In vitro fermentation of lactulose by human gut bacteria

Fecal fermentation behaviors of Konjac glucomannan and its impacts on human gut microbiota

Dietary fiber targets the regulation of the intestinal flora and thus affects host health, however, the complex relationship between these factors lacks direct evidence. In this study, the regulatory effects of Konjac glucomannan (KGM) on key metabolites of host intestinal flora were examined by using in vitro fermentation. The results showed that KGM could be utilized by the intestinal flora, which inhibited the relative abundance of Paeniclostridium, Lachnoclostridium, Phascolarctobacterium, and Bacteroides and enriched the relative abundance of Desulfovibrio, Sutterella, etc. Fermentation is accompanied by the production of short-chain acids, including acetic and propionic acids. Metabolomics revealed that KGM significantly promoted amino acid metabolism, lipid metabolism, and the biosynthesis of other secondary metabolites. Correlation analysis results showed that the increase of panose and N-(1-carboxy-3-carboxanilidopropyl) alanylproline content was positively correlated with the relative abundance of Megamonas. These results provide evidence that KGM affects host health by regulating gut microbiota and its metabolites.

Raffinose catabolism enhances maize waterlogging tolerance by stimulating adventitious root growth and development

Raffinose mitigates plant heat, drought, and cold stresses; however, whether raffinose contributes to plant waterlogging tolerance is unknown. The maize raffinose synthase mutant zmrafs-1 had seedlings that lack raffinose, generated fewer and shorter adventitious roots, and were more sensitive to waterlogging stress, while overexpression of the raffinose synthase gene, ZmRAFS, increased raffinose content, stimulated adventitious root formation, and enhanced waterlogging tolerance of maize seedlings. Transcriptome analysis of null segregant seedlings compared with zmrafs-1, particularly when waterlogged, revealed that the expression of genes related to galactose metabolism and the auxin biosynthetic pathway were up-regulated by raffinose. Additionally, indole-3-acetic acid content was significantly decreased in zmrafs-1 seedlings and increased in ZmRAFS-overexpressing seedlings. Inhibition of the hydrolysis of raffinose by 1-deoxygalactonojirimycin decreased the waterlogging tolerance of maize seedlings, the expression of genes encoding proteins related to auxin transport-related genes, and the indole-3-acetic acid level in the seedlings, indicating that the hydrolysis of raffinose is necessary for maize waterlogging tolerance. These data demonstrate that raffinose catabolism stimulates adventitious root formation via the auxin signaling pathway to enhance maize waterlogging tolerance.

Food carbohydrates in the gut: structural diversity, microbial utilization, and analytical strategies

Carbohydrates, which are a vital dietary component, undergo digestion and gut fermentation through microbial enzymes to produce beneficial short-chain fatty acids. Certain carbohydrates selectively modulate the gut microbiota, impacting host health. Carbohydrate-active enzymes within the gut microbiota significantly contribute to carbohydrate utilization and microbial diversity. Despite their importance, the structural complexity of carbohydrates poses analytical challenges. However, recent advancements, notably, mass spectrometry, have allowed for their characterization and functional analysis. This review examines the intricate relationship between dietary carbohydrates and the gut microbiota, highlighting the crucial role of advanced analytical techniques in understanding their diversity and implications. These advancements provide valuable insights into carbohydrate bioactivity. Integrating high-throughput analysis with next-generation sequencing provides deeper insights into gut microbial interactions, potentially revealing which carbohydrate structures are beneficial for gut health.

Bifidobacterium adolescentis CCFM1285 combined with yeast β-glucan alleviates the gut microbiota and metabolic disturbances in mice with antibiotic-associated diarrhea

Antibiotic-associated diarrhea (AAD) is a self-limiting condition that can occur during antibiotic therapy. Our previous studies have found that a combination of Bacteroides uniformis and Bifidobacterium adolescentis can effectively alleviate AAD. However, the use of B. uniformis is still strictly limited. Therefore, this study attempted to use yeast β-glucan to enrich the abundance of B. uniformis in the intestine and supplement Bifidobacterium adolescentis to exert a synergistic effect. The lincomycin hydrochloride-induced AAD model was administered yeast β-glucan or a mixture of B. adolescentis CCFM1285 by gavage for one week. Subsequently, changes in the colonic histopathological structure, inflammatory factors, intestinal epithelial permeability and integrity, metabolites, and gut microbiota diversity were assessed. We found that yeast β-glucan, alone or in combination with B. adolescentis CCFM1285, can help attenuate systemic inflammation, increase the rate of tissue structural recovery, regulate metabolism, and restore the gut microbiota. Specifically, the combination of yeast β-glucan and B. adolescentis CCFM1285 was more effective in decreasing interleukin-6 levels, improving pathological changes in the colon, and upregulating occludin expression. Therefore, our study showed that the combination of yeast β-glucan and B. adolescentis CCFM1285 is an efficacious treatment for AAD.

