Deciphering meta-analytic results: a mini-review of probiotics for the prevention of paediatric antibiotic-associated diarrhoea and Clostridium difficile infections

Unique Properties of Yeast Probiotic Saccharomyces boulardii CNCM I-745: A Narrative Review

Probiotics, both bacterial and yeast, have long been associated with a beneficial health history and human well-being. Among yeasts, Saccharomyces is a genus that is efficacious in rendering better human health, with Saccharomyces boulardii (S. boulardii) CNCM I-745 being classified as a probiotic agent. The present review highlights the unique properties of S. boulardii and its rolein the prevention of antibiotic-associated diarrhea (AAD) and pediatric acute gastroenteritis (PAGE) in comparison to bacterial probiotics. Its unique properties,such as viability over a wide pH range, inability to acquire antibiotic resistance genes, and property to achieve a steady state rapidly, have given S. boulardii an edge over bacterial probiotics. In AAD patients, prophylactic use of S. boulardii has shown a significantly lower risk of AAD (in comparison to controls) and restored the diversity of gut microbiota. Among Indian children with PAGE, S. boulardii CNCM I-745 was found superior to Lactobacillus rhamnosus GG and four strains of Bacillus clausii in shortening the duration of diarrhea and reducing the length of hospital stay. S. boulardii CNCM I-745 being considered a safe probiotic for use in children and adults also finds recommendations in several international guidelines for the management of acute diarrhea. The current review discusses evidence for the proven efficacy and safety of S. boulardii CNCM I-745 as a probiotic for preventing gastrointestinal disorders.

Malnutrition and Gut Microbiota in Children

Malnutrition continues to threaten the lives of millions across the world, with children being hardest hit. Although inadequate access to food and infectious disease are the primary causes of childhood malnutrition, the gut microbiota may also contribute. This review considers the evidence on the role of diet in modifying the gut microbiota, and how the microbiota impacts childhood malnutrition. It is widely understood that the gut microbiota of children is influenced by diet, which, in turn, can impact child nutritional status. Additionally, diarrhoea, a major contributor to malnutrition, is induced by pathogenic elements of the gut microbiota. Diarrhoea leads to malabsorption of essential nutrients and reduced energy availability resulting in weight loss, which can lead to malnutrition. Alterations in gut microbiota of severe acute malnourished (SAM) children include increased Proteobacteria and decreased Bacteroides levels. Additionally, the gut microbiota of SAM children exhibits lower relative diversity compared with healthy children. Thus, the data indicate a link between gut microbiota and malnutrition in children, suggesting that treatment of childhood malnutrition should include measures that support a healthy gut microbiota. This could be of particular relevance in sub-Saharan Africa and Asia where prevalence of malnutrition remains a major threat to the lives of millions.

Potential Roles for Probiotics in the Treatment of COVID-19 Patients and Prevention of Complications Associated with Increased Antibiotic Use

Medical care for patients hospitalized with COVID-19 is an evolving process. Most COVID-19 inpatients (58-95%) received empiric antibiotics to prevent the increased mortality due to ventilator-associated pneumonia and other secondary infections observed in COVID-19 patients. The expected consequences of increased antibiotic use include antibiotic-associated diarrhea (AAD) and Clostridioides difficile infections (CDI). We reviewed the literature (January 2020-March 2021) to explore strategies to reduce these consequences. Antimicrobial stewardship programs were effective in controlling antibiotic use during past influenza epidemics and have also been shown to reduce healthcare-associated rates of CDI. Another potential strategy is the use of specific strains of probiotics shown to be effective for the prevention of AAD and CDI prior to the pandemic. During 2020, there was a paucity of published trials using these two strategies in COVID-19 patients, but trials are currently ongoing. A multi-strain probiotic mixture was found to be effective in reducing COVID-19-associated diarrhea in one trial. These strategies are promising but need further evidence from trials in COVID-19 patients.

