what are probiotics and how do they work?​

The use of probiotics in the prevention or treatment of FA is based on the concept of colonizing the gastro-intestinal tract with health-promoting organisms with positive benefits. Immune-modulation, competitive exclusion, and release of gut mucin secretion, as well as the production of compounds inhibiting the growth of other bacteria have been postulated as mechanisms of action for probiotics [46]. Following encouraging findings from experimental models [47,48], several studies have been designed to examine the efficacy of probiotics in the prevention and/or treatment of FA in humans [49].To investigate the effect of probiotics on the prevention of FA, a double-blind, placebo-controlled trial was performed on pregnant mothers who were either receiving Lactobacillus GG (LGG) or a placebo during the last 4 weeks of pregnancy and during subsequent breastfeeding until the infant reached 3 months of age. When compared to the control group, the probiotic group showed significantly higher serum TGF-β2 levels and a lower incidence in atopic eczema [50]. However, these findings were not replicated in a 4-year follow-up of a randomized placebo-controlled trial, in which both prenatal and postnatal supplementation failed to show any effect on IgE sensitization to food or environmental allergens [51]. Overall, a systematic review and meta-analysis by Zhang et al., evaluating the results of 17 trials involving 2947 infants, concluded that when administered prenatally to the pregnant mother and postnatally to the child, probiotics significantly reduced the risk of atopy (relative risk (RR) 0.78; 95% confidence interval (CI) 0.66–0.92; I2 = 0%). No effects on atopy and food hypersensitivity were recorded when probiotics were administered either prenatally or postnatally [52].With regard to the efficacy of probiotics in food allergy treatment, clinical trials of probiotic supplementation with LGG, combined with extensively hydrolyzed casein formula in milk-allergic children, demonstrated increased rates of milk allergy resolution after 1 [53], 6 [54] and 12 months [55], compared with a control group receiving the formula alone. At follow-up at 1 month, fecal eosinophil cationic protein and tumor necrosis factor-alpha (TNF-a) were significantly decreased in children receiving LGG in their extensively hydrolyzed formula [53]. Also, a clinical resolution was recorded at 6 and 12 months follow-up in the experimental arm compared with control group [54]. However, no differences in the cumulative percentage of tolerance to cow’s milk were reported among groups at 12 months [55]. As the benefits of probiotics were thought to result from their ability to restore the natural balance of gut bacteria, Berni et al. [56] tested this hypothesis by comparing stool from cow’s milk allergic children to that from healthy infants before and after treatment with extensively hydrolyzed formula with or without LGG. The authors noted that the gut microbiome of infants which achieved the immune tolerance was enriched in Blautia and Roseburia and possessed higher concentrations of the short-chain fatty acid butyrate. This led the researchers to hypothesize that probiotics, through modulation of the host–gut ecosystem and, consequently, the local metabolism, work positively to favor the acquisition of ‘tolerance-associated’ microbial profiles [56]. Recently, authors evaluated the baseline presence of Bifidobacterium longum BB536 (BL), Bifidobacterium breve M-16V (BB) and Bifidobacterium infantis M-63 (BI) in children, aged 10–14 months, with an IgE-mediated cow’s milk allergy before, during, and after administration of multi-strain probiotics containing 3.53109 UFC of BL, BB and BI. Following probiotics administration, a significant increase in BI concentration was observed, demonstrating the health-promoting effects of probiotics [57].The rationale for an effect of probiotics on other FA has also been translated on other food allergens, including peanut allergy. The effect of probiotics as an adjuvant to OIT has been evaluated in a double-blind placebo-controlled randomized trial involving a pediatric population (1–10 years) affected by peanut allergy. Co-administration of L. rhamnosus CGMCC1.3724 and peanuts led to sustained desensitization and reduced serum specific IgE levels [58]. These positive effects were maintained over time. A follow-up study 4 years after treatment cessation reported that participants from the probiotic and peanut OIT (PPOIT) group were significantly more likely than those from the placebo group to have continued eating peanuts (p = 0.001), also showing smaller wheals in peanut skin prick tests and significantly higher peanut serum (s)IgG4:sIgE ratios when compared to the placebo [58]. However, due to the lack of individuals in the OIT-only or probiotic-only group, the efficacy attributable to the probiotic remains unclear.The evidence for preventive and therapeutic effects of probiotics on FA in human subjects is still sparse [59,60]. More data are needed to support probiotic supplementation for FA. Regarding the instances where a reduction in clinical symptoms in infants was reported, the effects were not consistent between studies and caution is advised due to methodological aspects, excess losses in patient follow-up, and substantial heterogeneity among included studies in regard to type of strains, duration of treatment, and doses administered [61].

Explain the difference between pre-biotic and pro-biotics in relation to gut health

what might be the cause of clumping of bacteria observed under 40x microscope of probiotic

describe what antibiotics are. What are two ways in which they can work?

describe what a microbiome is.