Microbial metabolism marvels: a comprehensive review of microbial drug transformation capabilities

This comprehensive review elucidates the pivotal role of microbes in drug metabolism, synthesizing insights from an exhaustive analysis of over two hundred papers. Employing a structural classification system grounded in drug atom involvement, the review categorizes the microbiome-mediated drug-metabolizing capabilities of over 80 drugs. Additionally, it compiles pharmacodynamic and enzymatic details related to these reactions, striving to include information on encoding genes and specific involved microorganisms. Bridging biochemistry, pharmacology, genetics, and microbiology, this review not only serves to consolidate diverse research fields but also highlights the potential impact of microbial drug metabolism on future drug design and in silico studies. With a visionary outlook, it also lays the groundwork for personalized medicine interventions, emphasizing the importance of interdisciplinary collaboration for advancing drug development and enhancing therapeutic strategies.

Lactobacillus plantarum Generate Electricity through Flavin Mononucleotide-Mediated Extracellular Electron Transfer to Upregulate Epithelial Type I Collagen Expression and Thereby Promote Microbial Adhesion to Intestine

The mechanism behind how flavin mononucleotide (FMN)-producing bacteria attach to a host intestine remains unclear. In order to address this issue, this study isolated the Gram-positive bacteria Lactobacillus plantarum from Mongolian fermented Airag, named L. plantarum MA. These bacteria were further employed as the model microbes, and their electrogenic properties were first identified by their significant expression of type II NADH-quinone oxidoreductase. This study also demonstrated that the electrical activity of L. plantarum MA can be conducted through flavin mononucleotide (FMN)-based extracellular electron transfer, which is highly dependent on the presence of a carbon source in the medium. Our data show that approximately 15 µM of FMN, one of the key electron donors for the generation of electricity, can be produced from L. plantarum MA, as they were cultured in the presence of lactulose for 24 h. We further demonstrated that the electrical activity of L. plantarum MA can promote microbial adhesion and can thus enhance the colonization effectiveness of Caco-2 cells and mouse cecum. Such enhanced adhesiveness was attributed to the increased expression of type I collagens in the intestinal epithelium after treatment with L. plantarum MA. This study reveals the mechanism behind the electrogenic activity of L. plantarum MA and shows how the bacteria utilize electricity to modulate the protein expression of gut tissue for an enhanced adhesion process.

Lactulose in combination with soybean lecithin has a cryoprotective effect on probiotic taxa of bifidobacteria and Lactobacillaceae

Lactulose is commonly used in pharmacy for constipation and hepatic encephalopathy treatment. The prebiotic effect of lactulose is also often mentioned. However, its cryoprotective effect in combination with lecithin on the main representatives of probiotics has not been tested yet. The 12 taxa of bifidobacteria and Lactobacillaceae members were used for the purpose. These were mixed in a ratio of 1:1 with lactulose + lecithin (finally 5.0% and 1.25%, respectively; LL). The 25% glycerol (G+) solution and cultures themselves were applied as positive and negative controls, respectively. Bacterial suspensions were stored at a mild freezing temperature (-20°C) until the end of the experiment (210th day). The LL solution had a comparable (insignificant difference at the P-value = 0.05) cryoprotective effect as the positive control in five of six bifidobacteria and in three of six representatives of Lactobacillaceae. The better cryoprotective effect was revealed in other Lactobacillaceae. At the end of the experiment, the generally accepted therapeutic minimum (>107 Colony Forming Units/mL) was determined in LL solution in five bifidobacteria and four Lactobacillaceae strains. The presented results improve knowledge about long-term mild cryopreservation of the most commonly used probiotics and could contribute to developing new forms of (nutri)synbiotics.

