Developments in understanding and applying prebiotics in research and practice-an ISAPP conference paper.

AIMS: The concept of using specific dietary components to selectively modulate the gut microbiota to confer a health benefit, defined as prebiotics, originated in 1995. In 2018, a group of scientists met at the International Scientific Association for Probiotics and Prebiotics annual meeting in Singapore to discuss advances in the prebiotic field, focussing on issues affecting functionality, research methodology and geographical differences. METHODS AND RESULTS: The discussion ranged from examining scientific literature supporting the efficacy of established prebiotics, to the prospects for establishing health benefits associated with novel compounds, isolated from different sources. CONCLUSIONS: While many promising candidate prebiotics from across the globe have been highlighted in preliminary research, there are a limited number with both demonstrated mechanism of action and defined health benefits as required to meet the prebiotic definition. Prebiotics are part of a food industry with increasing market sales, yet there are great disparities in regulations in different countries. Identification and commercialization of new prebiotics with unique health benefits means that regulation must improve and remain up-to-date so as not to risk stifling research with potential health benefits for humans and other animals. SIGNIFICANCE AND IMPACT OF STUDY: This summary of the workshop discussions indicates potential avenues for expanding the range of prebiotic substrates, delivery methods to enhance health benefits for the end consumer and guidance to better elucidate their activities in human studies.

Antimicrobial activity of selected synbiotics targeted for the elderly against pathogenic Escherichia coli strains.

The aim of the present study was to evaluate the antimicrobial activity of two synbiotic combinations, Lactobacillus fermentum with short-chain fructooligosaccharides (FOS-LF) and Bifidobacterium longum with isomaltooligosaccharides (IMO-BL), against enterohaemorrhagic Escherichia coli O157:H7 and enteropathogenic E. coli O86. Antimicrobial activity was determined (1) by co-culturing the synbiotics and pathogens in batch cultures, and (2) with the three-stage continuous culture system (gut model), inoculated with faecal slurry from an elderly donor. In the co-culture experiments, IMO-BL was significantly inhibitory to both E. coli strains, while FOS-LF was slightly inhibitory or not inhibitory. Factors other than acid production appeared to play a role in the inhibition. In the gut models, both synbiotics effectively inhibited E. coli O157 in the first vessel, but not in vessels 2 and 3. E. coli O86 was not significantly inhibited.

Effects of single- and multi-strain probiotics on biofilm formation and in vitro adhesion to bladder cells by urinary tract pathogens.

PURPOSE: There is increasing evidence that probiotic bacteria can inhibit and/or prevent urinary tract infections. Possible mechanisms include prevention of adhesion of pathogens to the bladder epithelium and inhibition of biofilm formation. Currently there is interest in the comparative efficacy of single probiotics vs. strain mixtures. We have therefore tested the inhibitory activity of four single probiotics and four probiotic mixtures towards the urinary tract pathogens Escherichia coli NCTC 9001 and Enterococcus faecalis NCTC 00775. METHODS: Inhibition of biofilm formation by cell-free supernatants was tested using the Crystal Violet assay, while prevention of pathogen adhesion to host cells was tested by using bladder cancer cells as a model for the human urinary tract. RESULTS: Under pH-controlled conditions, there was no significant inhibition of biofilm formation by any treatment. Without pH control, 5/8 treatments significantly inhibited biofilm production by E. coli, while 5/8 treatments inhibited production by E. faecalis. Using data from all Crystal Violet assays, there was no significant difference in the ability of single- and multi-strain probiotics to inhibit biofilm formation. In the cell culture assays, all treatments were able to significantly reduce numbers of pathogenic cells adhering to host cells by 2.5-3.5 logs. No significant difference was observed between the displacement caused by single strains and mixtures for either pathogen. CONCLUSIONS: Inhibition of biofilm seems to be a major mechanism of urinary tract pathogen exclusion, related to, and possibly dependent upon, the probiotic ability to reduce environmental pH. Exclusion via competition of binding sites is a possible in vivo mechanism for these probiotics. If an additive or synergistic effect exists between strains within a mixture, it does not manifest itself in a greater effect through these two inhibitory mechanisms.

The type and quantity of dietary fat and carbohydrate alter faecal microbiome and short-chain fatty acid excretion in a metabolic syndrome 'at-risk' population.

