The nature of the aerobic gastrointestinal bacteria of cichlid fish Sarotherodon mossambicus (Peters) and Tilapia nilotica (Linnaeus) grown under captivity

Bacteriological examination of the gastrointestinal microflora of 2 freshwater cichlid fish species (Sarotherodon mossambicus and Tilapia nilotica ) was performed, resulting in the bacteria enumeration of total viable counts of 1.06x10⁷/g and 7.75x10⁷/g of gastro-bacteria intestinal tract plus contents (wet weight) respectively, by aerobic incubation at 30+1°C. The majority (78%) of the total gut isolates from both fish species was Gram positive mesophilic which is characteristic of the higher ambient temperature in the tropics. These isolates were fastidious in their nutritional requirements and together with the rest are isogenous to bacteria autochthonous to soil and water. The occurrence of such organisms is attributed to the feeding habits of these fish. The gastrointestinal bacteria isolated in this study are transient residents but not "indigenous" in these cichlid fish.

Intestinal microflora of human infants and current trends for its nutritional modulation

Diet, among other environmental and genetic factors, is currently recognised to have an important role in health and disease. There is increasing evidence that the human colonic microbiota can contribute positively towards host nutrition and health. As such, dietary modulation has been proposed as important for improved gut health, especially during the highly sensitive stage of infancy. Differences in gut microflora composition and incidence of infection occur between breast- and formula-fed infants. Human milk components that cannot be duplicated in infant formulae could possibly account for these differences. However, various functional food ingredients such as oligosaccharides, prebiotics, proteins and probiotics could effect a beneficial modification in the composition and activities of gut microflora of infants. The aim of the present review is to describe existing knowledge on the composition and metabolic activities of the gastrointestinal microflora of human infants and discuss various possibilities and opportunities for its nutritional modulation.

Relationship between dietary-induced changes in intestinal commensal microflora and duodenojejunal myoelectric activity monitored by radiotelemetry in the rat in vivo

Interdigestive intestinal motility, and especially phase III of the migrating myoelectric/motor complex (MMC), is responsible for intestinal clearance and plays an important role in prevention of bacterial overgrowth and translocation in the gut. Yet previous results from gnotobiotic rats have shown that intestinal microflora can themselves affect the characteristics of the myoelectric activity of the gut during the interdigestive state. Given that the composition of the intestinal microflora can be altered by dietary manipulations, we investigated the effect of supplementation of the diet with synbiotics on intestinal microflora structure and the duodenojejunal myoelectric activity in the rat. To reduce animal distress caused by restraint and handling, which can itself affect GI motility, we applied radiotelemetry for duodenojejunal EMG recordings in conscious, freely moving rats. Thirty 16-month-old Spraque-Dawley rats were used. The diet for 15 rats (E group) was supplemented with chicory inulin, Lactobacillus rhamnosus and Bifidobacterium lactis. The remaining 15 rats were fed control diet without supplements (C group). Three rats from each group were implanted with three bipolar electrodes positioned at 2, 14 and 28 cm distal to the pylorus. After recovery, two 6 h recordings of duodenojejunal EMG were carried out on each operated rat. Subsequently, group C rats received feed supplements and group E rats received only control diet for 1 week, and an additional two 6 h recordings were carried out on each of these rats. Non-operated C and E rats were killed and samples of GI tract were collected for microbiological analyses. Supplementation of the diet with the pro- and prebiotics mixture increased the number of bifidobacteria, whereas it decreased the number of enterobacteria in jejunum, ileum, caecum and colon. In both caecum and colon, the dietary supplementation increased the number of total anaerobes and lactobacilli. Treatment with synbiotics increased occurrence of phase III of the MMC at all three levels of the small intestine. The propagation velocity of phase III in the whole recording segment was also increased from 3.7 +/- 0.2 to 4.4 +/- 0.2 cm min(-1) by dietary treatment. Treatment with synbiotics increased the frequency of response potentials of the propagated phase III of the MMC at both levels of the jejunum, but not in the duodenum. In both parts of the jejunum, the supplementation of the diet significantly decreased the duration of phase II of the MMC, while it did not change the duration of phase I and phase III. Using the telemetry technique it was demonstrated that changes in the gastrointestinal microflora exhibited an intestinal motility response and, more importantly, that such changes can be initiated by the addition of synbiotics to the diet.