Hydrolysates containing xylooligosaccharides produced by different strategies: Structural characterization, antioxidant and prebiotic activities

This study explores the structural characterization, antioxidant and prebiotic activities of hydrolysates containing xylooligosaccharides (XOS) produced by different strategies: direct fermentation of beechwood xylan (FermBX) and enzymatic treatment of beechwood (EnzBX) and rice husk (EnzRH) xylans. EnzBX and EnzRH showed XOS with a backbone of (1 → 4)-linked-xylopyranosyl residues and branches of arabinose, galactose, and uronic acids. FermBX presented the highest content of total phenolic compounds (14 mg GAE/g) and flavonoids (0.6 mg QE/g), which may contribute to its antioxidant capacity -39.1 μmol TE/g (DPPH), 45.7 μmol TE/g (ABTS), and 79.9 μmol Fe II/g (FRAP). The fermentation of hydrolysates decreased the abundance of microorganisms associated with intestinal diseases from Eubacteriales, Desulfovibrionales and Methanobacteriales orders, while stimulating the growth of organisms belonging to Bacteroides, Megamonas and Limosilactobacillus genera. The production of short-chain fatty acids, ammonia, and CO₂ suggested the prebiotic potential. In conclusion, hydrolysates without previous purification and obtained from non-chemical approaches demonstrated promising biological activities for further food applications.

Raffinose Family Oligosaccharides: Friend or Foe for Human and Plant Health?

Raffinose family oligosaccharides (RFOs) are widespread across the plant kingdom, and their concentrations are related to the environment, genotype, and harvest time. RFOs are known to carry out many functions in plants and humans. In this paper, we provide a comprehensive review of RFOs, including their beneficial and anti-nutritional properties. RFOs are considered anti-nutritional factors since they cause flatulence in humans and animals. Flatulence is the single most important factor that deters consumption and utilization of legumes in human and animal diets. In plants, RFOs have been reported to impart tolerance to heat, drought, cold, salinity, and disease resistance besides regulating seed germination, vigor, and longevity. In humans, RFOs have beneficial effects in the large intestine and have shown prebiotic potential by promoting the growth of beneficial bacteria reducing pathogens and putrefactive bacteria present in the colon. In addition to their prebiotic potential, RFOs have many other biological functions in humans and animals, such as anti-allergic, anti-obesity, anti-diabetic, prevention of non-alcoholic fatty liver disease, and cryoprotection. The wide-ranging applications of RFOs make them useful in food, feed, cosmetics, health, pharmaceuticals, and plant stress tolerance; therefore, we review the composition and diversity of RFOs, describe the metabolism and genetics of RFOs, evaluate their role in plant and human health, with a primary focus in grain legumes.

Lactulose Modulates the Structure of Gut Microbiota and Alleviates Colitis-Associated Tumorigenesis

Lactulose, a galactose-fructose disaccharide, is made from the milk sugar lactose by heating or isomerization processes. Lactulose is proposed to modulate gut microbiota and thus expected to be beneficial in treating inflammatory bowel disease. In the present study, we investigated the therapeutic effect of lactulose on gastrointestinal inflammation and inflammation-related tumorigenesis in a mouse model of colorectal cancer as well as its effect on gut microbiota composition. Azoxymethane (AOM)/dextran sulfate sodium (DSS) model was used in this study. Lactulose treatment was performed by feeding 2% lactulose for 14 weeks. Stool samples collected at 4 time points were used for metagenomic analysis of the microbiota. Pathological analysis was performed 21 weeks after AOM injection. AOM/DSS increased the macrophage counts, inflammatory cytokine expression, colorectal tumorigenesis, and imbalance in gut microbiota composition, as evidenced by increased pathogen abundance (e.g., Escherichia and Clostridium). Lactulose significantly inhibited the inflammatory events, and ameliorated inflammation and tumorigenesis. The composition of the intestinal microbiota was also restored upon lactulose treatment, and lactulose reduced pathogen abundance and increased the abundance of Muribaculum and Lachnospiraceae. Meanwhile, the pathways related to Crohn’s disease were downregulated after lactulose treatment. Our findings suggest that lactulose restores the structure and composition of the intestinal microbiota, mitigates inflammation, and suppresses inflammatory tumorigenesis.

Lactulose significantly increased the relative abundance of Bifidobacterium and Blautia in mice feces as revealed by 16S rRNA amplicon sequencing

BACKGROUND

Lactulose was one of the earliest prebiotics to be identified. To assess the potential risk of large intakes of lactulose to the intestinal microbiota, mice were fed a diet containing lactulose (0%, 5% and 15%, w/w) for 2 weeks and the changes in the fecal microbiota were evaluated by 16S rRNA high-throughput sequencing.

