44.3% and 0% to 41.6% for hexadecane, xylene and toluene, respectively. All isolates showed higher (P < 0.05) autoaggregation after 24 h of incubation compared to 4 h. Furthermore, all LAB showed higher coaggregation (P < 0.05) and antimicrobial activity toward Staphylococcus aureus than to Escherichia coli. All LAB isolates were vancomycin resistant and sensitive to streptomycin, erythromycin, kanamycin and chloramphenicol. Only, three LAB isolates were resistant to tetracycline. The dromedary camel vaginal LAB isolates exhibited varying degrees of in vitro probiotic properties tested in this study and showed promising activity against the most common bacterial causes of endometritis in dromedary camels. Further investigation of the in vivo effect of these isolates is warranted.

The protective effects of enriched citrulline fermented milk with Lactobacillus helveticus on the intestinal epithelium integrity against Escherichia coli infection

This study examined the protective effects of citrulline enriched-fermented milk with live Lactobacillus helveticus ASCC 511 (LH511) on intestinal epithelial barrier function and inflammatory response in IPEC-J2 cells caused by pathogenic Escherichia coli. Five percent (v/v) of fermented milk with live LH511 and 4 mM citrulline (5%LHFM_Cit-4mM) significantly stimulated the population of IPEC-J2 cells by 36% as determined by MTT assay. Adhesion level of LH511 was significantly increased by 9.2% when incubated with 5%LHFM_Cit-4mM and 5%LHFM_Cit-4mM reduced the adhesion of enterohemorrhagic (EHEC) and entero-invasive (EIEC) E. coli in IPEC-J2 cells by 35.79% and 42.74%, respectively. Treatment with 5%LHFM_Cit-4mM ameliorated lipopolysaccharide (LPS) from E. coli O55:B5 induced activated inflammatory cytokines expression (TNF-α, IL-6 and IL-8) and concentration (IL-6 and IL-8) and early apoptosis. It restored the transepithelial electrical resistance (TEER) and regulated the expression and distribution of tight junction (TJ) proteins (zonula occluden-1 (ZO-1), occludin and claudin-1), toll-like receptors (TLRs) (TLR2 and TLR4) and negative regulators of TLRs signalling pathway (A20 and IRAK-M). In conclusion, our findings suggested that 5%LHFM_Cit-4mM might have the positive effects on improving and maintaining the intestinal epithelial cell integrity and inflammatory response under both normal and pathogenic LPS-stimulated conditions.

A Culture-Independent Method for Enumeration of Viable Load of Lactobacillus acidophilus NCFM by using Real-Time PCR

The study was performed to develop a non-culture method to quantify viable loads of Lactobacillus acidophilus NCFM using RNA-based molecular technique. The ‘growth curve’ and ‘cycle threshold curve’ were developed respectively by plate counting and using cycle threshold (CT) values. ‘Standard curve’ was constructed using cells per milliliter and relative CT values. A maximum viable count (1.5 ± 0.15) × 1010 cells/mL with a minimum CT value 20.18 ± 0.56 was achieved following 18 h of growth. The two parameters were inversely proportional to each other over the exponential growth. The ‘standard curve’ corresponded to equation y = 2E + 28e−2.034x (y = cells/mL, x = CT value; R2 = 0.993), and no sample showed significant difference between ‘plate count’ and relative ‘PCR count’ following the validation process. Industrial adaptation of this method in dairy processing could potentially contribute to a faster enumeration of viable L. acidophilus NCFM compared to plate counting.

Characterization of Bacteriocin-Producing Lactic Acid Bacteria Isolated from Native Fruits of Ecuadorian Amazon

Tropical, wild-type fruits are considered biodiverse "hotspots" of microorganisms with possible functional characteristics to be investigated. In this study, several native lactic acid bacteria (LAB) of Ecuadorian Amazon showing highly inhibitory potential were identified and characterized. Based on carbohydrate fermentation profile and 16S rRNA gene sequencing, seven strains were assigned as Lactobacillus plantarum and one strain as Weissella confusa. Using agar-well diffusion method the active synthetized components released in the neutralized and hydroxide peroxide eliminated cell-free supernatant were inhibited by proteolytic enzymes, while the activity was maintained stable after the treatment with catalase, lysozyme, α-amylase and lipase suggesting their proteinaceous nature. The inhibitory activity was stimulated by acidic conditions, upon exposure to high heat and maintained stable at different ranges of sodium chloride (4-10%). The DNA sequencing analysis confirmed the presence of plw structural gene encoding for plantacirin W in the selected L. plantarum strains. Moreover, we showed that the active peptides of Cys5-4 strains contrast effectively, in a bactericidal manner, the growth of food borne E. coli UTNEc1 and Salmonella UTNSm2, with about tree fold reduction of viable counts at the early stage of the target cell growth. The results indicated that the bacteriocin produced by selected native lactic acid bacteria strains has elevated capacity to suppress several pathogenic microorganisms implying their potential as antimicrobial agents or food preservatives.

Evaluation of adherence and anti-infective properties of probiotic Lactobacillus fermentum strain 4-17 against Escherichia coli causing urinary tract infection in humans

Gastrointestinal (GI) infection is one of the most common types of infectious diseases. Application of probiotic strains in the control of such infections represents a promising approach. In this study, Lactobacillus fermentum strain 4-17 was isolated from kashkineh, an Iranian cereal fermented food, and identified by sequencing its 16S rRNA gene using universal primers. Its probiotic features, including resistance to acid, bile tolerance, antibacterial activity, resistance to intestinal and gastric juices, and hydrophobicity were evaluated. The ability of this strain to adhere to human intestinal cells as well as the anti-adhesive effect of L. fermentum strain 4-17 against E. coli isolated from patients with urinary tract infection was investigated. L. fermentum strain 4-17 was capable of surviving at various conditions such as low pH values, bile salts exposure, and GI tract environment. It showed 43% cell hydrophobicity. The adhesion level of L. fermentum strain 4-17 to human colon adenocarcinoma Caco-2 cells was 8.5% which was also confirmed by scanning electron microscopy (SEM). Furthermore, this strain showed appropriate anti-adhesive properties (including competition, inhibition and replacement properties) against human pathogenic bacteria. These data suggest that L. fermentum strain 4-17 could be examined further for its useful effects and introduced as a novel candidate probiotic to control GI infection disease.