A two-stage continuous culture system to study the effect of supplemental alpha-lactalbumin and glycomacropeptide on mixed cultures of human gut bacteria challenged with enteropathogenic Escherichia coli and Salmonella serotype Typhimurium

Aims: Certain milk factors may promote the growth of a gastrointestinal microflora predominated by bifidobacteria and may aid in overcoming enteric infections. This may explain why breast-fed infants experience fewer intestinal infections than their formula-fed counterparts. The effect of formula supplementation with two such factors was investigated in this study. Methods and Results: Infant faecal specimens were used to ferment formulae supplemented with glycomacropeptide (GMP) and alpha-lactalbumin (alpha-la) in a two-stage compound continuous culture model. At steady state, all fermenter vessels were inoculated with 5 ml of 0.1 M phosphate-buffered saline (pH 7.2) containing 10(8) CFU ml(-1) of either enteropathogenic Escherichia coli 2348/69 (O127:H6) or Salmonella serotype Typhimurium (DSMZ 5569). Bacteriology was determined by independent fluorescence in situ hybridization. Vessels that contained breast milk (BM), as well as alpha-la and GMP supplemented formula had stable total counts of bifidobacteria while lactobacilli increased significantly only in vessels with breast milk. Bacteroides, clostridia and E. coli decreased significantly in all three groups prior to pathogen addition. Escherichia coli counts decreased in vessels containing BM and alpha-la while Salmonella decreased significantly in all vessels containing BM, alpha-la and GMP. Acetate was the predominant acid. Significance and Impact of the Study: Supplementation of infant formulae with appropriate milk proteins may be useful in mimicking the beneficial bacteriological effects of breast milk.

Use of batch culture and a two-stage continuous culture system to study the effect of supplemental a-lactalbumin and glycomacropeptide on mixed populations of human gut bacteria

Certain milk factors can promote the growth of a host-friendly gastrointestinal microflora. This may explain why breast-fed infants experience fewer intestinal infections than their formula-fed counterparts. The effect of formula supplementation with two such factors was investigated in this study. Infant faecal specimens were used to ferment formulas supplemented with glycomacropeptide and α-lactalbumin in a two-stage compound continuous culture model. Bacteriology was determined by fluorescence in situ hybridisation. Vessels that contained breast milk as well as α-lactalbumin and glycomacropeptide had stable counts of bifidobacteria while lactobacilli increased significantly only in vessels with breast milk. Bacteroides, clostridia and Escherichia coli decreased significantly in all runs. Acetate was the principal acid found along with high amounts of propionate and lactate. Supplementation of infant formulas with appropriate milk proteins may be useful in simulating the beneficial bacteriological effects of breast milk.

Molecular characterization of the microbial species that colonize human ileal and colonic mucosa by using 16S rDNA sequence analysis

Aim: The aim of this study was to characterize the bacterial community adhering to the mucosa of the terminal ileum, and proximal and distal colon of the human digestive tract. Methods and Results: Pinch samples of the terminal ileum, proximal and distal colon were taken from a healthy 35-year-old, and a 68-year-old subject with mild diverticulosis. The 16S rDNA genes were amplified using a low number of PCR cycles, cloned, and sequenced. In total, 361 sequences were obtained comprising 70 operational taxonomic units (OTU), with a calculated coverage of 82.6%. Twenty-three per cent of OTU were common to the terminal ileum, proximal colon and distal colon, but 14% OTU were only found in the terminal ileum, and 43% were only associated with the proximal or distal colon. The most frequently represented clones were from the Clostridium group XIVa (24.7%), and the Bacteroidetes (Cytophaga-Flavobacteria-Bacteroides ) cluster (27.7%). Conclusion: Comparison of 16S rDNA clone libraries of the hindgut across mammalian species confirms that the distribution of phylogenetic groups is similar irrespective of the host species. Lesser site-related differences within groups or clusters of organisms, are probable. Significance and Impact: This study provides further evidence of the distribution of the bacteria on the mucosal surfaces of the human hindgut. Data contribute to the benchmarking of the microbial composition of the human digestive tract.