RESULTS

Lactulose intervention decreased the α-diversity of the fecal microbiota in both low-dose and high-dose groups. The relative abundance of Actinobacteria was significantly increased, while that of Bacteroidetes was significantly decreased after lactulose intervention. At the genus level, the relative abundance of Bifidobacterium belonging to Actinobacteria was significantly increased, and that of Alistipes belonging to Bacteroidetes was decreased in both low-dose and high-dose groups. The relative abundance of Blautia was significantly increased from 0.2% to 7.9% in the high-dose group and one strain of Blautia producta was isolated from the mice feces. However, the strain could not utilize lactulose.

CONCLUSION

Overall, the microbial diversity was decreased after lactulose treatment, with significant increases in the relative abundance of Bifidobacterium. We also provide a strategy to increase the relative abundance of Blautia in the intestine by lactulose feeding at high doses, although the mechanism is not revealed. This will help us understand the prebiotic effect of lactulose on the host health. © 2021 Society of Chemical Industry.

Prebiotic Lactulose Ameliorates the Cognitive Deficit in Alzheimer's Disease Mouse Model through Macroautophagy and Chaperone-Mediated Autophagy Pathways

Lactulose, as a prebiotic, can be utilized by human gut microbiota and stimulate their growth. Although microbiota modulation has become an emerging approach to manage many diseases and can be achieved by the administration of prebiotics, fewer investigations have been carried out on the therapeutic mechanism of lactulose. Two trehalose analogs, lactulose and melibiose, were identified as having a neuroprotective effect in polyglutamine and Parkinson disease models. In this study, we examined lactulose and melibiose in a mouse primary hippocampal neuronal culture under the toxicity of oligomeric Aβ_25-35. Lactulose was further tested in vivo because its effective concentration is lower than that of melibiose. Lactulose and trehalose were applied individually to mice before a bilateral intrahippocampal CA1 injection of oligomeric Aβ_25-35. The administration of lactulose and trehalose attenuated the short-term memory and the learning retrieval of Alzheimer's disease (AD) mice. From a pathological analysis, we found that the pretreatment of lactulose and trehalose decreased neuroinflammation and increased the levels of the autophagic pathways. These results suggest that the neuroprotective effects of both lactulose and trehalose are achieved through anti-inflammation and autophagy. In addition, lactulose was better than trehalose in the enhancement of the synaptic protein expression level in AD mice. Therefore, lactulose could potentially be developed into a preventive and/or therapeutic disaccharide for AD.

Comparative Genomic Analysis of Lactiplantibacillus plantarum Isolated from Different Niches

Lactiplantibacillus plantarum can adapt to a variety of niches and is widely distributed in many sources. We used comparative genomics to explore the differences in the genome and in the physiological characteristics of L. plantarum isolated from pickles, fermented sauce, and human feces. The relationships between genotypes and phenotypes were analyzed to address the effects of isolation source on the genetic variation of L. plantarum. The comparative genomic results indicate that the numbers of unique genes in the different strains were niche-dependent. L. plantarum isolated from fecal sources generally had more strain-specific genes than L. plantarum isolated from pickles. The phylogenetic tree and average nucleotide identity (ANI) results indicate that L. plantarum in pickles and fermented sauce clustered independently, whereas the fecal L. plantarum was distributed more uniformly in the phylogenetic tree. The pan-genome curve indicated that the L. plantarum exhibited high genomic diversity. Based on the analysis of the carbohydrate active enzyme and carbohydrate-use abilities, we found that L. plantarum strains isolated from different sources exhibited different expression of the Glycoside Hydrolases (GH) and Glycosyl Transferases (GT) families and that the expression patterns of carbohydrate active enzymes were consistent with the evolution relationships of the strains. L. plantarum strains exhibited niche-specific characteristicsand the results provided better understating on genetics of this species.

Selective Utilization of the Human Milk Oligosaccharides 2'-Fucosyllactose, 3-Fucosyllactose, and Difucosyllactose by Various Probiotic and Pathogenic Bacteria

Prebiotic human milk oligosaccharides (HMOs) are found in human milk, which are not digested by infants but are metabolized by beneficial gut bacteria. We determined the ability of 57 bacterial strains within the Family Lactobacillaceae and genera Bifidobacterium and Bacteroides and potentially pathogenic bacteria to ferment the HMOs 2'-fucosyllactose, 3-fucosyllactose, and difucosyllactose. In addition, prebiotic galacto-oligosaccharides (GOS), lactose, fucose, and glucose were evaluated as carbon sources for these bacterial strains. Bacterial growth was monitored using the automatic Bioscreen C system. Only certain bifidobacteria, such as Bifidobacterium longum subsp. infantis and Bifidobacterium bifidum, as well as Bacteroides fragilis, Bacteroides vulgatus, and Bacteroides thetaiotaomicron utilized the studied HMOs as their sole carbon source, whereas almost all studied bacterial strains were able to utilize GOS, lactose, and glucose. The selectivity in utilization of HMOs by only certain bacteria can be advantageous by promoting beneficial microbes but not supporting the harmful pathogens in contrast to other less selective prebiotics.