Dietary supplementation of probiotic Bacillus coagulans ATCC 7050, improves the growth performance, intestinal morphology, microflora, immune response, and disease confrontation of Pacific white shrimp, Litopenaeus vannamei

The present study assessed the effects of probiotic bacterium Bacillus coagulans ATCC 7050 (BC) fed at different inclusion levels (0 (BO), 1 × 10⁶ (BC1), 1 × 10⁷ (BC2) and 1 × 10⁸ (BC3) CFU g^-1 feed) on growth, feed utilization, body composition, intestinal morphology, microflora, immune response, and resistance to Vibrio parahaemolyticus infection in Litopenaeus vannamei. After 56 days of the feeding trial, the survival rate ranged from 83.33 to 94.17% with no significant difference between dietary treatments (P > 0.05). Dietary probiotic supplementation also affected the intestinal microflora composition. At the phylum level, Proteobacteria accounted for the majority of bacteria followed by Bacteroidetes irrespective of the group. At the genus level, the abundance of opportunistic pathogenic bacteria, such as Vibrio, Tenacibaculum, and Photobacterium significantly decreased (P < 0.05) with an increasing probiotic concentration, and BC3 group experiencing the least. Additionally, increasing probiotic inclusion in diet downregulated the abundance of Muricauda, Kangiella, and Shewanella in shrimps, with the least, observed in the BC3 group. However, beneficial bacteria Pseudoalteromonas significantly increased (P < 0.05) in the intestines of shrimp fed BC3 diet (P < 0.05) compared to other groups including the control. Compared to the control, a significant increase (P < 0.05) of the probiotic treated groups in the final weight, weight gain rate (WGR), specific growth rate (SGR), condition factor (K), activity of lysozyme (LYZ), acid phosphatase (ACP), superoxide dismutase (SOD), total protein (TP), albumin (ALB) in serum, glutathione peroxidase (GSH-Px) in serum and liver, and a significant decrease (P < 0.05) in feed conversion ratio (FCR), triglyceride (TG) in serum, and Malondialdehyde (MDA) in serum and liver were achieved. Increasing probiotic treatment again improved the digestive ability, thus; a significant increase in the activities of lipase, amylase, trypsin, and an enhancement in the villus height, villus width, and muscle thickness of the intestines of the shrimps which correspondingly alleviated intestinal injury. Furthermore, the supplementation of probiotics in challenge test significantly (P < 0.05) enhanced the resistance of shrimp against V. parahaemolyticus infection recording BC3 to receive the highest relative percentage survival (RPS) value of 76%. In conclusion, higher inclusion levels of probiotic BC at 1 × 10⁸ CFU g^-1 feed (BC3) in diets can be considered to enhance the growth, intestinal morphology and microflora, immune response and resistance to Vibrio parahaemolyticus of L. vannamei.

Persistent infection by Salmonella enterica servovar Typhimurium: are synbiotics a therapeutic option? – a case report

Little is known about the prevalence of persistent human infections by nontyphoidal Salmonella (NTS). Recently published study results indicate that a small fraction (at least 2.2%) of NTS-infected patients continue to shed Salmonella for an extended period of time (up to years). Despite the recommendation not to use antibiotics for the treatment of uncomplicated NTS-Salmonella infection, little treatment guidance is available. Clinical findings from a NTS-patient indicate that administration of synbiotics (probiotic bacteria plus prebiotic) might be considered as a treatment option. We report data of a patient who was treated with a synbiotic preparation containing nine different probiotic bacteria and the prebiotic fructooligosaccharides (FOS). Starting from day one of the treatment, the patient experienced an improvement of symptoms and was symptom-free at the end of a 10 days treatment course. After finishing the treatment, the stool proved to be Salmonella enterica serovar Typhimurium negative. In vitro pathogenic inhibition studies showed the inhibitory effects of the multistrain synbiotic mixture against S. Typhimurium. Growth of S. Typhimurium was also inhibited by individual bacterial strains making part of the composition of the mixture. However, he inhibitory effects of individual strains varied significantly, with those of Streptococcus thermophilus St-21 and Lactobacillus helveticus SP-27 exhibiting the strongest inhibitory effect. Persistent infections by S. Typhimurium are a severe concern for the affected patients. Besides the symptomatic burden, infected persons are banned from work in certain areas (e.g. food related service). In addition, patients with persistent S. Typhimurium infections are a threat for the public health in general, as they serve as a reservoir for NTS transmission. The findings indicate that treatment with a synbiotic preparation might provide a treatment option for persistent S. Typhimurium infections. More clinical data have to be gathered to confirm the relevance of this potential treatment approach.

Comparative studies of versatile extracellular proteolytic activities of lactic acid bacteria and their potential for extracellular amino acid productions as feed supplements

BACKGROUND

Increasing understanding on the functions of amino acids (AA) has led to new commercial applications and expansion of the worldwide markets. However, the current technologies rely heavily on non-food grade microorganism and chemical synthesis for the production of AA. Several studies reported that lactic acid bacteria (LAB) have the capability of producing AA owing to their well-established proteolytic system and amino acid biosynthesis genes. Hence, the objectives of this study were to explore the extracellular proteolytic activity of LAB isolated from various Malaysian fermented foods and their potential to produce AA extracellularly as feed supplements.

