Recommendations on probiotics in allergy prevention should not be based on pooling data from different strains

The methodological quality and clinical applicability of meta-analyses on probiotics in 2020: A cross-sectional study

Systematic reviews with meta-analyses (SR/MA) are frequently conducted to investigate clinical efficacy of probiotics. However, only rigorously prepared analyses can serve as the highest level of evidence for a specified research question. We have aimed to determine (1) what is the methodological quality of recent SR/MA conducted to assess the efficacy of probiotics; (2) whether the results of SR/MA have a clinical application; and (3) what are factors associated with better quality and applicability of the SR/MA. We systematically searched 4 databases for SR/MA on the probiotics efficacy published in 2020 (PROSPERO CRD42020222716). The AMSTAR 2 tool and pre-defined authors' criteria were used to evaluate methodological quality and clinical applicability, respectively. A total of 114 SR/MA were appraised. In the case of 88 papers (77%), the overall confidence in the results was rated as "critically low". The most prevalent flaws were lack of list of excluded studies with justification (79.8%), lack of study protocol (60.5%), and problems with appropriate results combination(54.4%). A declaration of conduction a probiotic efficacy SR/MA could have been misleading in case of 18 studies that included also synbiotics, paraprobiotics, and prebiotics trials in analyses. Only 14 SR/MA provided results that can be apply in clinical practice. Higher journal impact factor and European affiliation of the 1st and corresponding authors were most consistently associated with higher odds of AMSTAR 2 items fulfillments. Based on our findings, SR/MA of probiotics trials cannot be treated as the highest level of evidence without a careful evaluation of their methodological validity.

Postnatal probiotics and allergic disease in very preterm infants: Sub-study to the ProPrems randomized trial

BACKGROUND

Probiotic supplementation to mothers and/or their term-born infants has been suggested to prevent allergic disease, in particular eczema; however, no studies have investigated probiotics for prevention of allergic diseases in very preterm infants. We evaluated the effect of a postnatal probiotic combination on development of allergic diseases in very preterm infants.

METHODS

This sub-study was an a priori secondary outcome of the ProPrems multi-center, double-blind, placebo-controlled randomized trial (ANZCTR:12607000144415). ProPrems randomized 1099 very preterm infants to receive a probiotic combination or placebo from soon after birth until discharge from hospital or term corrected age (CA), whichever was earlier. Allergic disease (eczema, atopic eczema, food allergy, wheeze, atopic sensitization) was assessed in a subgroup of ProPrems infants (n = 281) as close to 12 months CA as possible by questionnaire, clinical examination, and skin prick tests to common allergens.

RESULTS

There was no difference in eczema incidence between the probiotic and placebo groups (35[30%] of 118 infants vs 37[27%] of 137 infants, respectively, absolute difference 2.65%, 95% CI -8.45 to 13.75). Similarly, the incidence of atopic eczema (6[5%] of 118 vs 3[2%] of 137), food allergy (4[3%] of 124 vs 2[1%] of 154), wheeze (39[31%] of 127 vs 45[29%] of 154), and atopic sensitization (14[13%] of 106 vs 13[11%] of 123) were similar between the probiotic and placebo groups.

CONCLUSION

This study found no effect of postnatal administration of a probiotic combination on the incidence of allergic diseases or atopic sensitization in the first 2 years of life in children born very preterm. Evidence that probiotics are effective for prevention of allergic disease in premature infants remains lacking; adequately powered randomized controlled trials evaluating probiotic supplementation for allergy prevention in very preterm infants are needed.

The potential for pre-, pro- and synbiotics in the management of infants at risk of cow's milk allergy or with cow's milk allergy: An exploration of the rationale, available evidence and remaining questions

Cow's milk allergy is one of the most commonly reported childhood food allergies, with increasing incidence, persistence and severity in many countries across the world. The World Allergy Organization Special Committee on Food Allergy has identified cow's milk allergy as an area in need of a rationale-based approach in order to make progress against what it considered an onerous problem, with worldwide public health impact. There is growing interest in the potential role of the gut microbiota in the early programming and development of immune responses and allergy. This discussion paper considers the rationale and available evidence for modulation of the gut microbiota and for the use of synbiotics in the management of infants at risk of, or living with cow's milk allergy and summarizes remaining research questions that need to be answered for the development of evidence-based recommendations.

