Molecular Monitoring of the Fecal Microbiota of Healthy Human Subjects during Administration of Lactulose and Saccharomyces boulardii

Abstract

Diet is a major factor in maintaining a healthy human gastrointestinal tract, and this has triggered the development of functional foods containing a probiotic and/or prebiotic component intended to improve the host's health via modulation of the intestinal microbiota. In this study, a long-term placebo-controlled crossover feeding study in which each subject received several treatments was performed to monitor the effect of a prebiotic substrate (i.e., lactulose), a probiotic organism (i.e., Saccharomyces boulardii), and their synbiotic combination on the fecal microbiota of three groups of 10 healthy human subjects differing in prebiotic dose and/or intake of placebo versus synbiotic. For this purpose, denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene amplicons was used to detect possible changes in the overall bacterial composition using the universal V 3 primer and to detect possible changes at the subpopulation level using group-specific primers targeting the Bacteroides fragilis subgroup, the genus Bifidobacterium, the Clostridium lituseburense group (cluster XI), and the Clostridium coccoides-Eubacterium rectale group (cluster XIVa). Although these populations remained fairly stable based on DGGE profiling, one pronounced change was observed in the universal fingerprint profiles after lactulose ingestion. Band position analysis and band sequencing revealed that a band appearing or intensifying following lactulose administration could be assigned to the species Bifidobacterium adolescentis. Subsequent analysis with real-time PCR (RT-PCR) indicated a statistically significant increase (P < 0.05) in total bifidobacteria in one of the three subject groups after lactulose administration, whereas a similar but nonsignificant trend was observed in the other two groups. Combined RT-PCR results from two subject groups indicated a borderline significant increase (P ‫؍‬ 0.074) of B. adolescentis following lactulose intake. The probiotic yeast S. boulardii did not display any detectable universal changes in the DGGE profiles, nor did it influence the bifidobacterial levels. This study highlighted the capacity of an integrated approach consisting of DGGE analysis and RT-PCR to monitor and quantify pronounced changes in the fecal microbiota of healthy subjects upon functional food administration.

Reproducible Community Dynamics of the Gastrointestinal Microbiota following Antibiotic Perturbation

“…A number of studies have indicated that an individual's gut microbiota can have a relatively stable community composition over a period of months to years (36,49,57,62). These observations have led to the conclusion that the community of microbes in the gut is relatively resistant to perturbation by various ecological stressors.…”

Dynamics of Vaginal Bacterial Communities in Women Developing Bacterial Vaginosis, Candidiasis, or No Infection, Analyzed by PCR-Denaturing Gradient Gel Electrophoresis and Real-Time PCR

“…Two molecular techniques, PCR-DGGE and real-time PCR, were combined to achieve a detailed picture of vaginal ecology under normal and abnormal conditions. This integrated approach has been recently proposed for monitoring the effect of prebiotics, probiotics, and symbiotics on the fecal microbiota of healthy humans (37). Consistent with data from previous studies (4, 10, 12, 24, 41), our DGGE data showed that the vaginal bacterial floras in healthy women were stable over time and dominated by a single species or group of closely related species of Lactobacillus (L. iners, L. acidophilus, L. gasseri, and L. vaginalis).…”

The role of microbiota in hepatic encephalopathy

“…8 Lactulose therapy does not significantly change microbial composition in healthy individuals using culture-independent techniques. 28 Our group evaluated change in microbiota after overt HE therapy was initiated and found that the relative reduction in autochthonous taxa continued despite lactulose therapy. 17 However a systems biology analysis of systematic lactulose withdrawal showed that selected patients have overt HE recurrence once lactulose is withdrawn.…”