RESULTS

All the studied LAB isolates were versatile extracellular protease producers, whereby extracellular protease activities were detected from acidic to alkaline pH (pH 5, pH 6.5, pH 8) using qualitative and quantitative proteolytic assays. The highest proteolytic activity at pH 5 (15.76 U/mg) and pH 8 (19.42 U/mg) was achieved by Lactobacillus plantarum RG14, while Lactobacillus plantarum RS5 exhibited the highest proteolytic activity of 17.22 U/mg at pH 6.5. As for the results of AA production conducted in de Man, Rogosa and Sharpe medium and analysed by high pressure liquid chromatography system, all LAB isolates were capable of producing an array of AA. Generally, Pediococcus sp. showed greater ability for AA production as compared to Lactobacillus sp. Moreover, the studied LAB were able to produce a few major feed supplement AA such as methionine, lysine, threonine and tryptophan. P. pentosaceus TL-3 recorded the highest methionine and threonine productivity of 3.72 mg/L/h and 5.58 mg/L/h respectively. However, L. plantarum I-UL4 demonstrated a lysine productivity of 1.24 mg/L/h, while P. acidilactici TP-6 achieved up to 1.73 mg/L/h of tryptophan productivity.

CONCLUSION

All the 17 studied LAB isolates possessed versatile extracellular proteolytic system and have vast capability of producing various amino acids including a few major feed supplement AA such as methionine, lysine, threonine and tryptophan. Despite AA production was strain dependent, the studied LAB isolates possessed vast potential and can be exploited further as a bio-agent or an alternative amino acids and bioactive peptide producers.

Randomised clinical trial: Bifidobacterium lactis NCC2818 probiotic vs placebo, and impact on gut transit time, symptoms, and gut microbiology in chronic constipation

BACKGROUND

Constipation is a prevalent gastrointestinal disorder. Patient dissatisfaction with prescribed medications is common, and there is need for alternative management strategies. Evidence shows that Bifidobacterium species may be beneficial in constipation.

AIM

To investigate changes in physiological and clinical measures of gut function in patients with chronic constipation following the consumption of Bifidobacterium lactis NCC2818, compared to placebo.

METHODS

Participants were randomised to a 4-week supplementation with B. lactis NCC2818 (1.5 x 10¹⁰ CFU/d) or placebo. Gut transit time was measured using a radio-opaque marker, while symptoms and quality of life were assessed using validated questionnaires. Gut microbiota composition was assessed using quantitative polymerase chain reaction. Analysis of covariance was used for normally distributed variables, and Mann-Whitney test for non-normally distributed variables.

RESULTS

Seventy-five participants were randomised. There was no significant difference between the probiotic and placebo groups in gut transit time change from baseline to week 2 (-11.7 hours, SD 33.0 hours vs -12.9 hours, SD 33.6 hours; P = 0.863) or to week 4 (-20.4 hours, SD 32.5 h vs -8.7 hours, SD 33.8 hours; P = 0.103). There were also no improvements in stool output, symptoms, or quality of life. No differences were found in Bifidobacterium concentrations between the probiotic and placebo groups at week 4 (9.5 log₁₀ /g dry faeces, SD 0.3 vs 9.4 log₁₀ /g, SD 1.0; P = 0.509).

CONCLUSIONS

Bifidobacterium lactis NCC2818 was not effective in the management of mild chronic constipation. This study highlights the importance of further studies and their publication to better understand the strain-specific effects of probiotics.

Bovine colostrum-driven modulation of intestinal epithelial cells for increased commensal colonisation

Nutritional intake may influence the intestinal epithelial glycome and in turn the available attachment sites for bacteria. In this study, we tested the hypothesis that bovine colostrum may influence the intestinal cell surface and in turn the attachment of commensal organisms. Human HT-29 intestinal cells were exposed to a bovine colostrum fraction (BCF) rich in free oligosaccharides. The adherence of several commensal bacteria, comprising mainly bifidobacteria, to the intestinal cells was significantly enhanced (up to 52-fold) for all strains tested which spanned species that are found across the human lifespan. Importantly, the changes to the HT-29 cell surface did not support enhanced adhesion of the enteric pathogens tested. The gene expression profile of the HT-29 cells following treatment with the BCF was evaluated by microarray analysis. Many so called "glyco-genes" (glycosyltransferases and genes involved in the complex biosynthetic pathways of glycans) were found to be differentially regulated suggesting modulation of the enzymatic addition of sugars to glycoconjugate proteins. The microarray data was further validated by means of real-time PCR. The current findings provide an insight into how commensal microorganisms colonise the human gut and highlight the potential of colostrum and milk components as functional ingredients that can potentially increase commensal numbers in individuals with lower counts of health-promoting bacteria.

Shear-Enhanced Dynamic Adhesion of Lactobacillus rhamnosus GG on Intestinal Epithelia: Correlative Effect of Protein Expression and Interface Mechanics

The oral uptake of probiotic microorganisms as food additives is one widely used strategy to sustain and improve the homeostasis of intestinal microbiota that protect the intestinal epithelia from attack by pathogenic bacteria. Once delivered to the ileum and colon, probiotics must adhere and form colonies on mucus that coats the surface of intestinal epithelial cells. Although an increasing amount of knowledge about the genetic and molecular level mechanisms of probiotics-mucus interactions has been accumulated, little is known about the physicochemical aspects of probiotics-mucus interactions under physiological shear in intestines. In this study, we established well-defined models of intestinal epithelial cell monolayers based on two major constituents of gut epithelia, enterocytes and goblet cells. First, the formation of a polarized cell monolayer sealed by tight junctions was monitored by transepithelial electrical resistance over time. The establishment of tight junctions and secretion of mucus proteins (mucin) was confirmed by immunofluorescence staining. In the next step, we measured the elasticity of cell monolayer surfaces by indentation using particle-assisted atomic force microscopy. The effective elastic modulus of goblet cell-like cells was 30 times smaller compared to that of enterocyte-like cells, which can be attributed to the secretion of a 3 μm thick mucin layer. As probiotics, we used Lactobacillus rhamnosus GG (LGG), which is one of the most widely used strains as food additives. To investigate the dynamic adhesion of LGG to the intestine model surface, we transferred the epithelial cell monolayer into a microfluidic chamber. A distinct difference in dynamic adhesion between two cell types was observed, which could be attributed to the difference in the mucin expression amount. Remarkably, we found that the dynamic LGG adhesion is enhanced by the increase in shear stress, showing a maximum binding efficiency at 0.3 Pa. Finally, we examined the persistence of LGG adhesion by a stepwise increase in the shear stress exerted on adherent LGG, demonstrating that LGG could withstand high shear stress even beyond that of physiological stress. The obtained results present a large potential to quantitatively understand the influence of engineered foods and probiotics on the homeostasis of microbiota on the surface of intestinal epithelia.

