Establishment of the bacterial fecal community during the first month of life in Brazilian newborns

OBJECTIVE:

The establishment of the intestinal microbiota in newborns is a critical period with possible long-term consequences for human health. In this research, the development of the fecal microbiota of a group of exclusively breastfed neonates living in low socio-economic conditions in the city of São Paulo, Brazil, during the first month of life, was studied.

METHODS:

Fecal samples were collected from ten neonates on the second, seventh, and 30^th days after birth. One of the neonates underwent antibiotic therapy. Molecular techniques were used for analysis; DNA was extracted from the samples, and 16S rRNA libraries were sequenced and phylogenetically analyzed after construction. A real-time polymerase chain reaction (PCR) was performed on the samples taken from the 30^th day to amplify DNA from Bifidobacterium sp.

RESULTS:

The primary phylogenetic groups identified in the samples were Escherichia and Clostridium. Staphylococcus was identified at a low rate. Bifidobacterium sp. was detected in all of the samples collected on the 30^th day. In the child who received antibiotics, a reduction in anaerobes and Escherichia, which was associated with an overgrowth of Klebsiella, was observed throughout the experimental period.

CONCLUSION:

The observed pattern of Escherichia predominance and reduced Staphylococcus colonization is in contrast with the patterns observed in neonates living in developed countries.     

Gut microbiota and probiotics in colon tumorigenesis

The human gastrointestinal tract harbors a complex and abundant microbial community reaching as high as 10¹³–10¹⁴ microorganisms in the colon. This endogenous microbiota forms a symbiotic relationship with their eukaryotic host and this close partnership helps maintain homeostasis by performing essential and non-redundant tasks (e.g. nutrition/energy and, immune system balance, pathogen exclusion). Although this relationship is essential and beneficial to the host, various events (e.g. infection, diet, stress, inflammation) may impact microbial composition, leading to the formation of a dysbiotic microbiota, further impacting on health and disease states. For example, Crohn’s disease and ulcerative colitis, collectively termed inflammatory bowel diseases (IBD), have been associated with the establishment of a dysbiotic microbiota. In addition, extra-intestinal disorders such as obesity and metabolic syndrome are also associated with the development of a dysbiotic microbiota. Consequently, there is an increasing interest in harnessing the power of the microbiome and modulating its composition as a means to alleviate intestinal pathologies/disorders and maintain health status. In this review, we will discuss the emerging relationship between the microbiota and development of colorectal cancer as well as present evidence that microbial manipulation (probiotic, prebiotic) impacts disease development.     

Dysbiosis of Gut Microbiota (DOGMA)--a novel theory for the development of Polycystic Ovarian Syndrome

Polycystic Ovarian Syndrome (PCOS) is the most common cause for menstrual disturbance and impaired ovulation, effecting one in twenty women of reproductive age. As the majority of women with PCOS are either overweight or obese, a dietary or adipose tissue related trigger for the development of the syndrome is quite possible. It has now well established that PCOS is characterised by a chronic state of inflammation and insulin resistance, but the precise underlying triggers for these two key biochemical disturbances is presently unknown. In this paper we present support for a microbiological hypothesis for the development of PCOS. This novel paradigm in PCOS aetiology suggests that disturbances in bowel bacterial flora ("Dysbiosis of Gut Microbiota") brought about by a poor diet creates an increase in gut mucosal permeability, with a resultant increase in the passage of lipopolysaccaride (LPS) from Gram negative colonic bacteria into the systemic circulation. The resultant activation of the immune system interferes with insulin receptor function, driving up serum insulin levels, which in turn increases the ovaries production of androgens and interferes with normal follicle development. Thus, the Dysbiosis of Gut Microbiota (DOGMA) theory of PCOS can account for all three components of the syndrome-anovulation/menstrual irregularity, hyper-androgenism (acne, hirsutism) and the development of multiple small ovarian cysts.     

Toll-like receptor 4 is protective against neonatal murine ischemia-reperfusion intestinal injury

Purpose

Premature infants receiving probiotics have a decreased incidence of necrotizing enterocolitis. This may be mediated by intestinal bacterial signaling via toll-like receptors (TLRs) 2 and 4 maintaining intestinal homeostasis. We hypothesized that TLRs 2 and 4 are protective against ischemia-reperfusion (I/R) intestinal injury.

Methods

Two-week-old C57BL/6 wild-type (WT), B6.TLR2^−/−, B6.TLR4^−/−, B6.TLR2^−/−4^−/−, and microbially reduced (antibiotic-treated) mice (MR) underwent 60 minutes of superior mesenteric artery occlusion (I) followed by 90 minutes of reperfusion (R). Small intestine was harvested for analysis of microscopic injury, apoptosis, and inflammatory gene expression using quantitative polymerase chain reaction.