Temporal development of the infant gut microbiome

The majority of organisms that inhabit the human body reside in the gut. Since babies are born with an immature immune system, they depend on a highly synchronized microbial colonization process to ensure the correct microbes are present for optimal immune function and development. In a balanced microbiome, symbiotic and commensal species outcompete pathogens for resources. They also provide a protective barrier against chemical signals and toxic metabolites. In this targeted review we will describe factors that influence the temporal development of the infant microbiome, including the mode of delivery and gestational age at birth, maternal and infant perinatal antibiotic infusions, and feeding method—breastfeeding versus formula feeding. We will close by discussing wider environmental pressures and early intimate contact, particularly between mother and child, as they play a pivotal role in early microbial acquisition and community succession in the infant.

Probiotics for the prevention of pediatric antibiotic-associated diarrhea

BACKGROUND

Antibiotics alter the microbial balance commonly resulting in antibiotic-associated diarrhea (AAD). Probiotics may prevent AAD via providing gut barrier, restoration of the gut microflora, and other potential mechanisms of action.

OBJECTIVES

The primary objectives were to assess the efficacy and safety of probiotics (any specified strain or dose) used for the prevention of AAD in children.

SEARCH METHODS

MEDLINE, Embase, CENTRAL, CINAHL, and the Web of Science (inception to 28 May 2018) were searched along with registers including the ISRCTN and Clinicaltrials.gov. We also searched the NICE Evidence Services database as well as reference lists from relevant articles.

SELECTION CRITERIA

Randomized, parallel, controlled trials in children (0 to 18 years) receiving antibiotics, that compare probiotics to placebo, active alternative prophylaxis, or no treatment and measure the incidence of diarrhea secondary to antibiotic use were considered for inclusion.

DATA COLLECTION AND ANALYSIS

Study selection, data extraction, and risk of bias assessment were conducted independently by two authors. Dichotomous data (incidence of AAD, adverse events) were combined using a pooled risk ratio (RR) or risk difference (RD), and continuous data (mean duration of diarrhea) as mean difference (MD), along with corresponding 95% confidence interval (95% CI). We calculated the number needed to treat for an additional beneficial outcome (NNTB) where appropriate. For studies reporting on microbiome characteristics using heterogeneous outcomes, we describe the results narratively. The certainty of the evidence was evaluated using GRADE.

MAIN RESULTS

Thirty-three studies (6352 participants) were included. Probiotics assessed included Bacillus spp., Bifidobacterium spp., Clostridium butyricum, Lactobacilli spp., Lactococcus spp., Leuconostoc cremoris, Saccharomyces spp., orStreptococcus spp., alone or in combination. The risk of bias was determined to be high in 20 studies and low in 13 studies. Complete case (patients who did not complete the studies were not included in the analysis) results from 33 trials reporting on the incidence of diarrhea show a precise benefit from probiotics compared to active, placebo or no treatment control.After 5 days to 12 weeks of follow-up, the incidence of AAD in the probiotic group was 8% (259/3232) compared to 19% (598/3120) in the control group (RR 0.45, 95% CI 0.36 to 0.56; I² = 57%, 6352 participants; NNTB 9, 95% CI 7 to 13; moderate certainty evidence). Nineteen studies had loss to follow-up ranging from 1% to 46%. After making assumptions for those lost, the observed benefit was still statistically significant using an extreme plausible intention-to-treat (ITT) analysis, wherein the incidence of AAD in the probiotic group was 12% (436/3551) compared to 19% (664/3468) in the control group (7019 participants; RR 0.61; 95% CI 0.49 to 0.77; P <0.00001; I² = 70%). An a priori available case subgroup analysis exploring heterogeneity indicated that high dose (≥ 5 billion CFUs per day) is more effective than low probiotic dose (< 5 billion CFUs per day), interaction P value = 0.01. For the high dose studies the incidence of AAD in the probiotic group was 8% (162/2029) compared to 23% (462/2009) in the control group (4038 participants; RR 0.37; 95% CI 0.30 to 0.46; P = 0.06; moderate certainty evidence). For the low dose studies the incidence of AAD in the probiotic group was 8% (97/1155) compared to 13% (133/1059) in the control group (2214 participants; RR 0.68; 95% CI 0.46 to 1.01; P = 0.02). Again, assumptions for loss to follow-up using an extreme plausible ITT analysis was statistically significant. For high dose studies the incidence of AAD in the probiotic group was 13% (278/2218) compared to 23% (503/2207) in control group (4425 participants; RR 0.54; 95% CI 0.42 to 0.70; P <0.00001; I² = 68%; moderate certainty evidence).None of the 24 trials (4415 participants) that reported on adverse events reported any serious adverse events attributable to probiotics. Adverse event rates were low. After 5 days to 4 weeks follow-up, 4% (86/2229) of probiotics participants had an adverse event compared to 6% (121/2186) of control participants (RD 0.00; 95% CI -0.01 to 0.01; P < 0.00001; I² = 75%; low certainty evidence). Common adverse events included rash, nausea, gas, flatulence, abdominal bloating, and constipation.After 10 days to 12 weeks of follow-up, eight studies recorded data on our secondary outcome, the mean duration of diarrhea; with probiotics reducing diarrhea duration by almost one day (MD -0.91; 95% CI -1.38 to -0.44; P <0.00001; low certainty evidence). One study reported on microbiome characteristics, reporting no difference in changes with concurrent antibiotic and probiotic use.

