S0480 Portable Hydrogen Breath Testing and Microbiome Analysis Identifies Prebiotic-Induced Increases in Colonic Fermentation and Bifidobacterium

Abstract

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.