Genes Involved in Galactooligosaccharide Metabolism in Lactobacillus reuteri and Their Ecological Role in the Gastrointestinal Tract

Strains of Lactobacillus reuteri are commonly used as probiotics due to their demonstrated therapeutic properties. Many strains of L. reuteri also utilize the prebiotic galactooligosaccharide (GOS), providing a basis for formulating synergistic synbiotics that could enhance growth or persistence of this organism in vivo In this study, in-frame deletion mutants were constructed to characterize the molecular basis of GOS utilization in L. reuteri ATCC PTA-6475. Results suggested that GOS transport relies on a permease encoded by lacS, while a second unidentified protein may function as a galactoside transporter. Two β-galactosidases, encoded by lacA and lacLM, sequentially degrade GOS oligosaccharides and GOS disaccharides, respectively. Inactivation of lacL and lacM resulted in impaired growth in the presence of GOS and lactose. In vitro competition experiments between the wild-type and ΔlacS ΔlacM strains revealed that the GOS-utilizing genes conferred a selective advantage in media with GOS but not glucose. GOS also provided an advantage to the wild-type strain in experiments in gnotobiotic mice but only on a purified, no sucrose diet. Differences in cell numbers between GOS-fed mice and mice that did not receive GOS were small, suggesting that carbohydrates other than GOS were sufficient to support growth. On a complex diet, the ΔlacS ΔlacM strain was outcompeted by the wild-type strain in gnotobiotic mice, suggesting that lacL and lacM are involved in the utilization of alternative dietary carbohydrates. Indeed, the growth of the mutants was impaired in raffinose and stachyose, which are common in plants, demonstrating that α-galactosides may constitute alternate substrates of the GOS pathway.IMPORTANCE This study shows that lac genes in Lactobacillus reuteri encode hydrolases and transporters that are necessary for the metabolism of GOS, as well as α-galactoside substrates. Coculture experiments with the wild-type strain and a gos mutant clearly demonstrated that GOS utilization confers a growth advantage in medium containing GOS as the sole carbohydrate source. However, the wild-type strain also outcompeted the mutant in germfree mice, suggesting that GOS genes in L. reuteri also provide a basis for utilization of other carbohydrates, including α-galactosides, ordinarily present in the diets of humans and other animals. Collectively, our work provides information on the metabolism of L. reuteri in its natural niche in the gut and may provide a basis for the development of synbiotic strategies.

Lactulose: Patient- and dose-dependent prebiotic properties in humans

Lactulose is a disaccharide used in clinical practice since 1957 and has since been tested in the treatment of many human disorders, including chronic constipation, hepatic encephalopathy, and chronic kidney disease. Its mode of action is based on the lactulose fermentation by intestinal microbiota. Based on in silico, in vitro and in vivo studies we comprehensively review here the impact of lactulose on human gut/fecal and vaginal microbiota composition and both fecal and blood metabolomes. However, both in vitro and in vivo studies summarized in this review have revealed that the effects of lactulose on human microbiota composition are both patient- and dose-dependent. This highlights the need of heterogeneity indication in clinical trials.

Pharmacomicrobiomics: The Holy Grail to Variability in Drug Response?

The human body, with 3.0 × 10¹³ cells and more than 3.8 × 10¹³ microorganisms, has nearly a one-to-one ratio of resident microbes to human cells. Initiatives like the Human Microbiome Project, American Gut, and Flemish Gut have identified associations between microbial taxa and human health. The study of interactions between microbiome and pharmaceutical agents, i.e., pharmacomicrobiomics, has revealed an instrumental role of the microbiome in modulating drug response that alters the therapeutic outcomes. In this review, we present our current comprehension of the relationship of the microbiome, host biology, and pharmaceutical agents such as cardiovascular drugs, analgesics, and chemotherapeutic agents to human disease and treatment outcomes. We also discuss the significance of studying diet-gene-drug interactions and further address the key challenges associated with pharmacomicrobiomics. Finally, we examine proposed models employing systems biology for the application of pharmacomicrobiomics and other -omics data, and provide approaches to elucidate microbiome-drug interactions to improve future translation to personalized medicine.