The Role of Probiotics in Preventing Allergic Disease

The prevalence of allergic disorders has been increasing worldwide and significantly impacts the quality of life of the atopic individual. There has been an increased interest in the role of probiotics for the prevention and treatment of allergic disorders, given the recent evidence that atopy risk may be associated with a dysbiosis of the gut microbiome. Research in this area is ongoing with some studies showing possible benefits of probiotics, with seemingly little to no risk. While these studies suggest that there may be a promise in probiotic use for the prevention or treatment of allergy, further evidence is needed to determine its efficacy, optimal dosing, and strains needed for treatment. In this review, we discuss recently published studies examining the benefits, risks, and role of probiotics in preventing atopic dermatitis, asthma, allergic rhinitis, and food allergy.

Altered Gut Microbiota Diversity and Composition in Chronic Urticaria

BACKGROUND

The pathogenesis of chronic urticaria (CU) is closely related to imbalances in immunity. The gastrointestinal microflora provides a vast and continuous stimulation for the immune system. However, the composition and diversity of gut microflora in CU patients are rarely reported.

METHODS

10 CU patients and 10 healthy individuals were selected in this study, and their intestinal microbiome was detected by 16S rRNA sequencing. The data were analyzed using R language software.

RESULTS

392 bacterial OTUs were common in the CU and healthy groups, but there were 159 OTUs particularly existing in the CU group, while 87 OTUs only were observed in healthy individuals. The bacterial diversity was reduced in CU patients compared with healthy individuals. The principal component analysis (PCA) and principal coordinate analysis (PCoA) revealed that the bacterial cluster in CU patients and the healthy controls were divided into different branches. Pathogenic strains including Escherichia coli were significantly higher in CU, while Faecalibacterium prausnitzii, Prevotella copri, and Bacteroides sp. were significantly lower in CU when compared with the healthy controls. CU patients with a high abundance of Escherichia coli had no ideal effect for probiotic therapy.

CONCLUSION

Our results demonstrated that the microbial composition was significantly different between CU patients and the healthy individual, which may be the reason leading to the various outcomes of probiotic treatment.

Effects of oral probiotic supplementation on gut Lactobacillus and Bifidobacterium populations and the clinical status of low-birth-weight preterm neonates: a multicenter randomized, double-blind, placebo-controlled trial

Aim

Probiotic bacteria administered directly after birth to preterm neonates may improve gastrointestinal function and may reduce the incidence of late-onset sepsis, which is a frequent complication in this group.

Purpose

The main objective of this study was to evaluate whether a new probiotic bacterial mixture of Lactobacillus rhamnosus KL53A and Bifidobacterium breve PB04 given to preterm, low-birth-weight neonates would influence composition of their gut microbiota and sepsis rates.

Patients and methods

This study was a multicenter, randomized, double-blind, placebo-controlled trial conducted in clinical centers of neonatal care in Poland. A probiotic or placebo preparation was given twice daily to 181 preterm low-birth-weight neonates who were eligible for enteral feeding between July 2012 and July 2013. The probiotic was given to 90 neonates, while placebo was given to 91 neonates. The gut microbiota was monitored by microbiological analysis of stool samples. Sepsis episodes were detected on the basis of clinical and laboratory findings and confirmed by blood cultures.

Results

Tested probiotic administration resulted in continuous increase of the Lactobacillus and Bifidobacterium counts in the gut microbiota. The applied tested strains successfully colonized the neonates gut since they were present in over 90% of stool samples, which was confirmed by molecular analysis. Regardless of the study group (probiotic or placebo), B. breve colonization correlated with lower staphylococcal sepsis incidence, which was irrespective of whether probiotics were given. No sepsis case caused by strains included in study probiotic was recorded.

Conclusion

Appropriately selected and characterized probiotic bacteria may be safely given to preterm neonates to normalize their distorted gut microbiota and may contribute to lower staphylococcal sepsis rates.

