Evidence suggests that possible imbalances in intestinal microbiota composition may be implicated in the occurrence of allergic diseases. Although several studies published until 2006 indicated a correlation between microbiota composition and allergic symptoms, it has not been possible to distinguish protective microorganisms from those associated with increased risk of allergic diseases. Therefore, the objective of this study was to review the studies published since 2007 that address the intestinal microbiota in allergic diseases. Twenty-one studies were identified after excluding those that performed a clinical intervention before stool collection. In the early microbiota of children who later developed allergies, lower bacterial diversity was observed, with a predominance of Firmicutes; a higher count of Bacteroidaceae; a higher prevalence of the anaerobic bacteria Bacteroides fragilis, Escherichia coli, Clostridium difficile, Bifidobacterium catenulatum, Bifidobacterium bifidum, and Bifidobacterium longum; and a lower prevalence of Bifidobacterium adolescentis, B. bifidum, and Lactobacillus. In the microbiota of allergic children whose intestinal microbiota was assessed at the onset of allergic symptoms, there was a higher count of Bacteroides; a lower count of Akkermansia muciniphila, Faecalibacterium prausnitzii, and Clostridium; a higher prevalence of B. adolescentis; a lower prevalence of B. catenulatum and Staphylococcus aureus; and a lower bacterial diversity.

Constipation often begins in the first year of life. The aim of this study was to assess the effect of fructooligosaccharides (FOS) in the treatment of infants with constipation. This randomized, double-blind, placebo-controlled clinical trial included infants with constipation who were randomly assigned to one of two parallel groups: FOS or placebo. Either the FOS supplement or the placebo was added to the infant formula. Thirty-six infants completed the 4-week intervention. Therapeutic success occurred in 83.3% of the FOS group infants and in 55.6% of the control group infants (p = 0.073; one-tailed test). Compared with the control group, the FOS group exhibited a higher frequency of softer stools (p = 0.035) and fewer episodes of straining and/or difficulty passing stools (p = 0.041). At the end of the intervention, the mouth-to-anus transit time was shorter (22.4 and 24.5 h, p = 0.035), and the Bifidobacterium sp. count was higher (p = 0.006) in the FOS group. In conclusion, the use of FOS in infants with constipation was associated with significant improvement in symptoms, but the results showed no statistical significance regarding the success of the therapy compared with the control group. FOS was associated with reduced bowel transit time and higher counts of the genus Bifidobacterium in the stool.

This study evaluated the breath CH₄excretion and concentration ofM. smithiiin intestinal microbiota of schoolchildren from 2 slums. One hundred and eleven children from a slum near a sanitary landfill, 35 children of a slum located away from the sanitary landfill, and 32 children from a high socioeconomic level school were included in the study. Real-time PCR was performed to quantify theM. smithii nifHgene and it was present in the microbiota of all the participating children, with higherP<0.05concentrations in those who lived in the slum near the landfill (3.16×107 CFU/g of feces), comparing with the children from the slum away from the landfill (2.05×106 CFU/g of feces) and those from the high socioeconomic level group (3.93×105 CFU/g of feces). The prevalence of children who present breath methane was 53% in the slum near the landfill, 31% in the slum further away from the landfill and, 22% in the high socioeconomic level group. To live near a landfill is associated with higher concentrations ofM. smithiiin intestinal microbiota, comparing with those who live away from the landfill, regardless of their socioeconomics conditions.

Breast milk is rich in bioactive components, especially human milk oligosaccharides (HMOs), which are crucial for establishing gut microbiota. The 2′-FL (2-Fucosyllactose), one of the most abundant oligosaccharides in breast milk, functions as a selective prebiotic. Objective: To examine the effect of adding 2′-FL (2-Fucosyllactose) to an infant formula containing prebiotic galacto-oligosaccharides (GOSs) and fructo-oligosaccharides (FOSs) on the gut microbiome of healthy formula-fed infants. Methods: This study enrolled infants from three groups: an HMO experimental group (n = 29), a GOS/FOS control group (n = 30), and an exclusively breastfed (breast milk [BM]) reference group (n = 28). Fecal samples from the three groups in the first and fourth months of life were analyzed. The V3 and V4 regions of the 16S rRNA gene were amplified and sequenced on the Illumina MiSeq. ANOVA, Kruskal–Wallis, richness indices (Chao1, Shannon), UniFrac distances, and the Adonis tests were used to perform statistical analyses on the relative abundance of phyla and genera, as well as the alpha and beta-diversity of the gut microbiota. Results: After intervention, Actinobacteriota emerged as the predominant phylum in both the HMO (60.4%) and BM (46.6%) groups. Bifidobacterium and Escherichia-Shigella were identified as the two most abundant bacterial genera in both groups. Nevertheless, the statistical analysis showed that the relative abundance of Bifidobacterium in the HMO formula-fed group after intervention was similar to that in the BM group (p > 0.05). Infants in the HMO and GOS/FOS groups showed higher relative abundance of [Ruminococcus]_gnavus_group bacteria compared to those in the BM group. Groups fed with infant formula demonstrated higher alpha-diversity of gut microbiota compared to breastfed infants (p < 0.05), at the time of admission as well as after the intervention. Beta-diversity was significantly different among the three groups, according to type of feeding. Infants fed a 2′-FL-supplemented infant formula exhibited growth comparable to that of breastfed infants throughout the intervention period, demonstrating that the formula was both safe and well tolerated. Conclusions: Adding 2′-FL to an infant formula containing 4 g/L of GOS + FOS resulted in a stronger bifidogenic effect compared to the formula without 2′-FL.