In vitro fermentation of raffinose by the human gut bacteria

Raffinose has become a major focus of research interest and recent studies have shown that besides beneficial bifidobacteria and lactobacilli, Escherichia coli, Enterococcus faecium and Streptococcus pneumoniae can also utilize raffinose and raffinose might lead to flatulence in some hosts. Therefore, it is required to find out the raffinose-metabolizing bacteria in the gut and the bacteria responsible for the flatulence. The BLASTP search results showed that the homologous proteins of glycosidases related to raffinose utilization are widely distributed in 196 of the 528 gut bacterial strains. Fifty-nine bacterial strains belonging to nine species of five genera were isolated from human feces and were found to be capable of utilizing raffinose; of these species, Enterococcus avium and Streptococcus salivarius were reported for the first time. High-performance liquid chromatography (HPLC) analysis of the supernatants of the nine species revealed that the bacteria could utilize raffinose in different manners. Glucose and melibiose were detected in the supernatants of Enterococcus avium E5 and Streptococcus salivarius B5, respectively. However, no resulting saccharides of raffinose degradation were detected in the supernatants of other seven strains, indicating that they had different raffinose utilization types from Enterococcus avium E5 and Streptococcus salivarius B5. Gas was produced with raffinose utilization by Escherichia coli, Enterococcus faecium, Streptococcus macedonicus, Streptococcus pasteurianus and Enterococcus avium. Thus, more attention should be paid to the raffinose-utilizing bacteria besides bifidobacteria and further studies are required to reveal the mechanisms of raffinose utilization to clarify the relationship between raffinose and gut bacteria.

First Insights into the Gut Microbiota of Mexican Patients with Celiac Disease and Non-Celiac Gluten Sensitivity

Gluten-related disorders (GRDs) are common chronic enteropathies and increasing evidence suggests an involvement of the gut microbiota. We examined the gut microbiota in Mexican people afflicted with GRDs. Ultra-high-throughput 16S marker sequencing was used to deeply describe the duodenal and fecal microbiota of patients with celiac disease (CD, n = 6), non-celiac gluten sensitivity (NCGS, n = 12), and healthy subjects (n = 12) from our local area. Additionally, we also investigated the changes in gut microbiota after four weeks on a gluten-free diet (GFD) in a subset of patients from whom paired samples were available. Despite a high inter-individual variability, significant differences in various microbial populations were identified. The linear discriminant analysis (LDA) effect size (LEfSe) method revealed that the genus Actinobacillus and the family Ruminococcaceae were higher in the duodenal and fecal microbiota of NCGS patients, respectively, while Novispirillum was higher in the duodenum of CD patients (p < 0.05, LDA score > 3.5). Interestingly, paired samples from NCGS patients showed a significant difference in duodenal Pseudomonas between the baseline period (median: 1.3%; min/max: 0.47⁻6.8%) and the period after four weeks on GFD (14.8%; 2.3⁻38.5%, p < 0.01, Wilcoxon signed-rank test). These results encourage more research on GRDs in México.

Microbiota stability in healthy individuals after single-dose lactulose challenge-A randomized controlled study

BACKGROUND AND AIMS

Lactulose is a common food ingredient and widely used as a treatment for constipation or hepatic encephalopathy and a substrate for hydrogen breath tests. Lactulose is fermented by the colon microbiota resulting in the production of hydrogen (H2). H2 is a substrate for enteropathogens including Salmonella Typhimurium (S. Typhimurium) and increased H2 production upon lactulose ingestion might favor the growth of H2-consuming enteropathogens. We aimed to analyze effects of single-dose lactulose ingestion on the growth of intrinsic Escherichia coli (E. coli), which can be efficiently quantified by plating and which share most metabolic requirements with S. Typhimurium.

METHODS

32 healthy volunteers (18 females, 14 males) were recruited. Participants were randomized for single-dose ingestion of 50 g lactulose or 50 g sucrose (controls). After ingestion, H2 in expiratory air and symptoms were recorded. Stool samples were acquired at days -1, 1 and 14. We analyzed 16S microbiota composition and abundance and characteristics of E. coli isolates.