INTRODUCTION AND OBJECTIVES: An obese-type human microbiota with an increased Firmicutes:Bacteroidetes ratio has been described that may link the gut microbiome with obesity and metabolic syndrome (MetS) development. Dietary fat and carbohydrate are modifiable risk factors that may impact on MetS by altering the human microbiome composition. We determined the effect of the amount and type of dietary fat and carbohydrate on faecal bacteria and short chain fatty acid (SCFA) concentrations in people 'at risk' of MetS. DESIGN: A total of 88 subjects at increased MetS risk were fed a high saturated fat diet (HS) for 4 weeks (baseline), then randomised onto one of the five experimental diets for 24 weeks: HS; high monounsaturated fat (MUFA)/high glycemic index (GI) (HM/HGI); high MUFA/low GI (HM/LGI); high carbohydrate (CHO)/high GI (HC/HGI); and high CHO/low GI (HC/LGI). Dietary intakes, MetS biomarkers, faecal bacteriology and SCFA concentrations were monitored. RESULTS: High MUFA diets did not affect individual bacterial population numbers but reduced total bacteria and plasma total and LDL-cholesterol. The low fat, HC diets increased faecal Bifidobacterium (P=0.005, for HC/HGI; P=0.052, for HC/LGI) and reduced fasting glucose and cholesterol compared to baseline. HC/HGI also increased faecal Bacteroides (P=0.038), whereas HC/LGI and HS increased Faecalibacterium prausnitzii (P=0.022 for HC/HGI and P=0.018, for HS). Importantly, changes in faecal Bacteroides numbers correlated inversely with body weight (r=-0.64). A total bacteria reduction was observed for high fat diets HM/HGI and HM/LGI (P=0.023 and P=0.005, respectively) and HS increased faecal SCFA concentrations (P<0.01). CONCLUSION: This study provides new evidence from a large-scale dietary intervention study that HC diets, irrespective of GI, can modulate human faecal saccharolytic bacteria, including bacteroides and bifidobacteria. Conversely, high fat diets reduced bacterial numbers, and in the HS diet, increased excretion of SCFA, which may suggest a compensatory mechanism to eliminate excess dietary energy.

Comparative in vitro inhibition of urinary tract pathogens by single- and multi-strain probiotics.

PURPOSE: Multi-species probiotic preparations have been suggested as having a wide spectrum of application, although few studies have compared their efficacy with that of individual component strains at equal concentrations. We therefore tested the ability of 4 single probiotics and 4 probiotic mixtures to inhibit the urinary tract pathogens Escherichia coli NCTC 9001 and Enterococcus faecalis NCTC 00775. METHODS: We used an agar spot test to test the ability of viable cells to inhibit pathogens, while a broth inhibition assay was used to assess inhibition by cell-free probiotic supernatants in both pH-neutralised and non-neutralised forms. RESULTS: In the agar spot test, all probiotic treatments showed inhibition, L. acidophilus was the most inhibitory single strain against E. faecalis, L. fermentum the most inhibitory against E. coli. A commercially available mixture of 14 strains (Bio-Kult(®)) was the most effective mixture, against E. faecalis, the 3-lactobacillus mixture the most inhibitory against E. coli. Mixtures were not significantly more inhibitory than single strains. In the broth inhibition assays, all probiotic supernatants inhibited both pathogens when pH was not controlled, with only 2 treatments causing inhibition at a neutral pH. CONCLUSIONS: Both viable cells of probiotics and supernatants of probiotic cultures were able to inhibit growth of two urinary tract pathogens. Probiotic mixtures prevented the growth of urinary tract pathogens but were not significantly more inhibitory than single strains. Probiotics appear to produce metabolites that are inhibitory towards urinary tract pathogens. Probiotics display potential to reduce the incidence of urinary tract infections via inhibition of colonisation.

Effects of 24-week prebiotic intervention on self-reported upper respiratory symptoms, gastrointestinal symptoms, and markers of immunity in elite rugby union players.