AUTHORS' CONCLUSIONS

The overall evidence suggests a moderate protective effect of probiotics for preventing AAD (NNTB 9, 95% CI 7 to 13). Using five criteria to evaluate the credibility of the subgroup analysis on probiotic dose, the results indicate the subgroup effect based on high dose probiotics (≥ 5 billion CFUs per day) was credible. Based on high-dose probiotics, the NNTB to prevent one case of diarrhea is 6 (95% CI 5 to 9). The overall certainty of the evidence for the primary endpoint, incidence of AAD based on high dose probiotics was moderate due to the minor issues with risk of bias and inconsistency related to a diversity of probiotic agents used. Evidence also suggests that probiotics may moderately reduce the duration of diarrhea, a reduction by almost one day. The benefit of high dose probiotics (e.g. Lactobacillus rhamnosus orSaccharomyces boulardii) needs to be confirmed by a large well-designed multi-centered randomized trial. It is premature to draw firm conclusions about the efficacy and safety of 'other' probiotic agents as an adjunct to antibiotics in children. Adverse event rates were low and no serious adverse events were attributable to probiotics. Although no serious adverse events were observed among inpatient and outpatient children, including small studies conducted in the intensive care unit and in the neonatal unit, observational studies not included in this review have reported serious adverse events in severely debilitated or immuno-compromised children with underlying risk factors including central venous catheter use and disorders associated with bacterial/fungal translocation.

Pre-colonization with the commensal fungus Candida albicans reduces murine susceptibility to Clostridium difficile infection

Clostridium difficile is a major nosocomial pathogen responsible for close to half a million infections and 27,000 deaths annually in the U.S. Preceding antibiotic treatment is a major risk factor for C. difficile infection (CDI) leading to recognition that commensal microbes play a key role in resistance to CDI. Current antibiotic treatment of CDI is only partially successful due to a high rate of relapse. As a result, there is interest in understanding the effects of microbes on CDI susceptibility to support treatment of patients with probiotic microbes or entire microbial communities (e.g., fecal microbiota transplantation). The results reported here demonstrate that colonization with the human commensal fungus Candida albicans protects against lethal CDI in a murine model. Colonization with C. albicans did not increase the colonization resistance of the host. Rather, our findings showed that one effect of C. albicans colonization was to enhance a protective immune response. Mice pre-colonized with C. albicans expressed higher levels of IL-17A in infected tissue following C. difficile challenge compared to mice that were not colonized with C. albicans. Administration of cytokine IL-17A was demonstrated to be protective against lethal murine CDI in mice not colonized with C. albicans. C. albicans colonization was associated with changes in the abundance of some bacterial components of the gut microbiota. Therefore, C. albicans colonization altered the gut ecosystem, enhancing survival after C. difficile challenge. These findings demonstrate a new, beneficial role for C. albicans gut colonization.