RESULTS

Lactulose ingestion resulted in diarrhea in 14/17 individuals. In 14/17 individuals, H2-levels in expiratory air increased by ≥20 ppm within 3 hours after lactulose challenge. H2-levels correlated with the number of defecations within 6 hours. E. coli was detectable in feces of all subjects (2 x 10(2)-10(9) CFU/g). However, the number of E. coli colony forming units (CFU) on selective media did not differ between any time point before or after challenge with sucrose or lactulose. The microbiota composition also remained stable upon lactulose exposure.

CONCLUSION

Ingestion of a single dose of 50 g lactulose does not significantly alter E. coli density in stool samples of healthy volunteers. 50 g lactulose therefore seems unlikely to sufficiently alter growth conditions in the intestine for a significant predisposition to infection with H2-consuming enteropathogens such as S. Typhimurium (www.clinicaltrials.gov NCT02397512).

Promising Prebiotic Candidate Established by Evaluation of Lactitol, Lactulose, Raffinose, and Oligofructose for Maintenance of a Lactobacillus-Dominated Vaginal Microbiota

Perturbations to the vaginal microbiota can lead to dysbiosis, including bacterial vaginosis (BV), which affects a large portion of the female population. In a healthy state, the vaginal microbiota is characterized by low diversity and colonization by Lactobacillus spp., whereas in BV, these species are displaced by a highly diverse population of bacteria associated with adverse vaginal health outcomes. Since prebiotic ingestion has been a highly effective approach to invigorate lactobacilli for improved intestinal health, we hypothesized that these compounds could stimulate lactobacilli at the expense of BV organisms to maintain vaginal health. Monocultures of commensal Lactobacillus crispatus, Lactobacillus vaginalis, Lactobacillus gasseri, Lactobacillus johnsonii, Lactobacillus jensenii, and Lactobacillus iners, in addition to BV-associated organisms and Candida albicans, were tested for their ability to utilize a representative group of prebiotics consisting of lactitol, lactulose, raffinose, and oligofructose. The disaccharide lactulose was found to most broadly and specifically stimulate vaginal lactobacilli, including the strongly health-associated species L. crispatus, and importantly, not to stimulate BV organisms or C. albicans. Using freshly collected vaginal samples, we showed that exposure to lactulose promoted commensal Lactobacillus growth and dominance and resulted in healthy acidity partially through lactic acid production. This provides support for further testing of lactulose to prevent dysbiosis and potentially to reduce the need for antimicrobial agents in managing vaginal health.

IMPORTANCE Bacterial vaginosis (BV) and other dysbioses of the vaginal microbiota significantly affect the quality of life of millions of women. Antimicrobial therapy is often poorly effective, causes side effects, and does not prevent recurrences. We report one of very few studies that have evaluated how prebiotics—compounds that are selectively fermented by beneficial bacteria such as Lactobacillus spp.—can modulate the vaginal microbiota. We also report use of a novel in vitro polymicrobial model to study the impact of prebiotics on the vaginal microbiota. The identification of prebiotic lactulose as enhancing Lactobacillus growth but not that of BV organisms or Candida albicans has direct application for retention of homeostasis and prevention of vaginal dysbiosis and infection.

Prebiotics and synbiotics in ulcerative colitis

BACKGROUND

Ulcerative colitis (UC) is a chronic inflammatory disease of the colon with unclear pathogenesis. A dysbiotic intestinal microbiota is regarded as a key component in the disease process and there has been significant interest in developing new treatments which target the microbiota.

AIM

To give an overview of the studies to date investigating prebiotics and synbiotics for the treatment of UC.

METHODS

A literature search of PubMed and related search engines was carried out using the terms "ulcerative colitis" in combination with "prebiotic", "synbiotic" or "dietary fibre".

RESULTS

In total 17 studies on humans examining the effect of prebiotics in UC were found. Five major groups could be distinguished. Fructo-oligosaccharides were tried in six studies (mean 35 patients included, range 9-121). One study found a clinical response while two demonstrated indirect evidence of an effect. Germinated barley foodstuff was used in 8 studies (mean 38 patients, range 10-63). One study found an endoscopic response, while four noted a clinical response and two some indirect effects. Galacto-oligosaccharides, lactulose and resveratrol were used in one study each (mean 48 patients, range 41-52). One study found an endoscopic response and one a clinical response.

CONCLUSION

There is yet inadequate evidence - especially in humans - to support any particular prebiotic in the clinical management of UC. However, due to the bulk of evidence supporting the effect of the microbiota on colonic inflammation, there is enough potential to justify further high-quality clinical trials investigating this subject.