OBJECTIVES: Elite rugby union players face numerous physiological and psychological stressors which can increase upper respiratory and gastrointestinal illness risk, and in turn can compromise training and competitive performance. This study aimed to investigate the effect of daily prebiotic supplementation on upper respiratory symptoms, gastrointestinal symptoms, and markers of immune function in elite rugby union players. METHODS: Thirty-three elite rugby union players were randomly assigned to consume a prebiotic (2.8 g/day galactooligosaccharide) or placebo (2.8 g/day maltodextrin), daily for 168 days under double-blind conditions. Participants completed daily and weekly questionnaires for self-reported upper respiratory and gastrointestinal symptoms respectively. Blood and saliva samples were collected at 0, 84, and 168 days for assessment of plasma TNF-α and CRP, and saliva IgA respectively. RESULTS: The prebiotic group experienced a 2-day reduction in upper respiratory symptom duration (P = 0.045). Gastrointestinal symptom severity and incidence were lower in the prebiotic group compared to the placebo group (P < 0.001, P = 0.041) respectively. Salivary immunoglobulin A secretion rate was 42% greater in the prebiotic group compared to the placebo group at day 168 (P = 0.004), no differences in CRP and TNF-α were found (P > 0.05). CONCLUSION: A 168-day dietary prebiotic intervention reduced the duration of upper respiratory symptoms and reduced the incidence and severity of gastrointestinal symptoms in elite rugby union players. These findings suggest that seasonal prebiotic interventions may be beneficial for reducing illness in elite rugby union players, improving their availability to train and compete.Key pointsElite athletes are susceptible to upper respiratory symptoms and gastrointestinal symptoms which may impact upon training availability and competition performance.For the first time, this study shows that a dietary prebiotic intervention can reduce the duration of upper respiratory symptoms by 2 days in elite rugby union players.Dietary prebiotic supplementation can improve the incidence and severity of gastrointestinal symptoms experienced by elite rugby union players.Prebiotic supplementation was able to increase salivary IgA secretion after 168 days.These findings can inform practice suggesting that seasonal prebiotic use has the potential to modulate immune function and reduce illness in elite rugby union, which may improve a player's availability to train and compete.The mechanisms by which prebiotics reduce URS and GIS require further research exploration.

In vitro evaluation of single- and multi-strain probiotics: Inter-species inhibition between probiotic strains, and inhibition of pathogens.

Many studies comparing the effects of single- and multi-strain probiotics on pathogen inhibition compare treatments with different concentrations. They also do not examine the possibility of inhibition between probiotic strains with a mixture. We tested the ability of 14 single-species probiotics to inhibit each other using a cross-streak assay, and agar spot test. We then tested the ability of 15 single-species probiotics and 5 probiotic mixtures to inhibit Clostridium difficile, Escherichia coli and S. typhimurium, using the agar spot test. Testing was done with mixtures created in two ways: one group contained component species incubated together, the other group of mixtures was made using component species which had been incubated separately, equalised to equal optical density, and then mixed in equal volumes. Inhibition was observed for all combinations of probiotics, suggesting that when used as such there may be inhibition between probiotics, potentially reducing efficacy of the mixture. Significant inter-species variation was seen against each pathogen. When single species were tested against mixtures, the multi-species preparations displayed significantly (p < 0.05 or less) greater inhibition of pathogens in 12 out of 24 cases. Despite evidence that probiotic species will inhibit each other when incubated together in vitro, in many cases a probiotic mixture was more effective at inhibiting pathogens than its component species when tested at approximately equal concentrations of biomass. This suggests that using a probiotic mixture might be more effective at reducing gastrointestinal infections, and that creating a mixture using species with different effects against different pathogens may have a broader spectrum of action that a single provided by a single strain.

Colon extended physiologically based extraction test (CE-PBET) increases bioaccessibility of soil-bound PAH.

Assessment of the risk to human health posed by contaminated land may be seriously overestimated if reliant on total pollutant concentration. In vitro extraction tests, such as the physiologically based extraction test (PBET), imitate the physicochemical conditions of the human gastro-intestinal tract and offer a more practicable alternative for routine testing purposes. However, even though passage through the colon accounts for approximately 80% of the transit time through the human digestive tract and the typical contents of the colon in vivo are a carbohydrate-rich aqueous medium with the potential to promote desorption of organic pollutants, PBET comprises stomach and small intestine compartments only. Through addition of an eight-hour colon compartment to PBET and use of a carbohydrate-rich fed-state medium we demonstrated that colon-extended PBET (CE-PBET) increased assessments of soil-bound PAH bioaccessibility by up to 50% in laboratory soils and a factor of 4 in field soils. We attribute this increased bioaccessibility to a combination of the additional extraction time and the presence of carbohydrates in the colon compartment, both of which favor PAH desorption from soil. We propose that future assessments of the bioaccessibility of organic pollutants in soils using physiologically based extraction tests should have a colon compartment as in CE-PBET.