Antagonistic effect of Saccharomyces cerevisiae KTP and Issatchenkia occidentalis ApC on hyphal development and adhesion of Candida albicans

The morphological transition from yeast to a hyphal form, as well as the adhesion capability to the gastrointestinal tract, are implicated virulent determinant in Candida albicans and could be potential targets for prevention of the opportunistic pathogen. Based on this rationale, two yeast strains Saccharomyces cerevisiae KTP and Issatchenkia occidentalis ApC along with reference strain Saccharomyces boulardii NCDC 363 were screened for the probiotic potential. Characters like pH, temperature, bile, simulated gastrointestinal juice tolerance tests, and Caco-2 cell line adhesion assay were determined in the present study. Further, the evaluation of its impact on C. albicans morphological transition and adhesion was assessed using microtitre germ tube test. In terms of probiotic characteristics, both the strains were tolerant to pH 2.5 and the presence of bile (0.3 to 0.6%) with an optimum growth temperature of 37°C. The strain KTP was also resistant to simulated gastric and intestinal juices as compared to control (13% and 41%, respectively) and NCDC 363 (55% and 35%, respectively). In contrast, both the yeasts had reduced adhesiveness to Caco-2 monolayer. Candida virulence in in vitro systems indicated that treatment of live probiotic yeast cells (108 ml) effectively reduced the filamentation and adhesion of C. albicans. The S. cerevisiae KTP had a profound effect on the hyphal development and adhesion when compared to the ApC and NCDC 363. The strain significantly reduced (P < .05) the hyphal growth in co-cultivated (93% and 94%, respectively) and pre-existing hyphae (54% and 68%) of strains C. albicans 183 and 1151. Isolates KTP and ApC also reduced the adhesion (≈ 22% and 41%, respectively) and transition of blastoconidia at two hours of incubation in abiotic surface. This study provides knowledge on the effect of potential probiotic yeasts such as Saccharomyces and non- Saccharomyces strains against virulence characteristic of Candida albicans.

Lactobacillus Dominate in the Intestine of Atlantic Salmon Fed Dietary Probiotics

Probiotics, the live microbial strains incorporated as dietary supplements, are known to provide health benefits to the host. These live microbes manipulate the gut microbial community by suppressing the growth of certain intestinal microbes while enhancing the establishment of some others. Lactic acid bacteria (LAB) have been widely studied as probiotics; in this study we have elucidated the effects of two fish-derived LAB types (RII and RIII) on the distal intestinal microbial communities of Atlantic salmon (Salmo salar). We employed high-throughput 16S rRNA gene amplicon sequencing to investigate the bacterial communities in the distal intestinal content and mucus of Atlantic salmon fed diets coated with the LABs or that did not have microbes included in it. Our results show that the supplementation of the microbes shifts the intestinal microbial profile differentially. LAB supplementation did not cause any significant alterations in the alpha diversity of the intestinal content bacteria but RIII feeding increased the bacterial diversity in the intestinal mucus of the fish. Beta diversity analysis revealed significant differences between the bacterial compositions of the control and LAB-fed groups. Lactobacillus was the dominant genus in LAB-fed fish. A few members of the phyla Tenericutes, Proteobacteria, Actinobacteria, and Spirochaetes were also found to be abundant in the LAB-fed groups. Furthermore, the bacterial association network analysis showed that the co-occurrence pattern of bacteria of the three study groups were different. Dietary probiotics can modulate the composition and interaction of the intestinal microbiota of Atlantic salmon.

Lactobacillus caseiLC2W can inhibit the colonization ofEscherichia coliO157:H7in vivoand reduce the severity of colitis

L. caseiLC2W can inhibit the colonization of O157:H7 in mice and its prevention effect is stronger than the treatment effect.

Matrix-wise evaluation of in vivo and in vitro efficiencies of L. rhamnosus GG-fortified beverages

The interactions between phenolic compounds and gut microbiota, have gained much attention due to their beneficial effect on humans. The study was also conceived keeping in view the growing popularity of probiotics and emerging interest in designing plant based matrices for probiotic delivery. The synergistic relationship between probiotic, Lactobacillus rhamnosus GG (LR) (ATCC 53103) and phenolic compounds of fruit matrices, sea buckthorn (SBT) and apple juice (APJ) was evaluated on TNBS induced enterocolitis in a zebrafish model (Danio rerio). Addition of LR to SBT matrix conferred higher protection against inflammation than LR in APJ matrix. This could be due to higher content of phenolic compounds in SBT. Isorhamnetin was identified as the predominant phenolic in SBT. The juice matrices were also evaluated for their flow and viscoelastic properties. The consistency index (K) and flow behaviour index (η) were derived from evaluating the shear strength. All the tested juice matrices demonstrated shear-thinning properties. Effect of the matrices on other functionalities of LR during storage period of 14 days was also evaluated. No significant changes were observed on cell surface hydrophobicity depicting protective action of the matrix components on the probiotic strain. Gastrointestinal tolerance increased on Day 7 and 14. Principal Component Analysis of the anti-microbial potential of the probiotic beverage formulations against pathogenic and food spoilage strains showed higher antagonistic ability of LR in SBT during the 14 days storage. The key findings suggest probiotic strain may behave differently in different food matrices. The sustainable functionality of the probiotic strain can be achieved even during the shelf period by optimum design of the delivery matrix.