Probiotic use in an infectious disease setting

INTRODUCTION

The lethality of infectious diseases and deep concern over growing antimicrobial resistance make it essential that alternative or adjunct therapies be developed. Areas covered: Using papers published in PubMed, a case is presented to consider beneficial microbes as a means to improve management of infectious diseases. Clinical evidence is mounting that certain probiotic microbes can contribute to this armamentarium. These could have an immediate effect against necrotizing enterocolitis, pre- and post-surgical procedures, antibiotic-associated infections, urogenital infections in women and for reducing the severity and duration of respiratory infections. While further studies will always be warranted irrespective of the intervention, and quality assurance and patient safety must remain a priority, the main barrier to implementation may well be unwarranted hesitation amongst physicians, healthcare administrators and regulators. Meanwhile, patients are already taking things into their own hands at a time when their knowledge of product selection is poor and clinical guidance is invariably missing. Expert commentary: Until vaccines and other alternatives emerge, it would be foolhardy to not use best practices to bring probiotics into mainstream infectious disease management. Our ability to manipulate microbial-host interactions offers hope before the last antibiotic stops being effective.

The role of early life nutrition in the establishment of gastrointestinal microbial composition and function

The development of the human infant intestinal microbiota is a sequential process that begins in utero and continues during the first 2 to 3 years of life. Microbial composition and diversity are shaped by host genetics and multiple environmental factors, of which diet is a principal contributor. An understanding of this process is of clinical importance as the microbiota acquired in early life influence gastrointestinal, immune and neural development, and reduced microbial diversity or dysbiosis during infancy is associated with disorders in infancy and later childhood. The goal of this article was to review the published literature that used culture-independent methods to describe the development of the gastrointestinal microbiota in breast- and formula-fed human infants as well as the impact of prebiotic and probiotic addition to infant formula, and the addition of solid foods.

Importance of Molecular Methods to Determine Whether a Probiotic is the Source of Lactobacillus Bacteremia

There has been an increasing interest in the use of probiotic products for the prevention of Clostridium difficile infection (CDI). Bio-K+(®) is a commercial probiotic product comprising three strains of lactobacilli--Lactobacillus acidophilus CL1285(®), Lact. casei LBC80R(®) and Lact. rhamnosus CLR2(®)--that have been applied to prevent CDI. Generally considered as safe, lactobacilli have potential to cause bacteremia, endocarditis and other infections. The source of Lactobacillus bacteremia can be normal human flora or lactobacilli-containing probiotic. The aim of this study was to assess whether probiotic lactobacilli caused bacteremia and to show the value of molecular identification and typing techniques to determine probiotic and patient strain relatedness. We report an episode of Lactobacillus bacteremia in a 69-year-old man admitted to a hospital with severe congestive heart failure. During his hospitalization, he required long-term antibiotic therapy. Additionally, the patient received Bio-K+(®) probiotic as part of a quality improvement project to prevent CDI. Subsequently, Lactobacillus bacteremia occurred. Two independent blinded laboratory evaluations, using pulse field gel electrophoresis, 16S rRNA gene sequencing and DNA fingerprint analysis (rep-PCR), were performed to determine whether the recovered Lact. acidophilus originated from the probiotic product. Ultimately, the patient strain was identified as Lact. casei and both laboratories found no genetic relation between the patient's strain and any of the probiotic lactobacilli. This clinical case of lactobacillus bacteremia in the setting of probiotic exposure demonstrates the value of using discriminatory molecular methods to clearly determine whether there were a link between the patient's isolate and the probiotic strains.

Systematic review and meta-analysis: Multi-strain probiotics as adjunct therapy for Helicobacter pylori eradication and prevention of adverse events

BACKGROUND

Eradication rates with triple therapy for Helicobacter pylori infections have currently declined to unacceptable levels worldwide. Newer quadruple therapies are burdened with a high rate of adverse events. Whether multi-strain probiotics can improve eradication rates or diminish adverse events remains uncertain.

METHODS

Relevant publications in which patients with H. pylori infections were randomized to a multi-strain probiotic or control were identified in PubMed, Cochrane Databases, and other sources from 1 January 1960-3 June 2015. Primary outcomes included eradication rates, incidence of any adverse event and the incidence of antibiotic-associated diarrhea. As probiotic efficacy is strain-specific, pooled relative risks and 95% confidence intervals were calculated using meta-analysis stratified by similar multi-strain probiotic mixtures.