Health benefits of probiotics: are mixtures more effective than single strains?

PURPOSE: Most studies on probiotics utilise single strains, sometimes incorporated into yoghurts. There are fewer studies on efficacy of mixtures of probiotic strains. This review examines the evidence that (a) probiotic mixtures are beneficial for a range of health-related outcomes and (b) mixtures are more or less effective than their component strains administered separately. RESULTS: Mixtures of probiotics had beneficial effects on the end points including irritable bowel syndrome and gut function, diarrhoea, atopic disease, immune function and respiratory tract infections, gut microbiota modulation, inflammatory bowel disease and treatment of Helicobacter pylori infection. However, only 16 studies compared the effect of a mixture with that of its component strains separately, although in 12 cases (75%), the mixture was more effective. CONCLUSION: Probiotic mixtures appear to be effective against a wide range of end points. Based on a limited number of studies, multi-strain probiotics appear to show greater efficacy than single strains, including strains that are components of the mixtures themselves. However, whether this is due to synergistic interactions between strains or a consequence of the higher probiotic dose used in some studies is at present unclear.

In vitro measurement of the impact of human milk oligosaccharides on the faecal microbiota of weaned formula-fed infants compared to a mixture of prebiotic fructooligosaccharides and galactooligosaccharides.

AIMS: To investigate the impact of human milk oligosaccharides (HMOs) from a single donor (SO), HMOs from multiple donors (PO), a fructooligosaccharides and galactooligosaccharides mixture (FG) on the composition of a batch culture inoculated with faecal microbiota from formula-fed infants. METHODS AND RESULTS: Three substrates were compared using 24-h pH-controlled anaerobic batch cultures inoculated with infant faecal slurries. Changes in bacterial populations, short-chain fatty acids (SCFA) production and bacterial 16S rRNA gene profiles were determined. All three substrates significantly increased numbers of bifidobacteria, bacteroides and those aligning with the clostridial cluster XIVa. Neither the FG nor the HMOs substrates supported the growth of the Clostridium perfringens-histolyticum group. SCFA production corresponded to changes observed in bacterial populations. Denaturing gradient gel electrophoresis fingerprint analysis showed a distinct profile of faecal bacteria present in each infant. CONCLUSIONS: HMOs modulated infant faecal culture composition in a similar manner to the prebiotic mixture FG in vitro. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first demonstration of the impact of pure HMOs on the mixed culture of infant faecal bacteria. HMOs induced the growth of several saccharolytic bacterial groups and may thus play a role in the health-promoting attributes of human breast milk and have an extended significance in infant diet during/after weaning.

Investigation of the faecal microbiota of geriatric cats.

AIMS: Aim of the study was to investigate the faecal microbiota of geriatric cats, as aging affects the nutrient digestibility and metabolic function of the feline intestine. METHODS AND RESULTS: Twenty geriatric cats were randomly assigned to two groups that were fed different foods. Coriobacteriaceae, Clostridium cluster XIV, bifidobacteria and lactic acid bacteria were the dominant faecal bacterial groups, accounting for c. 40% of total bacteria. Clostridium cluster IX was less predominant (0.5% of total bacteria), while the remaining bacterial populations enumerated only accounted for 0.2% of total bacteria. Highly diverse microbial profiles were demonstrated for geriatric cats with denaturing gradient gel electrophoresis, although a few common bands were evident. Some differences were seen in the feline faecal microbiota between animal groups at the same time or over time for individual animals. However, no obvious clustering based on animal group or sample time was indicated. CONCLUSIONS: Geriatric cats harboured a complex faecal microbiota and c. 41% of total bacteria have been detected with the probes employed. SIGNIFICANCE AND IMPACT OF THE STUDY: First molecular-based study examining faecal microbiota of geriatric felines. Knowledge of the microbiota associated with ageing in cats may allow improved development of foods specific for the needs of senior cats.

Response of porcine intestinal in vitro organ culture tissues following exposure to Lactobacillus plantarum JC1 and Salmonella enterica serovar Typhimurium SL1344.

