Competitive inhibition of adherence of enterotoxigenic Escherichia coli, enteropathogenic Escherichia coli and Clostridium difficile to intestinal epithelial cell line Lovo by purified adhesin of Bifidobacterium adolescentis 1027

A prebiotic-enhanced lipid-based nutrient supplement (LNSp) increases Bifidobacterium relative abundance and enhances short-chain fatty acid production in simulated colonic microbiota from undernourished infants

Undernutrition remains a public health problem in the developing world with an attributable under-five death proportion of 45%. Lower gut microbiota diversity and poor metabolic output are associated with undernutrition and new therapeutic paths may come from steering gut microbiota composition and functionality. Using a dynamic gut model, the Simulator of Human Intestinal Microbial Ecosystem (SHIME®), we investigated the effect of a lipid-based nutrient supplement enriched with prebiotics (LNSp), compared to LNS alone and control treatment, on the composition and metabolic functionality of fecal microbiota from three infants suffering from undernutrition. LNS elicited a significant increase in acetate and branched-chain fatty acid production, and a higher relative abundance of the genera Prevotella, Megasphaera, Acinetobacter, Acidaminococcus and Pseudomonas. In contrast, LNSp treatment resulted in a significant 9-fold increase in Bifidobacterium relative abundance and a decrease in that of potential pathogens and detrimental bacteria such as Enterobacteriaceae spp. and Bilophila sp. Moreover, the LNSp treatment resulted in a significantly higher production of acetate, butyrate and propionate, as compared to control and LNS. Our results suggest that provision of prebiotic-enhanced LNS to undernourished children could be a possible strategy to steer the microbiota toward a more beneficial composition and metabolic activity. Further in vivo investigations are needed to assess these effects and their repercussion on nutritional status.

Prophylactic Bifidobacterium adolescentis ATTCC 15703 supplementation reduces partially allergic airway disease in Balb/c but not in C57BL/6 mice

Allergic asthma is a chronic disease mainly characterised by eosinophil inflammation and airway remodelling. Many studies have shown that the gut microbiota of allergic individuals differs from that of non-allergic individuals. Although high levels of bifidobacteria have been associated with healthy persons, Bifidobacterium adolescentis ATCC 15703, a gut bacteria, has been associated with allergic individuals in some clinical studies. The relationship between B. adolescentis ATCC 15703 and asthma or allergies has not been well elucidated, and its effect may be dependent on the host's genetic profile or disease state. To elucidate this question, we evaluated the role of preventive B. adolescentis ATCC 15703 treatment on experimental allergic airway inflammation in two genetically different mouse strains, Balb/c and C57BL/6 (B6). Balb/c mice display a greater predisposition to develop allergic responses than B6 mice. Oral preventive treatment with B. adolescentis ATCC 15703 modulated experimental allergic airway inflammation, specifically in Balb/c mice, which showed decreased levels of eosinophils in the airway. B6 mice did not exhibit any significant alterations in eosinophils but showed an increased influx of total leukocytes and neutrophils into the airway. The mechanism underlying the beneficial effects of these bacteria in experimental allergic mice may involve products of bacteria metabolism, as dead bacteria did not mimic the ability of live B. adolescentis ATCC 15703 to attenuate the influx of eosinophils into the airway. To conclude, preventive oral B. adolescentis ATCC 15703 treatment can attenuate the major characteristic of allergic asthma, eosinophil airway influx, in Balb/c but not B6 mice. These results suggest that oral treatment with this specific live bacterial strain may have therapeutic potential for the treatment of allergic airway disease, although its effect is mouse-strain-dependent.

Foodborne enterotoxigenic Escherichia coli: from gut pathogenesis to new preventive strategies involving probiotics

Enterotoxigenic Escherichia coli (ETEC) are a major cause of traveler's diarrhea and infant mortality in developing countries. Given the rise of antibiotic resistance worldwide, there is an urgent need for the development of new preventive strategies. Among them, a promising approach is the use of probiotics. Although many studies, mostly performed under piglet digestive conditions, have shown the beneficial effects of probiotics on ETEC by interfering with their survival, virulence or adhesion to mucosa, underlying mechanisms remain unclear. This review describes ETEC pathogenesis, its modulation by human gastrointestinal cues as well as novel preventive strategies with a particular emphasis on probiotics. The potential of in vitro models simulating human digestion in elucidating probiotic mode of action will be discussed.

