Showing a tremendous metabolic potential, this versatile microbial “organ” exerts a role of primary importance for our metabolism. Recently, the strategic role of the intestinal microbiota in the development, education and functionality of the human innate and adaptive immune system has been recognized [7, 10]. According to Gaboriau-Routhiau et al.[11], specific

members of the intestinal microbial community exert an active role in the modulation of a striking range of T cell functions, such as Th17, Th1, Th2 and regulatory cell phenotype (T regs). Having a profound impact on the overall human immune status, perturbations of the intestinal microbiota have been implicated in the development and progression of this website inflammatory diseases, such as inflammatory bowel diseases (IBD), autoimmune disorders, allergy and type II diabetes [12, 13]. On the basis of the perceived importance of the intestinal microbiota in the education of the human immune

system to tolerance [5], culture-independent perspective studies have been carried out to determine whether specific microbiota dysbioses in the early life could affect the subsequent manifestation and sensitization of atopic diseases. In the Lifestyle and Genetic Constitution (KOALA) Birth Cohort BIRB 796 clinical trial Study – an extensive epidemiological study with involved 957 infants from Netherlands aged 1 month – the presence of Escherichia coli and Clostridium difficile in stools has been associated with a higher risk to develop eczema [14]. Even if the health-promoting Ureohydrolase microbiota components Bifidobacterium and Lactobacillus have been suggested as possible protective

factors against the risk to develop atopy [15, 16], no differences in the prevalence of these probiotic genera between infants with and without allergic disorders have been detected [3, 14, 17, 18]. More recently, two perspective SGC-CBP30 cost surveys of the intestinal microbiota in Danish and Swedish infants have been carried out with a longitudinal approach, sampling the faecal microbiota at different time points during the first year of life [19, 20]. Based on denaturing gradient gel electrophoresis (DGGE) and 16S rDNA 454-pyrosequencing, respectively, these robust and extensive studies proved that the low bacterial diversity in the early life, rather than the prevalence of a specific bacterial taxon, is associated with an increased risk of subsequent atopic disease, reinforcing the “old friend hypothesis” [21]. According to this theory, the western lifestyle caused the disappearance of key bacterial groups from the intestinal microbiota, which are essential to prime the physiology of our immune system. The lack of these “old friends” during the perinatal period led to an immune system incline to inappropriate activation, which is a characteristic of the emerging chronic inflammatory diseases in the western world.