RESULTS

A total of 19 randomized controlled trials (20 treatment arms, n = 2730) assessing one of six mixtures of strains of probiotics were included. Four multi-strain probiotics significantly improved H. pylori eradication rates, five significantly prevented any adverse reactions and three significantly reduced antibiotic-associated diarrhea. Only two probiotic mixtures (Lactobacillus acidophilus/Bifidobacterium animalis and an eight-strain mixture) had significant efficacy for all three outcomes.

CONCLUSIONS

Our meta-analysis found adjunctive use of some multi-strain probiotics may improve H. pylori eradication rates and prevent the development of adverse events and antibiotic-associated diarrhea, but not all mixtures were effective.

Systematic review with meta-analysis: Lactobacillus rhamnosus GG in the prevention of antibiotic-associated diarrhoea in children and adults

BACKGROUND

The effects of probiotics are strain specific. The clinical effects of each strain need to be evaluated separately.

AIM

To evaluate the efficacy of Lactobacillus rhamnosus GG (LGG) in the prevention of antibiotic-associated diarrhoea (AAD) in children and adults.

METHODS

The Cochrane Library, MEDLINE, and EMBASE databases were searched up to July 2015, with no language restrictions, for randomised controlled trials (RCTs). Reference lists of reviews and included studies were examined. The quality of evidence (QoE) was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) guidelines.

RESULTS

Twelve RCTs (1499 participants) were included. Treatment with LGG compared with placebo or no additional treatment reduced the risk of AAD in patients treated with antibiotics from 22.4% to 12.3% (11 RCTs, n = 1308, relative risk, RR: 0.49, 95% confidence interval, CI: 0.29-0.83, low QoE). However, when children and adults were evaluated separately, the difference was significant in children only (five RCTs, n = 445, RR 0.48, 95% CI 0.26-0.89; moderate QoE). In adults, the difference was not significant (six RCTs, n = 863, RR 0.48, 95% CI 0.20-1.15; low QoE), except for in a subset of patients receiving antibiotics as part of Helicobacter pylori eradication therapy (four RCTs, n = 280, RR 0.26, 95% CI 0.11-0.59; low QoE).

CONCLUSIONS

This meta-analysis shows that Lactobacillus rhamnosus GG is effective in preventing antibiotic-associated diarrhoea in children and adults treated with antibiotics for any reason. However, the quality of evidence is moderate to low.

Flow cytometry as an auxiliary tool for the selection of probiotic bacteria

Selection of appropriate bacterial strains is crucial for development of new probiotic preparations. The fundamental prerequisite for potential efficacy of a probiotic preparation for oral application is the selection of appropriate bacterial strains with good gastrointestinal colonisation abilities, antimicrobial activity, and tolerance of conditions in the gastrointestinal tract, resistance to different antimicrobial agents, survival during processing and storage. The strain should be genetically stable, it should have good growth properties, to maintain its high viability at processing and when in storage. Mostly, the properties of promising strains are tested in the first phase in vitro, and only the best ones undergo subsequent in vivo testing. in vitro tests are often performed by classical microbiological cultivation methods which are material and time consuming, and they are not able to distinguish between ‘viable but nonculturable’ and dead bacteria. Flow cytometry is usually used for counting, phenotyping or functional characterisation of immune cells. Nowadays, flow cytometry is increasingly used in microbiology for counting bacteria, determining their viability and metabolic activity, detecting specific strains or testing their adherence abilities. The utilisation of flow cytometry in combination with an appropriate fluorescent labelling represents an effective and rapid method for the selection of probiotic bacteria.

Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea

BACKGROUND

Antibiotic-associated diarrhoea is a common complication of antibiotic use, but it can be prevented with administration of probiotics.

AIM

To update our 2005 meta-analysis on the effectiveness of Saccharomyces boulardii in preventing antibiotic-associated diarrhoea in children and adults.

METHODS

The Cochrane Library, MEDLINE, and EMBASE databases were searched up until May 2015, with no language restrictions, for randomised controlled trials; additional references were obtained from reviewed articles. The quality of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) guidelines.

