Current issues in intestinal microbiology最新文献

Acidified feeding formulas have been proposed as a method of controlling gastrointestinal colonization and nosocomial infection in critically ill patients. We examined possible mechanisms by which chronic acid water feeding might protect the host against lethal gut derived sepsis by assessing its effect on both local intestinal epithelial barrier function to bacteria as well as on local and systemic heat shock protein expression. Heat shock protein expression measured by immunoblot demonstrated that HSP25 was increased in the stomach, aorta and kidney of mice chronically fed acid water (8 weeks) compared to tap water fed controls. HSP72 expression was also increased in the aorta of mice drinking acid water. The protein content of cecum and its barrier function were enhanced in mice ingesting acidified water. The direct effect of an acid environment on intestinal epithelial barrier function was tested in cultured human intestinal epithelial cells. An acidified environment protected against bacterial mediated disruption of the intestinal epithelial barrier. Finally, the protective effect of chronic acid water feeding on gut-derived sepsis due to P. aeruginosa was tested in mice. Chronic acid water feeding protected mice from the lethal gut derived sepsis due to P. aeruginosa.

The aim of this study was to develop selectively fermented (prebiotic) carbohydrate molecules which would also result in the generation of butyric acid. Gluco-oligosaccharides produced by Gluconobacter oxydans NCIMB 4943 from various types of maltodextrins were evaluated for their fermentation by mixed cultures of human colonic microflora. The selectivity of growth of desirable bacteria (bifidobacteria, lactobacilli) was studied in stirred pH-controlled (6.8) batch cultures. Bacterial populations were enumerated using fluorescent in situ hybridization (FISH). Gluco-oligosaccharides resulted in significantly (P<0.05) increased numbers of bifidobacteria and lactobacilli within 24 hours. Bacteroides, clostridial and eubacterial populations were slightly decreased at 48 h. There was very little difference in selectivity between the maltodextrin substrates and the products, although maltodextrin displayed a slightly less selective fermentation than the gluco-oligosaccharide products, also stimulating the growth of bacteroides, clostridia and eubacteria. Gluco-oligosaccharides, produced from G19 maltodextrin, resulted in the best prebiotic effect with the highest prebiotic index (PI) of 5.90 at 48 hours. Acetate, propionate and butyrate were all produced from gluco-oligosaccharides, derived from G19 maltodextrin, at 48 hours but no lactate or formate were detected.

Gluco-oligosaccharides produced by Gluconobacter oxydans NCIMB 4943 from maltodextrin as the source, were evaluated for their fermentability by the human colonic microflora. The selectivity of growth of desirable bacteria in the human colon was studied in a three-stage continuous model of the human large intestine. Populations of bacteria, and their fluctuations as a response to the fermentation, were enumerated using fluorescent in situ hybridization (FISH). The gluco-oligosaccharides resulted in increases in numbers of bifidobacteria and the Lactobacillus/Enterococcus group in all 3 vessels of the system, representing the proximal, transverse and distal colonic areas. The prebiotic indices of the gluco-oligosaccharides were 2.29, 4.23 and 2.74 in V1, V2 and V3 respectively.

While prebiotic substances have attracted considerable attention in terms of their stimulatory effect on intestinal calcium absorption, the potential influence of probiotic bacteria on calcium absorption has received little research emphasis. Therefore, the objective of this study was to investigate the effect of well-characterized probiotics (Lactobacillus salivarius (UCC 118) and Bifidobacterium infantis (UCC 35624)) on calcium uptake and transepithelial calcium transport in human intestinal-like, Caco-2, cells in culture. Cells were seeded onto permeable transport membranes and allowed to differentiate, over 16 d, into intestinal-like cell monolayers. Monolayers (n=12-20/ treatment) were then exposed to E. coli UCC 118, UCC 35624 (10(7) cfu/ml) or no bacteria (control) for 6 or 24 h prior to calcium transport studies. Calcium transport was unaffected by exposure of Caco-2 cells to E. coli, UCC 118 or UCC 35624 for 6 or 24 h. Calcium uptake into Caco-2 cell monolayers after 24 h was unaffected by UCC 35624, but was significantly (P<0.05) or tended (P=0.079) to be increased by UCC 118 and E. coli, respectively, relative to the control. In conclusion, the findings of this study which suggest that bacteria can enhance intestinal calcium uptake, if not calcium transport, highlights the need to undertake further studies in this, to date, vastly underinvestigated area.

Terminal-restriction fragment length polymorphism (T-RFLP) was used to evaluate how to store intestinal specimens for bacterial community analysis. Bacterial communities are increasingly often described by means of DNA-based methods and it is common practice to store intestinal or faecal specimens either at -20 degrees C or -80 degrees C. In this study, samples of intestines from five different pigs were stored at -80 degrees C and -20 degrees C, respectively and a thawing and freezing procedure was carried out three times for each intestinal per pig per temperature. The cumulative sum of the T-RFLP peak heights (T-RF intensities) decreased as the temperature decreased. The composition of the bacterial community changed when stored at -80 degrees C compared to the samples stored at -20 degrees C. Thus it is recommended from this study that samples of intestinal content are stored at -20 degrees C before use for bacterial community analysis, instead of the current practice at -80 degrees C.