Multiple mechanisms applied by Lactobacillus pentosus AT6 to mute the lethal effects of Salmonella in a mouse model

Probiotics are now prevalent world-wide, as functional food supplements with many benefits for humans and animals, such as protective effects against pathogenic infection. We showed that oral supplementation of Lactobacillus pentosus AT6 (AT6) decreased the mortality rate of mice with Salmonella infection. A series of experiments showed that the protective effects of AT6 on mice involved multiple mechanisms, including (1) the inhibition of Salmonella Typhimurium growth by AT6 or its cell-free culture supernatants (CFCSs); (2) the reduction of the bacterial loads of Salmonella Typhimurium in intestinal contents and internal organs, such as the liver and spleen; (3) the inhibition of adhesion and invasion of Salmonella Typhimurium into intestinal epithelial cells; and (4) the regulation of host immunities by modifying the production of a chain of cytokines. In conclusion, AT6 inhibited Salmonella infection via multiple mechanisms and therefore has great potential for the development of functional foods with anti-Salmonella activities.

Salmonella infection - prevention and treatment by antibiotics and probiotic yeasts: a review

Global Salmonella infection, especially in developing countries, is a health and economic burden. The use of antibiotic drugs in treating the infection is proving less effective due to the alarming rise of antibiotic-resistant strains of Salmonella, the effects of antibiotics on normal gut microflora and antibiotic-associated diarrhoea, all of which bring a growing need for alternative treatments, including the use of probiotic micro-organisms. However, there are issues with probiotics, including their potential to be opportunistic pathogens and antibiotic-resistant carriers, and their antibiotic susceptibility if used as complementary therapy. Clinical trials, animal trials and in vitro investigations into the prophylactic and therapeutic efficacies of probiotics have demonstrated antagonistic properties against Salmonella and other enteropathogenic bacteria. Nonetheless, there is a need for further studies into the potential mechanisms, efficacy and mode of delivery of yeast probiotics in Salmonella infections. This review discusses Salmonella infections and treatment using antibiotics and probiotics.

Infant colic: mechanisms and management

Infant colic is a commonly reported phenomenon of excessive crying in infancy with an enigmatic and distressing character. Despite its frequent occurrence, little agreement has been reached on the definition, pathogenesis or the optimal management strategy for infant colic. This Review aims to delineate the definitional entanglement with the Rome IV criteria, which were published in 2016, as the leading, most recent diagnostic criteria. Moreover, neurogenic, gastrointestinal, microbial and psychosocial factors that might contribute to the pathophysiology of infant colic are explored. This Review underlines that a comprehensive medical history and physical examination in the absence of alarm symptoms serve as guidance for the clinician to a positive diagnosis. It also highlights that an important aspect of the management of infant colic is parental education and reassurance. Management strategies, including behavioural, dietary, pharmacological and alternative interventions, are also discussed. Owing to a lack of large, high-quality randomized controlled trials, none of these therapies are strongly recommended. Finally, the behavioural and somatic sequelae of infant colic into childhood are summarized.

Effect of Propionibacterium freudenreichii on Salmonella multiplication, motility, and association with avian epithelial cells1

We investigated the effects of a probiotic bacterium, Propionibacterium freudenreichii, on Salmonella multiplication, motility, and association to and invasion of avian epithelial cells in vitro. Two subspecies of P. freudenreichii (P. freudenreichii subsp. freudenreichii and P. freudenreichii subsp. shermanii) were tested against 3 Salmonella serotypes in poultry, namely, S. Enteritidis, S. Typhimurium, and S. Heidelberg, using co-culture-, motility, multiplication, cell association, and invasion assays. Both strains of P. freudenreichii were effective in reducing or inhibiting multiplication of all 3 Salmonella serotypes in co-culture and turkey cecal contents (P ≤ 0.05). P. freudenreichii significantly reduced Salmonella motility (P ≤ 0.05). Cell culture studies revealed that P. freudenreichii associated with the avian epithelial cells effectively and reduced S. Enteritidis, S. Heidelberg, and S. Typhimurium cell association in the range of 1.0 to 1.6 log10 CFU/mL, and invasion in the range of 1.3 to 1.5 log10 CFU/mL (P ≤ 0.05), respectively. Our current in vitro results indicate the potential of P. freudenreichii against Salmonella in poultry. Follow-up in vivo studies are underway to evaluate this possibility.

Probiotic properties of native Lactobacillus spp. strains for dairy calves

The use of native microorganisms with probiotic capacity is an alternative tool for the treatment and prevention of several diseases that affect animals, such as neonatal calf diarrhoea. The selection of probiotic strains within a collection is based on different in vitro and in vivo assays, which predict their potential. The aim of this study was to characterise a group of native Lactobacillus spp. strains isolated from faeces of healthy calves using an in vitro approach and to assess their ability to colonise the gastrointestinal tract (GIT) of calves. Native Lactobacillus spp. strains were evaluated on their capacity to survive low pH conditions and bile salts presence, biofilm formation and adhesion to both mucus and Caco-2 cells. Based on the in vitro characterisation, four strains (Lactobacillus johnsonii TP1.1, Lactobacillus reuteri TP1.3B, L. johnsonii TP1.6 and Lactobacillus amylovorus TP8.7) were selected to evaluate their capacity to colonise and persist in the GIT of calves. The assessment of enteric persistence involved an in vivo assay with oral administration of probiotics and quantification in faeces of the administered bacterial species with real-time quantitative PCR (qPCR). The study was conducted using 15 calves (1-month-old) which were divided into five groups of three animals, four of which were treated with four different selected strains and one was the control group. Strains TP1.3B and TP1.6 managed to persist in treated animals until ten days after the end of the administration period, indicating that they could be promising candidates for the design of probiotics for calves.

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.

