Alimentary Health (Ireland)

Introduction The low-FODMAP diet (LFD) is now frequently used in the management of Irritable Bowel Syndrome (IBS). However, the process can be lengthy, has no standardised protocol and relies exclusively on self-reported symptoms, which are subjective and can be unreliable, in particular when they are reported retrospectively. Methods A total of 2423 carbohydrate challenges (695 lactose 25 g, 531 fructose 25 g, 460 sorbitol 10 g & 737 inulin 10 g) were performed by 1349 participants using a portable app-connected breath analysis device from April 2018 until February 2020. The substrate was administered in a fasting state to minimise the likelihood of symptom generation. Upon ingestion of the substrate, breath tests were performed every 15 minutes for 3 hours. The criterion for a positive challenge was a rise in breath hydrogen of 20 ppm or greater from the lowest preceding breath hydrogen measurement. Results It was found that 21% of lactose, 24% of fructose, 55% of sorbitol, and 34% of inulin challenges reached the positive test criterion. The mean time taken to reach this criterion was respectively 1.7 h, 1.0 h, 1.8 h and 2.0 h illustrating some of the temporal dynamics of carbohydrate malabsorption and potential metabolism by the gut microflora (figure 1). The area-under-the-curve (AUC) was 88.6 ppm.h, 87.5 ppm.h, 82.4 ppm.h and 68.8 ppm.h for lactose, fructose, sorbitol and inulin respectively. Conclusions Less than a quarter of lactose or fructose challenges were positive. Despite sorbitol being only passively absorbed (Beaugerie et al, Gastroenterology. 99 (1990): 717–723), 45% of participants yielded a negative challenge. Similarly, for inulin, which is entirely non-absorbable, 66% of participants did not reach the positive test criterion. It is likely that some participants would have eventually reached the criterion for inulin. It is also likely that only some participants are host to the species of colonic bacteria with the capability to cleave inulin’s β(2,1) bonds. It was seen that the chain length greatly affects mean time to reach the positive criterion, despite the AUC being similar for each FODMAP, except inulin. This offers evidence that significant amounts of hydrogen may have continued to be produced in the case of inulin had the challenge duration been extended. Accumulation of the gases produced during the fermentation of FODMAPs is likely one of the leading factors associated with symptom generation in IBS. The observed differences in timing and quantity of breath hydrogen illustrates the complexity of human and bacterial metabolism of the FODMAP substrates. Measuring breath hydrogen subsequent to the ingestion of a fixed FODMAP dose, provides a quantifiable indicator of the volume of colonic gas that would be produced under dietary conditions.

INTRODUCTION: Changes in gut microbiome composition and the attendant health benefits associated with prebiotic intake, vary from person-to-person, implying the need for personalisation. As the primary metabolite of colonic fermentation that can be detected on exhaled breath, hydrogen could be used to indicate when a prebiotic is being metabolized by the host microbiota. METHODS: Volunteers (n = 20) were studied in a double-blind, crossover design (1-week baseline, 2-weeks 1st prebiotic, 2-week wash-out, 2-weeks 2nd prebiotic, 1-week washout) using two different prebiotic fibres, a galacto-oligosaccharide (GOS) and a wheat dextrin (WD). Breath hydrogen scores were recorded using a portable breath analyser, while 6 faecal samples per individual were acquired during the study (2 baseline samples and 4 intervention samples) (Figure 1). Bacterial DNA was extracted and submitted to 16S rRNA sequencing on an iSeq platform (Carbiotix) to characterise the gut microbiota. RESULTS: Five faecal samples were excluded due to low quality DNA. A mean number of 388 breath hydrogen levels were recorded per individual (SD 59). A high degree of interpersonal variation was apparent in both breath hydrogen and microbiome composition. We noted a consistent trend for increased abundance of the genus Bifidobacterium on administration of GOS (group 1, 1% (range 0–2.1) - 3.6% (0.4–14.2), P = 0.004; group 2, 2.4% (0.03–11.6) - 10.2% (0.04–22), P = 0.04) and in one of two groups following WD (group 1, 0.09% (0–10) - 1.1% (0–19), P = 0.04). On an individual level, we saw greater changes in breath hydrogen on administration of GOS, which was less apparent if WD was taken first in sequence. We used repeated-measures-correlation to correlate the relative abundance of bacterial genera with weekly breath hydrogen. Following correction for multiple comparisons, only Bifidobacterium was significantly positively correlated with weekly breath hydrogen (r = 0.35, adjusted P-value = 0.016) (Figure 2). CONCLUSION: These results reflect the known Bifidogenic effects of these prebiotics. Interestingly, Bifidobacterium are unable to produce hydrogen, as they do not possess hydrogenases. However, a possible mechanism is that the fermentation of these prebiotics resulted in an initial increase in hydrogen and other important products, and via cross-feeding, the growth of Bifidobacterium was supported, to varying degrees in all individuals. Future studies are needed to understand the processes at play.Figure 1.: Overview of study. A baseline was established for each user (week one). A prebiotic fibre was taken for a two week period (week two and three), followed by a two week wash-out period (week four and five), before switching to the other prebiotic intervention (week six and seven). No prebiotic was taken during week eight.Figure 2.: Breath hydrogen simple moving average (SMA) and Bifidobacterium abundance levels for one of the study participants for the duration of the study period.