Escherichia coli O157 and Salmonella spp. are among the leading causes of food-borne illness in the United Sates and bacteria have been isolated from numerous ruminant animal sources. The objective of this study was to assess the incidence of E. coli O157 and Salmonella spp. in white-tailed deer (Odocoileus virginianus) and livestock simultaneously grazing the same rangeland. Escherichia coli O157 was found in 1.25% of cattle, 1.22% of sheep, and 5.00% of water all from samples taken in September; however, no E. coli O157 was found in other sampled months or any species. Salmonella spp. were found in the highest quantities in deer and sheep, 7.69% and 7.32%, respectively. Salmonella spp. were also found in sampled water troughs, goats, and cattle (5.00%, 3.70%, and 1.25%, respectively). Further research examining pathogen distribution is needed to determine if white-tailed deer are a natural reservoir for these bacteria.

On August 29-31, 2004, 84 academic and industry scientists from 16 countries gathered in Copper Mountain, Colorado USA to discuss certain issues at the forefront of the science of probiotics and prebiotics. The format for this invitation only meeting included six featured lectures: engineering human vaginal lactobacilli to express HIV-inhibitory molecules (Peter Lee, Stanford University), programming the gut for health (Thaddeus Stappenbeck, Washington University School of Medicine), immune modulation by intestinal helminthes (Joel Weinstock, University of Iowa Hospitals and Clinics), hygiene as a cause of autoimmune disorders (G. A. Rook, University College London), prebiotics and bone health (Connie Weaver, Purdue University) and prebiotics and colorectal cancer risk (Ian Rowland, Northern Ireland Centre for Food and Health). In addition, all participants were included in one of eight discussion groups on the topics of engineered probiotics, host-commensal bacteria communication, 'omics' technologies, hygiene and immune regulation, biomarkers for healthy people, prebiotic and probiotic applications to companion animals, development of a probiotic dossier, and physiological relevance of prebiotic activity. Brief conclusions from these discussion groups are summarized in this paper.

Protozoan programmed cell death or apoptosis is an important factor in the survival of the parasite and its pathogenicity. The most amazing aspect of protozoan cell death is in its molecular architecture. To date, protozoa lack most of the components of the highly complex cell death machinery studied in multicellular organisms. Hence the unique apoptotic machinery in protozoa can be exploited for the development of therapeutic drugs and diagnostic markers. This review focuses on human intestinal protozoa undergoing cell death and inducing or inhibiting host cell apoptosis. The first part of this review focuses on intestinal protozoa that undergo PCD under various stress conditions. The second part focuses on protozoa that induce or inhibit PCD in their host cell. Although these intestinal parasites differ in their mechanism of infection and intracellular localization, they may activate conserved cell death pathways within themselves and in the host cell. Understanding conserved cell death pathways in the intestinal protozoa and their host-parasite PCD relationship may lead to drug targets which can be used for a broad range of parasitic diseases.

An elaborate feeding regimen of animals, which takes advantage of the Achilles' heels of enteropathogenic bacteria, can possibly enable prophylaxis in the intestinal tract, attenuate actual disease symptoms, accelerate recovery from a bacterial gastroenteritis or ensure food safety. There is a wide spectrum of conceivable weak spots in bacteria. Some pathogenic bacteria cannot use certain compounds, or use them less efficient than beneficial bacteria. By addition of such substances to animal feed, non-pathogenic bacteria can grow better than pathogens and competitively exclude the latter ones. Other compounds even have an inhibitory effect on pathogens. Calcium phosphate for example protects against Salmonella, Zn2+ has a prophylactic effect against Brachyspira, and Fe2+ has an inhibiting effect on the enterotoxin synthesis of Yersinia enterocolitica. Besides, there are antimicrobial substances as plant extracts, essential oils, organic acids and other compounds, which inhibit pathogens more than other bacteria. A simultaneous application of several anti-pathogen agents suggest an enhanced effect. Some countermeasures aim at a distinct group of bacteria, while others are more universal. General strategies to repel different pathogenic bacteria are the supply of health-stimulating milk components, antagonistic bacteria for competitive exclusion, and mucus-related attractants for misguidance of adhering and invasive bacteria. This paper gives an overview of Achilles' heels of enteropathogenic bacteria that can be exploited to develop strategies for keeping control over these pathogens in the gastrointestinal tract of livestock.

Although the intestinal flora in animals plays an important role in health and disease, there is little direct information regarding the role of the human intestinal flora. By inoculating germfree animals with human faeces, the major components of the human flora can be transferred into the ex-germfree animals, i.e. human flora-associated (HFA) animals. HFA animals therefore provide a stable model for studying the ecosystem and metabolism of the human intestinal flora. Results with HFA animals suggest the role of the human intestinal flora is somewhat different from the role of the animal flora in conventional experimental animals. Studies using HFA animals, therefore, will provide much needed information on the precise role of the intestinal flora in relation to humans. HFA animals also can be used as models to investigate the interactions between the human intestinal flora, host factors, dietary manipulations, and therapeutics, such as probiotics, prebiotics, and antibiotics.