Some probiotic characteristics of a fermented milk product based on microbiota of "Tibetan kefir grains" cultivated in Ukrainian household

The article describes some probiotic properties of fermented product made of natural association of Tibetan kefir grains cultivated in Ukrainian household (UTKG); also, the effect of UTKG microbiota on the growth of pathogenic microbiota and sensitivity to antibiotics was studied. It was found that the test-cultures of oppurtunistic pathogens (Staphylococcus aureus, Bacillus mesentericus, and Mycobacterium luteum) were sensitive; bacteriostatic zone of the test-culture ranged from 21 to 25 mm, and highly sensitive (Proteus vulgaris and Aspergillus niger) bacteriostatic zone exceeded 25 mm to probiotic bacteria of fermented product. UTKG microbiota is also moderately sensitive to multiple antibiotics that allows defining the obtained fermented milk product as functional with therapeutic properties. During the study of the influence of different NaCl and bile concentrations on acid-activity of UTKG it was found that active acid formation occurred at the concentrations up to 4% NaCl in cultivation medium (boiled milk) and at 20% bile and 0.45% phenol. It proves microbial association to be capable of withstanding adverse gastrointestinal conditions and continue developing.

The human gut microbiome in health: establishment and resilience of microbiota over a lifetime

With technological advances in culture-independent molecular methods, we are uncovering a new facet of our natural history by accounting for the vast diversity of microbial life which colonizes the human body. The human microbiome contributes functional genes and metabolites which affect human physiology and are, therefore, considered an important factor for maintaining health. Much has been described in the past decade based primarily on 16S rRNA gene amplicon sequencing regarding the diversity, structure, stability and dynamics of human microbiota in their various body habitats, most notably within the gastrointestinal tract (GIT). Relatively high levels of variation have been described across different stages of life and geographical locations for the GIT microbiome. These observations may prove helpful for the future contextualization of patterns in other body habitats especially in relation to identifying generalizable trends over human lifetime. Given the large degree of complexity and variability, a key challenge will be how to define baseline healthy microbiomes and how to identify features which reflect deviations therefrom in the future. In this context, metagenomics and functional omics will likely play a central role as they will allow resolution of microbiome-conferred functionalities associated with health. Such information will be vital for formulating therapeutic interventions aimed at managing microbiota-mediated health particularly in the GIT over the course of a human lifetime.

The Probiotic Combination of Bifidobacterium longum subsp. infantis CECT 7210 and Bifidobacterium animalis subsp. lactis BPL6 Reduces Pathogen Loads and Improves Gut Health of Weaned Piglets Orally Challenged with Salmonella Typhimurium

Probiotics have been demonstrated to be useful to enhance gut health and prevent gastrointestinal infections in humans. Additionally, some multi-strain probiotic combinations have been suggested to have greater efficacy than single strains. The objective of this study is to demonstrate the potential of a combination of the probiotic strains: Bifidobacterium longum subsp. infantis CECT 7210 (brand name B. infantis IM1®) and B. animalis subsp. lactis BPL6 to enhance gut health and to ameliorate the outcome of a Salmonella challenge using a weaning piglet model. Seventy-two 28-day-old weanling piglets, 7.7 (±0.28) kg of body-weight, were distributed in a 2 × 2 factorial design; treated or not with the probiotic combination and challenged or not with the pathogen. Animals were orally challenged after an adaptation period (Day 8) with a single dose (5 × 108 cfu) of Salmonella Typhimurium. One animal per pen was euthanized on Day 12 (Day 4 post-inoculation [PI]) and Day 16 (Day 8 PI). All parameters responded to the challenge and 4 deaths were registered, indicating a severe but self-limiting challenge. Improvements registered in the challenged animals due to the probiotic were: increased voluntary feed-intake (P probiotic × challenge = 0.078), reduced fecal excretion of Salmonella (P = 0.028 at Day 1 PI and P < 0.10 at Days 3 and 5 PI), decreased rectal temperature (P probiotic × day = 0.048) and improvements in the villous:crypt ratio (P probiotic × challenge < 0.001). Moreover, general probiotic benefits were observed in both challenged and non-challenged groups: decreased diarrhea scores of the PI period (P = 0.014), improved fermentation profiles on Day 8 PI (increased ileal acetic acid [P = 0.008] and a tendency to lower colonic ammonia concentrations [P = 0.078]), stimulation of intestinal immune response by increasing villous intraepithelial lymphocytes (P = 0.015 on Day 8 PI) and an improved villous:crypt ratio (P = 0.011). In conclusion, the multi-strain probiotic had a positive effect on reducing pathogen loads and alleviating animals in a Salmonella challenge. In addition, enhanced gut health and immunity was recorded in all animals receiving the probiotic, indicating an improvement in the post-weaning outcome.

Adhesion of Lactobacilli and their anti-infectivity potential

The probiotic potential of lactic acid bacteria primarily point toward colonizing ability of Lactobacilli as the most important attribute for endowing all the known beneficial effects in a host. Lactobacillus species exert health-promoting function in the gastrointestinal tract through various mechanisms such as pathogen exclusion, maintenance of microbial balance, immunomodulation, and other crucial functions. It has been seen that many surface layer proteins are involved in host adhesion, and play significant role in the modification of some signaling pathways within the host cells. Interaction between different bacterial cell surface proteins and host receptor has been imperative for a better understanding of the mechanism through which Lactobacilli exert their health-promoting functions.

Recent Advances and Understanding of Using Probiotic-Based Interventions to Restore Homeostasis of the Microbiome for the Prevention/Therapy of Bacterial Diseases

The importance of the microbiome in health and disease has galvanized interest in using manipulations of the gastrointestinal ecosystem to prevent and/or combat gut bacterial infections and to restore mucosal homeostasis in patients with generalized microbial imbalances (i.e., dysbiosis), including the human inflammatory bowel diseases, Crohn's disease, and ulcerative colitis. Probiotics, prebiotics, or their combination use (i.e., synbiotics) are one mechanism for modifying the microbiota and exerting direct and indirect effects on the host immune responses and metabolomics profiles. These beneficial effects are transferred through various pathways, including the production of antimicrobial peptides, promoting the growth of beneficial microbes and enhancing immunomodulatory functions via various metabolites. While probiotic therapy has been used empirically for decades with mixed success, the recent advances in molecular and mass spectrophotometric techniques for the characterization of the complexity and diversity of the intestinal microbiome has aided in better understanding of host-microbe interactions. It is important to better understand the functional properties of the microbiome, because it is now clear that the microbiota secretes many metabolites that have a direct impact on host immune responses. This information will improve selection of the most appropriate probiotic strains that selectively target intestinal disease processes.