The development of novel intervention strategies for the control of zoonoses caused by bacteria such as Salmonella spp. in livestock requires appropriate experimental models to assess their suitability. Here, a novel porcine intestinal in vitro organ culture (IVOC) model utilizing cell crown (CC) technology (CCIVOC) (Scaffdex) was developed. The CCIVOC model was employed to investigate the characteristics of association of S. enterica serovar Typhimurium strain SL1344 with porcine intestinal tissue following exposure to a Lactobacillus plantarum strain. The association of bacteria to host cells was examined by light microscopy and electron microscopy (EM) after appropriate treatments and staining, while changes in the proteome of porcine jejunal tissues were investigated using quantitative label-free proteomics. Exposure of porcine intestinal mucosal tissues to L. plantarum JC1 did not reduce the numbers of S. Typhimurium bacteria associating to the tissues but was associated with significant (P < 0.005) reductions in the percentages of areas of intestinal IVOC tissues giving positive staining results for acidic mucins. Conversely, the quantity of neutrally charged mucins present within the goblet cells of the IVOC tissues increased significantly (P < 0.05). In addition, tubulin-α was expressed at high levels following inoculation of jejunal IVOC tissues with L. plantarum. Although L. plantarum JC1 did not reduce the association of S. Typhimurium strain SL1344 to the jejunal IVOC tissues, detection of increased acidic mucin secretion, host cytoskeletal rearrangements, and proteins involved in the porcine immune response demonstrated that this strain of L. plantarum may contribute to protecting the pig from infections by S. Typhimurium or other pathogens.

Prebiotic effect of fruit and vegetable shots containing Jerusalem artichoke inulin: a human intervention study.

The present study aimed to determine the prebiotic effect of fruit and vegetable shots containing inulin derived from Jerusalem artichoke (JA). A three-arm parallel, placebo-controlled, double-blind study was carried out with sixty-six healthy human volunteers (thirty-three men and thirty-three women, age range: 18-50 years). Subjects were randomised into three groups (n 22) assigned to consume either the test shots, pear-carrot-sea buckthorn (PCS) or plum-pear-beetroot (PPB), containing JA inulin (5 g/d) or the placebo. Fluorescent in situ hybridisation was used to monitor populations of total bacteria, bacteroides, bifidobacteria, Clostridium perfringens/histolyticum subgroup, Eubacterium rectale/Clostridium coccoides group, Lactobacillus/Enterococcus spp., Atopobium spp., Faecalibacterium prausnitzii and propionibacteria. Bifidobacteria levels were significantly higher on consumption of both the PCS and PPB shots (10.0 (sd 0.24) and 9.8 (sd 0.22) log10 cells/g faeces, respectively) compared with placebo (9.3 (sd 0.42) log10 cells/g faeces) (P < 0.0001). A small though significant increase in Lactobacillus/Enterococcus group was also observed for both the PCS and PPB shots (8.3 (sd 0.49) and 8.3 (sd 0.36) log10 cells/g faeces, respectively) compared with placebo (8.1 (sd 0.37) log10 cells/g faeces) (P = 0.042). Other bacterial groups and faecal SCFA concentrations remained unaffected. No extremities were seen in the adverse events, medication or bowel habits. A slight significant increase in flatulence was reported in the subjects consuming the PCS and PPB shots compared with placebo, but overall flatulence levels remained mild. A very high level of compliance (>90 %) to the product was observed. The present study confirms the prebiotic efficacy of fruit and vegetable shots containing JA inulin.

In vitro evaluation of the fermentation properties and potential prebiotic activity of Agave fructans.

AIMS: This study was carried out to evaluate in vitro the fermentation properties and the potential prebiotic activity of Agave-fructans extracted from Agave tequilana (Predilife). METHODS AND RESULTS: Five different commercial prebiotics were compared using 24-h pH-controlled anaerobic batch cultures inoculated with human faecal slurries. Measurement of prebiotic efficacy was obtained by comparing bacterial changes, and the production of short-chain fatty acids (SCFA) was also determined. Effects upon major groups of the microbiota were monitored over 24 h incubations by fluorescence in situ hybridization. SCFA were measured by HPLC. Fermentation of the Agave fructans (Predilife) resulted in a large increase in numbers of bifidobacteria and lactobacilli. CONCLUSIONS: Under the in vitro conditions used, this study has shown the differential impact of Predilife on the microbial ecology of the human gut. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study reporting of a potential prebiotic mode of activity for Agave fructans investigated which significantly increased populations of bifidobacteria and lactobacilli compared to cellulose used as a control.