Survivability of a probiotic Lactobacillus casei in the gastrointestinal tract of healthy human volunteers and its impact on the faecal microflora

Aim: The aim of this study was to measure the gastrointestinal survival of Lactobacillus casei and its impact on the gut microflora in healthy human volunteers. Methods and Results: Twenty healthy volunteers took part in a double-blind placebo-controlled probiotic feeding study (10 fed probiotic, 10 fed placebo). The probiotic was delivered in two 65 ml aliquots of fermented milk drink (FMD) daily for 21 days at a dose of 8.6 +/- 0.1 Log(10)Lact. casei CFU ml(-1) FMD. Faecal samples were collected before, during and after FMD or placebo consumption, and important groups of faecal bacteria enumerated by fluorescent in situ hybridization (FISH) using oligonucleotide probes targeting the 16S rRNA. The fed Lact. casei was enumerated using selective nutrient agar and colony identity confirmed by pulsed field gel electrophoresis. Seven days after ingestion of FMD, the Lact. casei was recovered from faecal samples taken from the active treatment group at 7.1 +/- 0.4 Log(10) CFU g(-1) faeces (mean +/- SD, n = 9) and numbers were maintained at this level until day 21. Lact. casei persisted in six volunteers until day 28 at 5.0 +/- 0.9 Log(10) CFU g(-1) faeces (mean +/- SD, n = 6). Numbers of faecal lactobacilli increased significantly upon FMD ingestion. In addition, the numbers of bifidobacteria were higher on days 7 and 21 than on days 0 and 28 in both FMD fed and placebo fed groups. Consumption of Lact. casei had little discernible effect on other bacterial groups enumerated. Conclusions: Daily consumption of FMD enabled a probiotic Lact. casei strain to be maintained in the gastrointestinal tract of volunteers at a stable relatively high population level during the probiotic feeding period. Significance and Impact of the Study: The study has confirmed that this probiotic version of Lact. casei survives well within the human gastrointestinal tract.

The fate of olive oil polyphenols in the gastrointestinal tract: implications of gastric and colonic microflora-dependent biotransformation

We have conducted a detailed investigation into the absorption, metabolism and microflora-dependent transformation of hydroxytyrosol ( HT), tyrosol (TYR) and their conjugated forms, such as oleuropein (OL). Conjugated forms underwent rapid hydrolysis under gastric conditions, resulting in significant increases in the amount of free HT and TYR entering the small intestine. Both HT and TYR transferred across human Caco-2 cell monolayers and rat segments of jejunum and ileum and were subject to classic phase I/II biotransformation. The major metabolites identified were an O-methylated derivative of HT, glucuronides of HT and TYR and a novel glutathionylated conjugate of HT. In contrast, there was no absorption of OL in either model. However, OL was rapidly degraded by the colonic microflora resulting in the formation of HT. Our study provides additional information regarding the breakdown of complex olive oil polyphenols in the GI tract, in particular the stomach and the large intestine.

Fermentation of heated gluten systems by gut microflora

The Maillard reaction causes changes to protein structure and occurs in foods mainly during thermal treatment. Melanoidins, the final products of the Maillard reaction, may enter the gastrointestinal tract, which is populated by different species of bacteria. In this study, melanoidins were prepared from gluten and glucose. Their effect on the growth of faecal bacteria was determined in culture with genotype and phenotype probes to identify the different species involved. Analysis of peptic and tryptic digests showed that low molecular mass products are formed from the degradation of melanoidins. Results showed a change in the growth of bacteria. This in vitro study demonstrated that melanoidins, prepared from gluten and glucose, affect the growth of the gut microflora.