Lactulose Differently Modulates the Composition of Luminal and Mucosal Microbiota in C57BL/6J Mice

In this study, C57BL/6J mice were fed diets supplemented with different proportions of lactulose (0%, 5%, and 15%) for 2 weeks to study its effects on the luminal and mucosal microbiota. The luminal and mucosal samples of cecum and colon were investigated. After high-lactulose treatment (15%), pH of the luminal contents decreased from 6.90-7.72 to 5.95-6.21 from the cecum to distal colon, and the amount of total short-chain fatty acids in the cecum was significantly increased. The luminal content was mostly dominated by Firmicutes, Actinobacteria, and Bacteroidetes, while the mucus was dominated by Firmicutes, Proteobacteria, and Bacteroidetes. The abundance of Actinobacteria was significantly increased in the content, and Proteobacteria was the most abundant phylum (∼50%) in the mucus after high-lactulose treatment. At the genus level, Bifidobacterium and Akkermansia were both significantly increased in the content, and Helicobacter was the most abundant in the mucus.

Revealing the combined effects of lactulose and probiotic enterococci on the swine faecal microbiota using 454 pyrosequencing

Demand for the development of non‐antibiotic growth promoters in animal production has increased in recent years. This report compared the faecal microbiota of weaned piglets under the administration of a basal diet (CON) or that containing prebiotic lactulose (LAC), probiotic Enterococcus faecium NCIMB 11181 (PRO) or their synbiotic combination (SYN). At the phylum level, the Firmicutes to Bacteroidetes ratio increased in the treatment groups compared with the CON group, and the lowest proportion of Proteobacteria was observed in the LAC group. At the family level, Enterobacteriaceae decreased in all treatments; more than a 10‐fold reduction was observed in the LAC (0.99%) group compared with the CON group. At the genus level, the highest Oscillibacter proportion was detected in PRO, the highest Clostridium in LAC and the highest Lactobacillus in SYN; the abundance of Escherichia was lowest in the LAC group. Clustering in the discriminant analysis of principal components revealed distinct separation of the feeding groups (CON, LAC, PRO and SYN), showing different microbial compositions according to different feed additives or their combination. These results suggest that individual materials and their combination have unique actions and independent mechanisms for changes in the distal gut microbiota.

First evidence of polar flagella in Klebsiella pneumoniae isolated from a patient with neonatal sepsis

The genus Klebsiella belongs to the family Enterobacteriaceae, and is currently considered to be non-motile and non-flagellated. In the present work, 25 Klebsiella strains isolated from nosocomial infections were assessed for motility under different growth conditions. One Klebsiella isolate, KpBUAP021, demonstrated a swim-like motility phenotype. The K. pneumoniae genotype was confirmed by 16S rRNA and rpoB gene sequence analysis. Multilocus sequence typing analysis also revealed that the KpBUAP021 strain places it in the ST345 sequence type, and belongs to the phylogenetic Kpl group. Transmission electron microscopy and the Ryu staining technique revealed that KpBUAP021 expresses polar flagella. Finally, the presence of fliC, fliA and flgH genes in this K. pneumoniae strain was confirmed. This report presents the first evidence for flagella-mediated motility in a K. pneumoniae clinical isolate, and represents an important finding related to its evolution and pathogenic potential.

The influence of gut microbiota on drug metabolism and toxicity

INTRODUCTION

Gut microbiota plays critical roles in drug metabolism. The variation of gut microbiota contributes to the interindividual differences toward drug therapy including drug-induced toxicity and efficacy. Accordingly, the investigation and elucidation of gut microbial impacts on drug metabolism and toxicity will not only facilitate the way of personalized medicine, but also improve rational drug design.

AREAS COVERED

This review provides an overview of the microbiota-host co-metabolism on drug metabolism and summarizes 30 clinical drugs that are co-metabolized by host and gut microbiota. Moreover, this review is specifically focused on elucidating the gut microbial modulation of some clinical drugs, in which the gut microbial influences on drug metabolism, drug-induced toxicity and efficacy are discussed.

EXPERT OPINION

The gut microbial contribution to drug metabolism and toxicity is increasingly recognized, but remains largely unexplored due to the extremely complex relationship between gut microbiota and host. The mechanistic elucidation of gut microbiota in drug metabolism is critical before any practical progress in drug design or personalized medicine could be made by modulating human gut microbiota. Analytical technique innovation is urgently required to strengthen our capability in recognizing microbial functions, including metagenomics, metabolomics and the integration of multidisciplinary knowledge.