The Comparative Pathology of Clostridium difficile-associated Disease

Clostridium difficile is a confirmed pathogen in a wide variety of mammals, but the incidence of disease varies greatly in relation to host species, age, environmental density of spores, administration of antibiotics, and possibly, other factors. Lesions vary as well, in severity and distribution within individuals, and in some instances, age groups, of a given species. The cecum and colon are principally affected in most species, but foals and rabbits develop severe jejunal lesions. Explanations for variable susceptibility of species, and age groups within a species, are largely speculative. Differences in colonization rates and toxin-receptor densities have been proposed. Clostridium difficile-associated disease is most commonly diagnosed in Syrian hamsters, horses, and neonatal pigs, but it is reported sporadically in many other species. The essential virulence factors of C. difficile are large exotoxins, toxin A (TcdA) and toxin B (TcdB). Receptor-mediated endocytosis of the toxins is followed by endosomal acidification, a necessary step for conversion of the toxin to its active form in the cytosol. Cell-surface receptors have been characterized for TcdA, but remain to be identified for TcdB. Both TcdA and TcdB disrupt the actin cytoskeleton by disrupting Rho-subtype, intracellular signaling molecules. Disruption of the actin cytoskeleton is catastrophic for cellular function, but inflammation and neurogenic stimuli are also involved in the pathogenesis of the disease.

Anti-viral Effect of Bifidobacterium adolescentis against Noroviruses

This study aims to investigate the effect of Bifidobacterium adolescentis against noroviruses (NoVs). Murine norovirus-1 (MNV-1) used as a surrogate was detected by plaque assay and RT-qPCR. Human NoV virus like particles (VLPs) were detected by cell-binding assay. It was shown that the presence of B. adolescentis could inhibit the multiplication of MNV-1 on RAW 264.7 cells within 48 h of co-incubation period at 37°C. This inhibition did not occur at the viral binding stage, as no difference was observed in MNV-1 genomic copies collected from washed RAW 264.7 cells without and with B. adolescentis after co-incubation for 1 h at room temperature. Meanwhile, the presence of B. adolescentis decreased the binding of human NoV GI.1 VLPs to both Caco-2 cells and HT-29 cells, while no reduction was induced for the binding of human NoV GII.4 VLPs to Caco-2 cells.

Role of F1C fimbriae, flagella, and secreted bacterial components in the inhibitory effect of probiotic Escherichia coli Nissle 1917 on atypical enteropathogenic E. coli infection

Enteropathogenic Escherichia coli (EPEC) is recognized as an important intestinal pathogen that frequently causes acute and persistent diarrhea in humans and animals. The use of probiotic bacteria to prevent diarrhea is gaining increasing interest. The probiotic E. coli strain Nissle 1917 (EcN) is known to be effective in the treatment of several gastrointestinal disorders. While both in vitro and in vivo studies have described strong inhibitory effects of EcN on enteropathogenic bacteria, including pathogenic E. coli, the underlying molecular mechanisms remain largely unknown. In this study, we examined the inhibitory effect of EcN on infections of porcine intestinal epithelial cells with atypical enteropathogenic E. coli (aEPEC) with respect to single infection steps, including adhesion, microcolony formation, and the attaching and effacing phenotype. We show that EcN drastically reduced the infection efficiencies of aEPEC by inhibiting bacterial adhesion and growth of microcolonies, but not the attaching and effacing of adherent bacteria. The inhibitory effect correlated with EcN adhesion capacities and was predominantly mediated by F1C fimbriae, but also by H1 flagella, which served as bridges between EcN cells. Furthermore, EcN seemed to interfere with the initial adhesion of aEPEC to host cells by secretion of inhibitory components. These components do not appear to be specific to EcN, but we propose that the strong adhesion capacities enable EcN to secrete sufficient local concentrations of the inhibitory factors. The results of this study are consistent with a mode of action whereby EcN inhibits secretion of virulence-associated proteins of EPEC, but not their expression.

Inhibition of enteropathogenic Escherichia coli adhesion on host epithelial cells by Holarrhena antidysenterica (L.) WALL

Bacterial adhesion is the first step in the sequence of events leading to infection. Previous data are available on the effect of Holarrhena antidysenterica on antidiarrhoeal and antibacterial action, but there is little information on the mechanism of action of the various aspects of EPEC-induced diarrhoea, namely adherence and translocation of the effector molecule to intestinal epithelial cells. The aim of the present study was to investigate the effects of alkaloids of Holarrhena antidysenterica (AHA) on interference in the mechanism of enteropathogenic Escherichia coli (EPEC) adhesion on host epithelial cells (INT 407 and HEp2). To determine the impact of AHA on epithelial cells, cytotoxicity (LDH), adherence, apoptotic and ultrastructural studies were performed. To analyse the effect of AHA on EPEC secreted proteins, especially EspD, INT 407 monolayers were infected with EPEC and AHA-treated EPEC, followed by immunoblotting, probed with anti EspD antisera. The maximum percentage of LDH leakage was reduced in AHA-treated EPEC (400 microg/mL) in both cell lines. Reduced bacterial adherence was observed under light microscopy and altered apoptotic changes were visualized using propidium iodide staining in conjunction with fluorescence microscopy, in both cell lines infected with AHA-treated EPEC and these results were confirmed with transmission electron microscope images. The suppression of type III secretory proteins (TTSPs), EspD ( approximately 40 kDa), was detected in INT 407 cells infected with AHA-treated EPEC. In conclusion, AHA reduces initial bacterial adhesion to intact epithelial cells and it may exert an antiadherence effect against the pathogenesis of EPEC in host epithelial cells. Thus, the investigations provide a rational basis for the treatment of EPEC-mediated diarrhoea with AHA.