Lactobacillus rhamnosus GG in the Primary Prevention of Eczema in Children: A Systematic Review and Meta-Analysis

Current guidelines recommend the use of probiotics to reduce the risk of eczema. It remains unclear which strain(s) to use. We systematically evaluated data on the efficacy of Lactobacillus rhamnosus GG (LGG) supplementation prenatally and/or postnatally for the primary prevention of eczema. The Cochrane Library, MEDLINE, and EMBASE databases were searched up to August 2018, with no language restrictions, for systematic reviews of randomized controlled trials (RCTs) and RCTs published afterwards. The primary outcome was eczema. For dichotomous outcomes, we calculated the risk ratio (RR) and 95% confidence interval (CI). A random-effects model was used to pool data. Heterogeneity was explored using the I² statistics. The GRADE criteria were used to assess the overall quality of evidence supporting the primary outcome. Seven publications reporting 5 RCTs (889 participants) were included. High to moderate certainty in the body of evidence suggests that LGG supplementation (regardless of the timing of administration) did not reduce the risk of eczema. There was also no consistent effect on other allergic outcomes. This meta-analysis shows that LGG was ineffective in reducing eczema. It does not support the general recommendation to use probiotics for preventing eczema, unless specific strains would be indicated.

Pregnancy outcomes in women taking probiotics or prebiotics: a systematic review and meta-analysis

Background

Probiotics are living microorganisms that, when administered in adequate amounts, confer a health benefit. It has been speculated that probiotics might help prevent preterm birth, but in two previous systematic reviews possible major increases in this risk have been suggested. Our objective was to perform a systematic review and meta-analysis of the risk of preterm birth and other adverse pregnancy outcomes in pregnant women taking probiotics, prebiotics or synbiotics.

Methods

We searched six electronic databases (MEDLINE, EMBASE, CINAHL, Cochrane Central Register of Controlled Trials, Web of Science’s Core collection and BIOSIS Preview) up to September 2016 and contacted authors for additional data. We included randomized controlled trials in which women with a singleton pregnancy received a probiotic, prebiotic or synbiotic intervention. Two independent reviewers extracted data using a piloted form and assessed the risk of bias using the Cochrane risk of bias tool. We used random-effects meta-analyses to pool the results.

Results

We identified 2574 publications, screened 1449 non-duplicate titles and abstracts and read 160 full text articles. The 49 publications that met our inclusion criteria represented 27 studies. No study used synbiotics, one used prebiotics and the rest used probiotics. Being randomized to take probiotics during pregnancy neither increased nor decreased the risk of preterm birth < 34 weeks (RR 1.03, 95% CI 0.29–3.64, I² 0%, 1017 women in 5 studies), preterm birth < 37 weeks (RR 1.08, 95% CI 0.71–1.63, I² 0%, 2484 women in 11 studies), or most of our secondary outcomes, including gestational diabetes mellitus.

Conclusions

We found no evidence that taking probiotics or prebiotics during pregnancy either increases or decreases the risk of preterm birth or other infant and maternal adverse pregnancy outcomes.

Trial registration

We prospectively published the protocol for this study in the PROSPERO database (CRD42016048129).

Electronic supplementary material

The online version of this article (10.1186/s12884-017-1629-5) contains supplementary material, which is available to authorized users.

The maternal microbiome during pregnancy and allergic disease in the offspring

There is substantial epidemiological and mechanistic evidence that the increase in allergic disease and asthma in many parts of the world in part relates to changes in microbial exposures and diet acting via the composition and metabolic products of the intestinal microbiome. The majority of research in this field has focused on the gut microbiome during infancy, but it is increasingly clear that the maternal microbiome during pregnancy also has a key role in preventing an allergy-prone immune phenotype in the offspring. The mechanisms by which the maternal microbiome influences the developing fetal immune system include alignment between the maternal and infant regulatory immune status and transplacental passage of microbial metabolites and IgG. Interplay between microbial stimulatory factors such as lipopolysaccharides and regulatory factors such as short-chain fatty acids may also influence on fetal immune development. However, our understanding of these pathways is at an early stage and further mechanistic studies are needed. There are also no data from human studies relating the composition and metabolic activity of the maternal microbiome during pregnancy to the offspring's immune status at birth and risk of allergic disease. Improved knowledge of these pathways may inform novel strategies for tackling the increase in allergic disorders in the modern world.