Modulation of the fecal microflora profile and immune function by a novel trans-galactooligosaccharide mixture (B-GOS) in healthy elderly volunteers

Background: Aging is associated with reduced numbers of beneficial colonic bifidobacteria and impaired immunity. Galactooligosaccharides (GOSs) stimulate the growth of bifidobacteria in younger adults, but little is known about their effects in the elderly and their immunomodulatory capacity. Objective: We assessed the effect of a prebiotic GOS mixture (B-GOS) on immune function and fecal microflora composition in healthy elderly subjects. Design: In a double-blind, placebo-controlled, crossover study, 44 elderly subjects were randomly assigned to receive either a placebo or the B-GOS treatment (5.5 g/d). Subjects consumed the treatments for 10 wk, and then went through a 4-wk washout period, before switching to the other treatment for the final 10 wk. Blood and fecal samples were collected at the beginning, middle (5 wk), and end of the test period. Predominant bacterial groups were quantified, and phagocytosis, natural killer (NK) cell activity, cytokine production, plasma cholesterol, and HDL cholesterol were measured. Results: B-GOS significantly increased the numbers of beneficial bacteria, especially bifidobacteria, at the expense of less beneficial groups compared with the baseline and placebo. Significant increases in phagocytosis, NK cell activity, and the production of antiinflammatory cytokine interleukin-10 (IL-10) and significant reduction in the production of proinflammatory cytokines (IL-6, IL-1 beta , and tumor necrosis factor-alpha) were also observed. B-GOS exerted no effects on total cholesterol or HDL-cholesterol production, however. Conclusions: B-GOS administration to healthy elderly persons resulted in positive effects on both the microflora composition and the immune response. Therefore, B-GOS may be a useful dietary candidate for the enhancement of gastrointestinal health and immune function in elderly persons. Am J Clin Nutr 2008; 88: 1438-46.

Modulation of the human gut microflora towards improved health using prebiotics: assessment of efficacy

There is increasing awareness that the human gut microflora plays a critical role in maintaining host health, both within the gastrointestinal tract and, through the absorption of metabolites, systemically. An 'optimal' gut microflora establishes an efficient barrier to the invasion and colonisation of the gut by pathogenic bacteria, produces a range of metabolic substrates which in turn are utilized by the host (e.g. vitamins and short chain fatty acids) and stimulates the immune system in a non-inflammatory manner. Although little is known about the individual species of bacteria responsible for these beneficial activities, it is generally accepted that the bifidobacteria and lactobacilli constitute important components of the beneficial gut microflora. A number of diet-based microflora management tools have been developed and refined over recent decades including probiotic, prebiotic and synbiotic approaches. Each aims to stimulate numbers and/or activities of the bifidobacteria and lactobacilli within the gut microflora. The aim of this article is to examine how prebiotics are being applied to the improvement of human health and to review the scientific evidence supporting their use.

Differences between the gut microflora of children with autistic spectrum disorders and that of healthy children

Children with autistic spectrum disorders (ASDs) tend to suffer from severe gastrointestinal problems. Such symptoms may be due to a disruption of the indigenous gut flora promoting the overgrowth of potentially pathogenic micro-organisms. The faecal flora of patients with ASDs was studied and compared with those of two control groups (healthy siblings and unrelated healthy children). Faecal bacterial populations were assessed through the use of a culture-independent technique, fluorescence in situ hybridization, using oligonucleotide probes targeting predominant components of the gut flora. The faecal flora of ASD patients contained a higher incidence of the Clostridium histolyticum group (Clostridium clusters I and 11) of bacteria than that of healthy children. However, the non-autistic sibling group had an intermediate level of the C. histolyticum group, which was not significantly different from either of the other subject groups. Members of the C. histolyticum group are recognized toxin-producers and may contribute towards gut dysfunction, with their metabolic products also exerting systemic effects. Strategies to reduce clostridial population levels harboured by ASD patients or to improve their gut microflora profile through dietary modulation may help to alleviate gut disorders common in such patients.