Bioaccessibility of Difenoconazole in Rice Following Industry Standard Processing and Preparation Procedures.

For pesticide registration a post application assessment is made on the safety of any residue remaining in the edible portion of the treated crop. This assessment does not typically consider the bioaccessibility of pesticide residues. The effects of this on potential exposure to incurred difenoconazole residues passing through the human gastrointestinal tract were studied, including the impact of commodity processing. It has previously been demonstrated that solvent extraction methods have the potential to overestimate the bioaccessible fraction, so in vitro simulated gut systems may offer a better approach to determine residue bioaccessibility to refine the risk assessment process. The bioaccessibility of difenoconazole residues associated with processed rice samples was assessed using in vitro intestinal extraction and colonic fermentation methods. The mean bioaccessibility following intestinal digestion was 33.3% with a range from 13% to 70.6%. Quantification of the colonic bioaccessible fraction was not possible due to compound metabolism. Mechanical processing methods generally increased the residue bioaccessibility, while chemical methods resulted in a decrease. Both mechanical and chemical processing methods reduced the total difenoconazole residue level by ca. 50%.

Potential prebiotic activity of oligosaccharides obtained by enzymatic conversion of durum wheat insoluble dietary fibre into soluble dietary fibre.

BACKGROUND AND AIMS: Epidemiological evidence indicates that cereal dietary fibre (DF) may have several cardiovascular health benefits. The underlying mechanisms have not yet been elucidated. Here, the potential nutritional effects of physico-chemical properties modifications of durum wheat dietary fibre (DWF) induced by enzyme treatment have been investigated. METHODS AND RESULTS: The conversion of the highly polymerised insoluble dietary fibre into soluble feruloyl oligosaccharides of DWF was achieved by a tailored enzymatic treatment. The in vitro fermentation and release of ferulic acid by intestinal microbiota from DWF before and after the enzymatic treatment were assessed using a gut model validated to mimic the human colonic microbial environment. Results demonstrated that, compared to DWF, the enzyme-treated DWF (ET-DWF) stimulated the growth of bifidobacteria and lactobacilli. Concurrently, the release of free ferulic acid by ET-DWF was almost three times higher respect to the control. No effect on the formation of short chain fatty acids was observed. CONCLUSIONS: The conversion of insoluble dietary fibre from cereals into soluble dietary fibre generated a gut microbial fermentation that supported bifidobacteria and lactobacilli. The concurrent increase in free ferulic acid from the enzyme-treated DWF might result in a higher plasma ferulic acid concentration which could be one of the reasons for the health benefits reported for dietary fibre in cardiovascular diseases.

The role of microbiota and inflammation in self-judgement and empathy: implications for understanding the brain-gut-microbiome axis in depression.

RATIONALE: The gut-brain axis includes bidirectional communication between intestinal microbiota and the central nervous system. Bifidobacterium and Lactobacillus spp. have been implicated in psychological health, such as depression, through various pathways (e.g. inflammation). Research needs a better understanding of direct and indirect effects through examination of psychological factors that make people susceptible to, or offer protection against, depression. OBJECTIVE: This study investigated the relationships between gut microbiota, inflammation and psychological risk and resilience factors for depression. METHODS: Forty participants (13 m/27 f) recruited from the general population completed self-report questionnaires for depression, self-judgement, over-identification and affective and cognitive empathy. Faecal and blood samples were taken to assay microbiota (Bifidobacterium; Lactobacillus spp.) and pro-inflammatory molecules (C-reactive protein, CRP and interleukin-6, IL-6), respectively. RESULTS: Hierarchical regression analyses (controlling for sex, age and the shared variance of risk and resilience factors) showed that (i) cognitive depression was significantly predicted by negative self-judgement and reduced cognitive empathy; (ii) abundance of Lactobacillus spp. was directly related to positive self-judgement but only indirectly to cognitive depression and lower affective empathy (both through self-judgement); and (iii) CRP was the strongest predictor of reduced cognitive empathy, with suppression effects seen for age (negative) and IL-6 (positive) after controlling for CRP. CONCLUSIONS: Findings suggest that lactobacilli and inflammation may be differentially associated with mood disorder via brain mechanisms underpinning self-judgement and cognitive empathy, respectively. Further trials investigating interventions to increase Lactobacillus spp. in depression would benefit from direct measures of self-judgement and affective empathic distress, whilst those that aim to reduce inflammation should investigate cognitive empathy.