Probiotics for the Treatment of Atopic Dermatitis in Children: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Objective: Atopic dermatitis (AD) is a prevalent, burdensome, and psychologically important pediatric concern. Probiotics have been suggested as a treatment for AD. Some reports have explored this topic; however, the utility of probiotics for AD remains to be firmly established.

Methods: To assess the effects of probiotics on AD in children, the PubMed/Medline, Cochrane Library Scopus, and OVID databases were searched for reports published in the English language.

Results: Thirteen studies were identified. Significantly higher SCORAD values favoring probiotics over controls were observed (mean difference [MD], −3.07; 95% confidence interval [CI], −6.12 to −0.03; P < 0.001). The reported efficacy of probiotics in children < 1 year old was −1.03 (95%CI, −7.05 to 4.99) and that in children 1–18 years old was −4.50 (95%CI, −7.45 to −1.54; P < 0.001). Subgroup analyses showed that in Europe, SCORAD revealed no effect of probiotics, whereas significantly lower SCORAD values were reported in Asia (MD, −5.39; 95%CI, −8.91 to −1.87). Lactobacillus rhamnosus GG (MD, 3.29; 95%CI, −0.30 to 6.88; P = 0.07) and Lactobacillus plantarum (MD, −0.70; 95%CI, −2.30 to 0.90; P = 0.39) showed no significant effect on SCORAD values in children with AD. However, Lactobacillus fermentum (MD, −11.42; 95%CI, −13.81 to −9.04), Lactobacillus salivarius (MD, −7.21; 95%CI, −9.63 to −4.78), and a mixture of different strains (MD, −3.52; 95%CI, −5.61 to −1.44) showed significant effects on SCORAD values in children with AD.

Conclusions: Our meta-analysis indicated that the research to date has not robustly shown that probiotics are beneficial for children with AD. However, caution is needed when generalizing our results, as the populations evaluated were heterogeneous. Randomized controlled trials with larger samples and greater power are necessary to identify the species, dose, and treatment duration of probiotics that are most efficacious for treating AD in children.

Protective effect of Bifidobacterium infantis CGMCC313-2 on ovalbumin-induced airway asthma and β-lactoglobulin-induced intestinal food allergy mouse models

AIM

To determine whether oral administration of Bifidobacterium infantis CGMCC313-2 (B. infantis CGMCC313-2) inhibits allergen-induced airway inflammation and food allergies in a mouse model.

METHODS

Ovalbumin (OVA)-induced allergic asthma and β-lactoglobulin-induced food allergy mouse models were used in this study. Following oral administration of B. infantis CGMCC313-2 during or after allergen sensitization, histopathologic changes in the lung and intestine were evaluated by hematoxylin and eosin (HE) staining. In the allergic asthma mouse model, we evaluated the proportion of lung-infiltrating inflammatory cells. OVA-specific IgE and IgG1 levels in serum and cytokine levels in bronchoalveolar lavage fluid (BALF) were also assessed. In the food allergy mouse model, the levels of total IgE and cytokines in serum were measured.

RESULTS

Oral administration of B. infantis CGMCC313-2 during or after allergen sensitization suppressed allergic inflammation in lung and intestinal tissues, while the proportion of infiltrating inflammatory cells was significantly decreased in the BALF of allergic asthma mice. Moreover, B. infantis CGMCC313-2 decreased the serum levels of total IgE in food allergy mice, and reductions in IgE and IgG1 were also observed in OVA-induced allergic asthma mice. The expression of interleukin-4 (IL-4) and IL-13 in both serum and BALF was suppressed following the administration of B. infantis CGMCC313-2, while an effect on serum IL-10 levels was not observed.

CONCLUSION

B. infantis CGMCC313-2 inhibits the secretion of allergen-induced IgE, IL-4 and IL-13, and attenuates allergic inflammation.