RESULTS

Twenty-one randomised controlled trials (4780 participants), among which 16 were new trials, met the inclusion criteria for this updated systematic review. Administration of S. boulardii compared with placebo or no treatment reduced the risk of antibiotic-associated diarrhoea (as defined by the study investigators) in patients treated with antibiotics from 18.7% to 8.5% (risk ratio, RR: 0.47; 95% CI: 0.38-0.57, number needed to treat, NNT: 10; 95% CI: 9-13). In children, S. boulardii reduced the risk from 20.9% to 8.8% (6 randomised controlled trials, n=1653, RR: 0.43, 95% CI: 0.3-0.6); in adults, from 17.4% to 8.2% (15 randomised controlled trials, n=3114, RR: 0.49, 95% CI: 0.38-0.63). Moreover, S. boulardii reduced the risk of Clostridium difficile-associated diarrhoea; however, this reduction was significant only in children (2 randomised controlled trials, n = 579, RR: 0.25; 95% CI: 0.08-0.73) and not in adults (9 randomised controlled trials, n = 1441, RR: 0.8, 95% CI: 0.47-1.34).

CONCLUSIONS

This meta-analysis confirms that S. boulardii is effective in reducing the risk of antibiotic-associated diarrhoea in children and adults.

Application of meta-analysis to specific research fields: Lessons learned

Scientific research is challenged to translate findings from multiple, often conflicting, clinical trials into a simple answer of whether a treatment works or not. The public and healthcare providers alike frequently voice their frustrations when the media reports a treatment working on one day, but seemingly the next day reports a study refuting the previous one. Meta-analyses are being used more commonly by researchers to convey an understandable summary of scientific studies to the general public and healthcare providers. As time goes by, we have learned how to improve meta-analytic techniques to reflect more valid results and when it is appropriate to pool or not to pool results from different studies. Retrospective reviews often don’t acknowledge this learning curve and may fail to recommend the most current valid guidelines. This editorial presents an example of how the current use of meta-analysis has shifted in one field (the therapeutic effects of probiotics) and recommendations on how to correctly interpret the results of such an analysis.

Progress and challenges in developing metabolic footprints from diet in human gut microbial cometabolism

Homo sapiens harbor trillions of microbes, whose microbial metagenome (collective genome of a microbial community) using omic validation interrogation tools is estimated to be at least 100-fold that of human cells, which comprise 23,000 genes. This article highlights some of the current progress and open questions in nutrition-related areas of microbiome research. It also underscores the metabolic capabilities of microbial fermentation on nutritional substrates that require further mechanistic understanding and systems biology approaches of studying functional interactions between diet composition, gut microbiota, and host metabolism. Questions surrounding bacterial fermentation and degradation of dietary constituents (particularly by Firmicutes and Bacteroidetes) and deciphering how microbial encoding of enzymes and derived metabolites affect recovery of dietary energy by the host are more complex than previously thought. Moreover, it is essential to understand to what extent the intestinal microbiota is subject to dietary control and to integrate these data with functional metabolic signatures and biomarkers. Many lines of research have demonstrated the significant role of the gut microbiota in human physiology and disease. Probiotic and prebiotic products are proliferating in the market in response to consumer demand, and the science and technology around these products are progressing rapidly. With high-throughput molecular technologies driving the science, studying the bidirectional interactions of host-microbial cometabolism, epithelial cell maturation, shaping of innate immune development, normal vs. dysfunctional nutrient absorption and processing, and the complex signaling pathways involved is now possible. Substantiating the safety and mechanisms of action of probiotic/prebiotic formulations is critical. Beneficial modulation of the human microbiota by using these nutritional and biotherapeutic strategies holds considerable promise as next-generation drugs, vaccinomics, and metabolic agents and in novel food discovery.

Foreword: All things considered about probiotics, prebiotics and ıntestinal microbiota in children – from bench to bedside

There are numerorus published and ongoing experimental/clinical studies about probiotics and prebiotics, intestinal microbiota and nutrition. Three years ago, at the first International Symposium of Probiotics Prebiotics in Paediatrics in Istanbul (2012) we highlighted the ‘paediatric perspective’ on these issues and brought together more than 40 global key opinion leaders and 400 attendants to have a chance to extensively discuss the past, present and the future. In 2014, the second state of art congress, held in Antalya, aimed to discuss the gut microbiota and microbiotics and their impact through lifespan. Selected papers of this conference are presented in this special issue ‘prebiotics and probiotics in paediatrics’ of Beneficial Microbes. A summary of the conference results is provided below.