Probiotics are ‘live microorganisms which, when administrated in adequate amounts, confer a health benefit on the host’ (FAO/WHO, 2001). This requirement, i.e. that the probiotic bacteria must be in viable form at the time of consumption, poses a number of technical challenges from food processing perspectives. Environmental stresses encountered during food processing include acid exposure during food fermentations, extremes in temperatures encountered during drying processes, in addition to oxidative, osmotic, and food matrix stresses. Furthermore, the ingested bacteria must remain viable during gastric transit, to reach the site of action in viable form to exert the probiotic effects. This imposes further stresses, as the gastrointestinal tract is naturally designed to impede the passage of microorganisms with low pH encountered in the stomach and the detergent-like properties of bile encountered in the duodenum. A number of approaches have been investigated in order to minimise the damage caused by exposure to such stresses experienced by probiotics during food processing and gastric transit. Approaches for protection of probiotic viability during food processing and shelf life include manipulation of bacterial cell physiology, application of prelethal stress to the cultures during cell preparation, selection of appropriate drying conditions, and optimisation of reconstitution conditions after drying. Furthermore, probiotic viability losses can be minimised by selection of appropriate food carriers for their delivery to the intestine. In this respect, the composition and physical nature of the food matrix can have profound effects on the stability of live probiotics during gastric transit. Encapsulation of probiotics is another approach to positively affect viability of probiotics in some matrices. Furthermore, it is important to understand the mechanisms underlying bacterial survival in hostile environments in order to develop efficacious functional foods delivering the benefits associated with the probiotics within.

BackgroundRespiratory syncytial virus (RSV) causes respiratory tract infections in infants and immunocompromised individuals and has been associated with the development of asthma.ObjectiveTo evaluate the effect of feeding Bifidobacterium longum AH1206, Bifidobacterium breve AH1205, and Lactobacillus salivarius AH102 to RSV infected mice.MethodsBALB/c mice (N=10/group) were fed 109 cfu/day B. longum AH1206, B. breve AH1205, or L. salivarius AH102 for 21 days. On day 14, mice were nasally challenged with RSV. Following infection, mice were weighed and clinically scored daily. On day 21, lungs were harvested for RSV quantification and gene expression analysis of several immune biomarkers. Infected and non‐infected, placebo fed groups served as positive (RSV+) and negative (RSV‐) controls, respectively. Mann‐Whitney t‐test was used to determine statistical differences, p<0.05.ResultsAll RSV infected mice had increases in clinical scores and lost weight post‐infection with no differences among groups. There were no differences in RSV titres or cytokine gene expression among treatments. Compared to the RSV+ control, the AH102 group showed a significantly lower increase in Foxp3 expression (p<0.05). AH1206 showed significant increases in CD86, CD127 and CD11c expression compared to the RSV‐ and RSV+ controls (all p<0.01), AH 1206 also showed a significant increase in CD3 expression compared to RSV‐ (p<0.001).ConclusionStrain‐specific differences were observed in a number of immune cell markers that could play an important role in enhancing clearance and immunity to RSV infection. The clinical relevance of these findings should be the subject of further studies.

Caseicins A and B are low-molecular-weight antimicrobial peptides which are released by proteolytic digestion of sodium caseinate. Caseicin A (IKHQGLPQE) is a nine-amino-acid cationic peptide, and caseicin B (VLNENLLR) is a neutral eight-amino-acid peptide; both have previously been shown to exhibit antibacterial activity against a number of pathogens, including Cronobacter sakazakii. Previously, four variants of each caseicin which differed subtly from their natural counterparts were generated by peptide synthesis. Antimicrobial activity assays revealed that the importance of a number of the residues within the peptides was dependent on the strain being targeted. In this study, this engineering-based approach was expanded through the creation of a larger collection of 26 peptides which are altered in a variety of ways. The investigation highlights the generally greater tolerance of caseicin B to change, the fact that changes have a more detrimental impact on anti-Gram-negative activity, and the surprising number of variants which exhibit enhanced activity against Staphylococcus aureus.