Results

After I/R, the median histologic injury scores of the B6.TLR4^−/−, B6.TLR2^−/−4^−/−, and MR pups were higher than the WT or B6.TLR2^−/− pups that corresponded with greater apoptosis based on terminal deoxynucleotidyl transferase-mediated dUTP-FITC nick-end labeling and activated caspase-3 immunostaining. B6.TLR4^−/−, B6.TLR2^−/−4^−/−, and MR also had elevated tissue innate immunity-associated chemokine and cytokine expression.

Conclusions

Neonatal mice deficient in TLR4, either alone or also deficient in TLR2, as well as those lacking a normal commensal intestinal microbiome are more susceptible to an I/R model of intestinal injury. These results may provide a mechanism for commensal bacterial-mediated protection, which may help to direct further studies to elucidate the mechanism of probiotic protection.     

The intestinal microbiota and inflammatory bowel disease

The intestine hosts a complex ecosystem of microbial communities. Experimental data suggests that the microbiota has metabolic functions that contribute to nutrient and energy recovery from non-digestible substrates. Moreover, microbial colonization is essential for the normal development of the immune system and therefore seems to influence homeostasis between environmental antigen load and immune response. In genetically-susceptible individuals, an imbalance may give rise to diseases of immune dysregulation, including chronic inflammatory bowel diseases, in which there is an exaggerated immune response to harmless microbial antigens. Despite the availability of new molecular technologies, the normal composition of the human intestinal microbiota remains unknown. In the next few years, the results of international projects designed to determine the precise impact of the microbiota in various physiological and pathological processes will hopefully lead to major advances.     

Environmental influences on T regulatory cells in inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterized by chronic, idiopathic inflammation of the intestine. The disease is thought to result from a combination of genetic and environmental factors which ultimately leads to a mucosal immune system that overreacts to normal constituents of the mucosal microbiota. The inflammation in IBD is primarily mediated by inappropriate production of proinflammatory cytokines by CD4(+) T effector cells, effects that are suppressed by CD4(+) T regulatory cells. Defects in both the function of T regulatory cells, and the ability of T effector cells to be suppressed, have been implicated in IBD. In this review we will discuss environmental factors, including cytokines, vitamins A and D, and commensal bacteria, which influence the phenotype and function of regulatory T cells and thereby alter the course of IBD. We will also discuss how these environmental signals can be manipulated therapeutically in order to improve the function of regulatory T cells and ultimately restore mucosal homeostasis in patients with IBD.     

Negative regulation of Toll-like receptor signaling plays an essential role in homeostasis of the intestine

A healthy intestinal tract is characterized by controlled homeostasis due to the balanced interaction between commensal bacteria and the host mucosal immune system. Human and animal model studies have supported the hypothesis that breakdown of this homeostasis may underlie the pathogenesis of inflammatory bowel diseases. However, it is not well understood how intestinal microflora stimulate the intestinal mucosal immune system and how such activation is regulated. Using a spontaneous, commensal bacteria-dependent colitis model in IL-10-deficient mice, we investigated the role of TLR and their negative regulation in intestinal homeostasis. In addition to IL-10(-/-) MyD88(-/-) mice, IL-10(-/-) TLR4(-/-) mice exhibited reduced colitis compared to IL-10(-/-) mice, indicating that TLR4 signaling plays an important role in inducing colitis. Interestingly, the expression of IRAK-M, a negative regulator of TLR signaling, is dependent on intestinal commensal flora, as IRAK-M expression was reduced in mice re-derived into a germ-free environment, and introduction of commensal bacteria into germ-free mice induced IRAK-M expression. IL-10(-/-) IRAK-M(-/-) mice exhibited exacerbated colitis with increased inflammatory cytokine gene expression. Therefore, this study indicates that intestinal microflora stimulate the colitogenic immune system through TLR and negative regulation of TLR signaling is essential in maintaining intestinal homeostasis.     

肠道菌群对免疫系统影响的研究进展

【摘要】〓肠道菌群是机体的重要组成部分,与免疫系统的关系十分密切。肠道微生物可以对免疫系统,包括全身性的固有免疫、特异性免疫甚至自身免疫疾病产生影响。来自于机体内外的理化刺激和生物刺激会打破正常菌群与人体之间的动态平衡,菌群数量和种类的改变都会导致肠道内菌群的紊乱,多项研究表明,肠道菌群紊乱可能在多种免疫疾病的形成中起着重要作用。