In vitro effects of phosphatidylcholine and transgalactooligosaccharides on the production of 1,2-sn-diacylglycerol by Bifidobacterium longum biovar infantis.

AIMS: To investigate the production of the tumour promoter 1,2-sn-diacylglycerol (DAG) by a human gut isolate of Bifidobacterium longum biovar infantis. METHODS AND RESULTS: Bifidobacterium longum biovar infantis was grown in vitro using anaerobic static batch cultures in the presence of phosphatidylcholine (PC) and trans-galactooligosaccharides (TOS). Production of DAG was found to be dependent upon the presence of PC, while TOS had a reducing effect. Considerable differences in morphology, growth and metabolic end products from the micro-organism were observed under the different culture conditions. CONCLUSIONS: Our results have provided evidence that B. longum biovar infantis can produce DAG in vitro and that a prebiotic exerted a reducing effect upon this production. SIGNIFICANCE AND IMPACT OF THE STUDY: The results presented in this study demonstrate an ability of ostensibly beneficial member of the colonic environment to produce unwanted compounds under certain conditions. Therefore, it may be important that a combination of substrates and other factors are assessed when studying the behaviour of any bacterial group or species, especially when designing the dietary interventions.

Dietary glycated protein modulates the colonic microbiota towards a more detrimental composition in ulcerative colitis patients and non-ulcerative colitis subjects.

AIM: To investigate the effect of native, heated and glycated bovine serum albumin (BSA) on the ulcerative colitis (UC) and non-UC colonic microbiota in vitro. METHODS AND RESULTS: Continuous flow culture (CFC) models of the human colonic microbiota inoculated with faeces from UC and non-UC volunteers were maintained on BSA as growth substrate. Changes in bacterial populations and short-chain fatty acids were determined. UC and non-UC microbiota differed significantly in microbial populations, with elevated numbers of sulfate-reducing bacteria (SRB) and clostridia in the microbiota from UC patients. Compared with native BSA, glycated BSA modulated the gut microbiota of UC patients in vitro towards a more detrimental community structure with significant increases in putatively harmful bacteria (clostridia, bacteroides and SRB; P < 0.009) and decreases in dominant and putatively beneficial bacterial groups (eubacteria and bifidobacteria; P < 0.0004). The levels of beneficial short-chain fatty acids were significantly decreased by heated or glycated BSA, but were increased significantly by native BSA. CONCLUSION: The UC colonic microbiota maintained in CFC was significantly modified by glycated BSA. SIGNIFICANCE AND IMPACT OF THE STUDY: Results suggest that dietary glycated protein may impact upon the composition and activity of the colonic microbiota, an important environmental variable in UC.

Oligosaccharide-mediated inhibition of the adhesion of pathogenic Escherichia coli strains to human gut epithelial cells in vitro.

The aim of the study was to investigate the ability of pectic oligosaccharides (POS) to inhibit adhesion of three strains of verotoxigenic Escherichia coli, three strains of enteropathogenic E. coli, and one nonclinical strain of Desulfovibrio desulfuricans to human intestinal epithelial cell cultures. Lactobacillus acidophilus and Lactobacillus gasseri were included for comparison. Attachment was determined in the human HT29 cell line by viable count of adherent bacteria. POS in buffer at pH 7.2 were antiadhesive at a dose of 2.5 mg ml(-1), reducing adhesion of enteropathogenic E. coil and verotoxigenic E. coli strains to less than 30% of control values. Concentrations resulting in 50% inhibition ranged from 0.15 to 0.46 mg ml(-1). L. acidophilus was not significantly affected, but adhesion of L. gasseri was reduced to 29% of the control value. POS reduced the adhesion of D. desulfuricans to 0.33% of the control value. POS also had a protective effect against E. coli verocytotoxins VT1 and VT2 at concentrations of 0.01 and 1 microg ml(-1), respectively.