Bifidobacterium animalis subsp. lactis 420 mitigates the pathological impact of myocardial infarction in the mouse

There is a growing appreciation that our microbial environment in the gut plays a critical role in the maintenance of health and the pathogenesis of disease. Probiotic, beneficial gut microbes, administration can directly attenuate cardiac injury and post-myocardial infarction (MI) remodelling, yet the mechanisms of cardioprotection are unknown. We hypothesised that administration of Bifidobacterium animalis subsp. lactis 420 (B420), a probiotic with known anti-inflammatory properties, to mice will mitigate the pathological impact of MI, and that anti-inflammatory T regulatory (T_reg) immune cells are necessary to impart protection against MI as a result of B420 administration. Wild-type male mice were administered B420, saline or Lactobacillus salivarius 33 (Ls-33) by gavage daily for 14 or 35 days, and underwent ischemia/reperfusion (I/R). Pretreatment with B420 for 10 or 28 days attenuated cardiac injury from I/R and reduced levels of inflammatory markers. Depletion of T_reg cells by administration of anti-CD25 monoclonal antibodies eliminated B420-mediated cardio-protection. Further cytokine analysis revealed a shift from a pro-inflammatory to an anti-inflammatory environment in the probiotic treated post-MI hearts compared to controls. To summarise, B420 administration mitigates the pathological impact of MI. Next, we show that T_reg immune cells are necessary to mediate B420-mediated protection against MI. Finally, we identify putative cellular, epigenetic and/or post-translational mechanisms of B420-mediated protection against MI.

Can probiotics modulate human disease by impacting intestinal barrier function?

Intestinal barrier integrity is a prerequisite for homeostasis of mucosal function, which is balanced to maximise absorptive capacity, while maintaining efficient defensive reactions against chemical and microbial challenges. Evidence is mounting that disruption of epithelial barrier integrity is one of the major aetiological factors associated with several gastrointestinal diseases, including infection by pathogens, obesity and diabetes, necrotising enterocolitis, irritable bowel syndrome and inflammatory bowel disease. The notion that specific probiotic bacterial strains can affect barrier integrity fuelled research in which in vitro cell lines, animal models and clinical trials are used to assess whether probiotics can revert the diseased state back to homeostasis and health. This review catalogues and categorises the lines of evidence available in literature for the role of probiotics in epithelial integrity and, consequently, their beneficial effect for the reduction of gastrointestinal disease symptoms.

Resetting microbiota by Lactobacillus reuteri inhibits T reg deficiency-induced autoimmunity via adenosine A2A receptors

He et al. show that T reg deficiency markedly induces autoimmunity and shifts gut microbiota. Remodeling microbiota by Lactobacillus reuteri was found to inhibit autoimmunity via the metabolite inosine, which interacts with the adenosine A_2A receptor. This finding establishes a link between the gut microbiota, A_2A receptors, and autoimmunity induced by T reg cell deficiency.

Regulatory T (T reg) cell deficiency causes lethal, CD4⁺ T cell–driven autoimmune diseases. Stem cell transplantation is used to treat these diseases, but this procedure is limited by the availability of a suitable donor. The intestinal microbiota drives host immune homeostasis by regulating the differentiation and expansion of T reg, Th1, and Th2 cells. It is currently unclear if T reg cell deficiency–mediated autoimmune disorders can be treated by targeting the enteric microbiota. Here, we demonstrate that Foxp3⁺ T reg cell deficiency results in gut microbial dysbiosis and autoimmunity over the lifespan of scurfy (SF) mouse. Remodeling microbiota with Lactobacillus reuteri prolonged survival and reduced multiorgan inflammation in SF mice. L. reuteri changed the metabolomic profile disrupted by T reg cell deficiency, and a major effect was to restore levels of the purine metabolite inosine. Feeding inosine itself prolonged life and inhibited multiorgan inflammation by reducing Th1/Th2 cells and their associated cytokines. Mechanistically, the inhibition of inosine on the differentiation of Th1 and Th2 cells in vitro depended on adenosine A_2A receptors, which were also required for the efficacy of inosine and of L. reuteri in vivo. These results reveal that the microbiota–inosine–A_2A receptor axis might represent a potential avenue for combatting autoimmune diseases mediated by T reg cell dysfunction.

High Iron-Sequestrating Bifidobacteria Inhibit Enteropathogen Growth and Adhesion to Intestinal Epithelial Cells In vitro

The gut microbiota plays an important role in host health, in particular by its barrier effect and competition with exogenous pathogenic bacteria. In the present study, the competition of Bifidobacterium pseudolongum PV8-2 (Bp PV8-2) and Bifidobacterium kashiwanohense PV20-2 (Bk PV20-2), isolated from anemic infant gut microbiota and selected for their high iron sequestration properties, was investigated against Salmonella Typhimurium (S. Typhi) and Escherichia coli O157:H45 (EHEC) by using co-culture tests and assays with intestinal cell lines. Single and co-cultures were carried out anaerobically in chemically semi-defined low iron (1.5 μM Fe) medium (CSDLIM) without and with added ferrous iron (30 μM Fe). Surface properties of the tested strains were measured by bacterial adhesion to solvent xylene, chloroform, ethyl acetate, and to extracellular matrix molecules, mucus II, collagen I, fibrinogen, fibronectin. HT29-MTX mucus-secreting intestinal cell cultures were used to study bifidobacteria competition, inhibition and displacement of the enteropathogens. During co-cultures in CSDLIM we observed strain-dependent inhibition of bifidobacterial strains on enteropathogens, independent of pH, organic acid production and supplemented iron. Bp PV8-2 significantly (P < 0.05) inhibited S. Typhi N15 and EHEC after 24 h compared to single culture growth. In contrast Bk PV20-2 showed less inhibition on S. Typhi N15 than Bp PV8-2, and no inhibition on EHEC. Affinity for intestinal cell surface glycoproteins was strain-specific, with high affinity of Bp PV8-2 for mucin and Bk PV20-2 for fibronectin. Bk PV20-2 showed high adhesion potential (15.6 ± 6.0%) to HT29-MTX cell layer compared to Bp PV8-2 (1.4 ± 0.4%). In competition, inhibition and displacement tests, Bp PV8-2 significantly (P < 0.05) reduced S. Typhi N15 and EHEC adhesion, while Bk PV20-2 was only active on S. Typhi N15 adhesion. To conclude, bifidobacterial strains selected for their high iron binding properties inhibited S. Typhi N15 and EHEC in co-culture experiments and efficiently competed with the enteropathogens on mucus-producing HT29-MTX cell lines. Further studies in complex gut ecosystems should explore host protection effects of Bp PV8-2 and Bk PV20-2 mediated by nutritional immunity mechanism associated with iron-binding.