Use of specific primers based on the 16S-23S internal transcribed spacer (ITS) region for the screening Bifidobacterium adolescentis in yogurt products and human stool samples

Effective methods for the identification and enumeration of lactic acid producing bacteria (LAB) cells are important for the quality control and assurance of probiotic products. In this study, we designed a polymerase chain reaction (PCR) primer set from the sequence in 16S-23S internal transcribed spacer (ITS) region and used it for the specific detection of Bifidobacterium adolescentis, one of the Bifidobacterium species used in probiotics. Specificity of the PCR primers, i.e., bits-1/bits-2, was assured by assay strains of B. adolescentis, other Bifidobacterium species, and strains of non-Bifidobacterium spp. Coupled with the use of a known primer set specific for Bifidobacterium species, Bifidobacterium strains and B. adolescentis could be identified from LAB strains in fermented dairy products and human fecal samples.

Gaining insight into microbial physiology in the large intestine: a special role for stable isotopes

The importance of the human large intestine for nutrition, health, and disease, is becoming increasingly realized. There are numerous indications of a distinct role for the gut in such important issues as immune disorders and obesity-linked diseases. Research on this long-neglected organ, which is colonized by a myriad of bacteria, is a rapidly growing field that is currently providing fascinating new insights into the processes going on in the colon, and their relevance for the human host. This review aims to give an overview of studies dealing with the physiology of the intestinal microbiota as it functions within and in interaction with the host, with a special focus on approaches involving stable isotopes. We have included general aspects of gut microbial life as well as aspects specifically relating to genomic, proteomic, and metabolomic studies. A special emphasis is further laid on reviewing relevant methods and applications of stable isotope-aided metabolic flux analysis (MFA). We argue that linking MFA with the '-omics' technologies using innovative modeling approaches is the way to go to establish a truly integrative and interdisciplinary approach. Systems biology thus actualized will provide key insights into the metabolic regulations involved in microbe-host mutualism and their relevance for health and disease.

Application of heat-killed bifidobactera in treatment of enterogenic infection caused by dysbacteriosis in mice

AIM: To observe the curative effect of heat-killed bifi-dobactera on dysbacteriosis-induced enterogenic infe-ction in mice.

METHODS: A total of 40 mice were randomly divided into living bacterium group, heat-killed bacterium group, spontaneous recovery group, and normal control group (10 for each). After treatment with the corresponding methods, the serum indexes such as total protein (TP),

albumin (ALB), globulin (GLO), γ-Glutamyl transpepti-dase (GTT), blood urea nitrogen (BUN), lactic dehydro-genase (LDH), creatinine (CER), and tagged bacterium in the homogenate of the mice were detected.

RESULTS: The levels of TP and GLO in the heat-killed bacterium group were significantly increased (71.46±2.01 g/L vs 64.61±2.16 g/L; 35.63±1.57 g/L vs 330.73±1.03 g/L, P < 0.05), while the levels of GGT and BUN were significantly decreased (2.47±0.28 IU/L vs 7.13±1.19 IU/L; 8.32±0.71 mmol/L vs 12.05±0.64 mmol/L, P < 0.01) as compared with those in the spontaneous recovery group. The level of LDH in the heat-killed bac-terium group was significantly decreased as compared with that in the living bacterium group and the normal control group (2 561.23±61.40 vs 2 951.70±155.61, 2 895.27±104.38, P < 0.05). The numbers of the entero-bactera was markedly deceased in the renal, hepatic and pulmonary tissues of the heat-killed bacterium group in comparison with those in the spontaneous recovery group(1.19±0.37, 1.56±0.20, 1.62±0.15 vs 2.17±0.97, 2.42±0.14, 2.20±0.09, P < 0.05 or P < 0.01).

CONCLUSION: The heat-killed bifidobactera are effec-tive in the treatment of enterogenic infection caused by dysbacteriosis in mice, and the effect is the same as that of the living bifidobactera.