Probiotics in Asthma and Allergy Prevention

Interest in probiotic research and its potential benefits in infant foods are relatively recent but significantly increasing. The evolution of the knowledge in the last 20 years demonstrated that alterations in the microbiome may be a consequence of events occurring during infancy or childhood, including prematurity, cesarean section, and nosocomial infections. Several pieces of evidence prove that a "healthy" intestinal microbiota facilitates the development of immune tolerance. Interventional studies suggest that probiotics could be protective against the development of many diseases. Nevertheless, many factors complicate the analysis of dysbiosis in subjects with food allergy. Comparison in-between studies are difficult, because of considerable heterogeneity in study design, sample size, age at fecal collection, methods of analysis of gut microbiome, and geographic location. Currently, there is no positive recommendation from scientific societies to use pre- or probiotics for treatment of food allergy or other allergic manifestations, while their use in prevention is being custom-cleared. However, the recommendation is still based on little evidence. Although there is valid scientific evidence in vitro, there is no sufficient information to suggest the use of specific probiotics in allergy and asthma prevention.

D-tryptophan from probiotic bacteria influences the gut microbiome and allergic airway disease

BACKGROUND

Chronic immune diseases, such as asthma, are highly prevalent. Currently available pharmaceuticals improve symptoms but cannot cure the disease. This prompted demands for alternatives to pharmaceuticals, such as probiotics, for the prevention of allergic disease. However, clinical trials have produced inconsistent results. This is at least partly explained by the highly complex crosstalk among probiotic bacteria, the host's microbiota, and immune cells. The identification of a bioactive substance from probiotic bacteria could circumvent this difficulty.

OBJECTIVE

We sought to identify and characterize a bioactive probiotic metabolite for potential prevention of allergic airway disease.

METHODS

Probiotic supernatants were screened for their ability to concordantly decrease the constitutive CCL17 secretion of a human Hodgkin lymphoma cell line and prevent upregulation of costimulatory molecules of LPS-stimulated human dendritic cells.

RESULTS

Supernatants from 13 of 37 tested probiotic strains showed immunoactivity. Bioassay-guided chromatographic fractionation of 2 supernatants according to polarity, followed by total ion chromatography and mass spectrometry, yielded C₁₁H₁₂N₂O₂ as the molecular formula of a bioactive substance. Proton nuclear magnetic resonance and enantiomeric separation identified D-tryptophan. In contrast, L-tryptophan and 11 other D-amino acids were inactive. Feeding D-tryptophan to mice before experimental asthma induction increased numbers of lung and gut regulatory T cells, decreased lung T_H2 responses, and ameliorated allergic airway inflammation and hyperresponsiveness. Allergic airway inflammation reduced gut microbial diversity, which was increased by D-tryptophan.

CONCLUSIONS

D-tryptophan is a newly identified product from probiotic bacteria. Our findings support the concept that defined bacterial products can be exploited in novel preventative strategies for chronic immune diseases.

Probiotic supplementation can positively affect anxiety and depressive symptoms: a systematic review of randomized controlled trials

Gastrointestinal microbiota, consisting of microbial communities in the gastrointestinal tract, play an important role in digestive, metabolic, and immune functioning. Preclinical studies on rodents have linked behavioral and neurochemical changes in the central nervous system with deficits or alterations in these bacterial communities. Moreover, probiotic supplementation in rodents has been shown to markedly change behavior, with correlated changes in central neurochemistry. While such studies have documented behavioral and mood-related supplementation effects, the significance of these effects in humans, especially in relation to anxiety and depression symptoms, are relatively unknown. Thus, the purpose of this paper was to systematically evaluate current literature on the impact of probiotic supplementation on anxiety and depression symptoms in humans. To this end, multiple databases, including Medline, PsycINFO, PubMed, Scopus, and Web of Science were searched for randomized controlled trials published between January 1990 and January 2016. Search results led to a total of 10 randomized controlled trials (4 in clinically diagnosed and 6 in non-clinical samples) that provided limited support for the use of some probiotics in reducing human anxiety and depression. Despite methodological limitations of the included trials and the complex nature of gut-brain interactions, results suggest the detection of apparent psychological benefits from probiotic supplementation. Nevertheless a better understanding of developmental, modulatory, and metagenomic influences on the GI microbiota, specifically as they relate to mood and mental health, represent strong priorities for future research in this area.