Selected Lactobacillus strains isolated from sugary and milk kefir reduce Salmonella infection of epithelial cells in vitro

The isolation of potentially probiotic strains and the subsequent study of their properties are very important steps to gain insight in the health benefits ascribed to sugary and milk kefir. The aim of the present study was to characterise fifteen Lactobacillus strains isolated from these beverages by determining some surface properties and their ability to antagonise enterocyte cell damage after Salmonella infection in vitro. Lactobacillus surface properties were determined by hydrophobicity, autoaggregation, and coaggregation assays with Salmonella. In addition, lactobacilli adhesion to Caco-2/TC-7 cells and the effect on Salmonella invasion were evaluated. Finally, the disassembly of F-actin cytoskeleton on intestinal epithelial cells was assayed in vitro when Salmonella infection was performed in the presence of selected Lactobacillus strains. Ten out of the 15 strains showed a high adhesion capacity to Caco-2/TC-7 cells. Most of the strains were hydrophilic and non-autoaggregating. Strains isolated from sugary kefir were non-coaggregating with Salmonella, while strains Lactobacillus paracasei CIDCA 83120, 83121, 83123, 83124, 8339, 83102 isolated from milk kefir were able to coaggregate after 1 h. L. paracasei CIDCA 8339 and Lactobacillus kefiri CIDCA 83102 were able to diminish Salmonella invasion to the enterocytes. An antagonistic effect on cytoskeleton disruption elicited by the pathogen was also demonstrated. Our results suggest that both strains isolated from milk kefir could be considered as appropriate probiotic candidates.

Inhibition of enteropathogens adhesion to human enterocyte-like HT-29 cells by a dairy strain of Propionibacterium acidipropionici

Adhesion to the host intestinal mucosa is considered relevant for orally delivered probiotics as it prolongs their persistence in the gut and their health promoting effects. Classical propionibacteria are microorganisms of interest due to their role as dairy starters as well as for their functions as probiotics. Propionibacterium acidipropionici Q4, is a dairy strain isolated from a Swiss-type cheese made in Argentina that displays probiotic potential. In the present work we assessed the ability of this strain to adhere to the human enterocyte-like HT-29 cell line and to counteract the adhesion of two common human enteropathogens, such as Escherichia coli C3 and Salmonella Enteritidis 90/390. The results were compared with those obtained with the well-known probiotic Lactobacillus rhamnosus GG. P. acidipropionici Q4 showed a high adhesion capacity, even higher than the reference strain L. rhamnosus GG (42.3±4.4% and 36.2±2.3%, respectively), whereas adhesion of enteropathogens was significantly lower (25.2±2.2% for E. coli and 21.0±3.4% for S. Enteritidis). Propionibacteria as well as lactobacilli were able to inhibit by exclusion and competition the adherence of E. coli C3 and S. Enteritidis 90/390 whereas only L. rhamnosus GG displaced S. Enteritidis from HT-29 intestinal cells. Inhibition of pathogens by propionibacteria was not exerted by antimicrobials or coaggregation but was mainly due to exclusion by cell surface components, such as proteins and carbohydrates. The relevance of cell surface proteins (CSP) for preventing pathogens infection was confirmed by their concentration dependent effect observed for both pathogens: 100 µg/ml of CSP inhibited E. coli attachment almost as untreated propionibacteria, whereas it partially inhibited the attachment of S. Enteritidis. Results suggest that P. acidipropionici Q4 could be considered for the development of propionibacteria containing functional foods helpful in counteracting enteropathogen infection.

Secreted Compounds of the Probiotic Bacillus clausii Strain O/C Inhibit the Cytotoxic Effects Induced by Clostridium difficile and Bacillus cereus Toxins

Although the use of probiotics based on Bacillus strains to fight off intestinal pathogens and antibiotic-associated diarrhea is widespread, the mechanisms involved in producing their beneficial effects remain unclear. Here, we studied the ability of compounds secreted by the probiotic Bacillus clausii strain O/C to counteract the cytotoxic effects induced by toxins of two pathogens, Clostridium difficile and Bacillus cereus, by evaluating eukaryotic cell viability and expression of selected genes. Coincubation of C. difficile and B. cereus toxic culture supernatants with the B. clausii supernatant completely prevented the damage induced by toxins in Vero and Caco-2 cells. The hemolytic effect of B. cereus was also avoided by the probiotic supernatant. Moreover, in these cells, the expression of rhoB, encoding a Rho GTPase target for C. difficile toxins, was normalized when C. difficile supernatant was pretreated using the B. clausii supernatant. All of the beneficial effects observed with the probiotic were abolished by the serine protease inhibitor phenylmethylsulfonyl fluoride (PMSF). Suspecting the involvement of a secreted protease in this protective effect, a protease was purified from the B. clausii supernatant and identified as a serine protease (M-protease; GenBank accession number Q99405). Experiments on Vero cells demonstrated the antitoxic activity of the purified protease against pathogen supernatants. This is the first report showing the capacity of a protease secreted by probiotic bacteria to inhibit the cytotoxic effects of toxinogenic C. difficile and B. cereus strains. This extracellular compound could be responsible, at least in part, for the protective effects observed for this human probiotic in antibiotic-associated diarrhea.