The bidirectional relationship between the gut microbiota and the nervous system is known as the microbiota–gut–brain axis (MGBA). The MGBA controls the complex interactions between the brain, the enteric nervous system, the gut-associated immune system, and the enteric neuroendocrine systems, regulating key physiological functions such as the immune response, sleep, emotions and mood, food intake, and intestinal functions. Psychobiotics are considered tools with the potential to modulate the MGBA through preventive, adjunctive, or curative approaches, but their specific mechanisms of action on many aspects of health are yet to be characterized. This narrative review and perspectives article highlights the key paradigms needing attention as the scope of potential probiotics applications in human health increases, with a growing body of evidence supporting their systemic beneficial effects. However, there are many limitations to overcome before establishing the extent to which we can incorporate probiotics in the management of neuropsychiatric disorders. Although this article uses the term probiotics in a general manner, it remains important to study probiotics at the strain level in most cases.

A probiotic formulation combining Lactobacillus helveticus Rosell^®-52, Bifidobacterium infantis Rosell^®-33, and Bifidobacterium bifidum Rosell^®-71 with fructooligosaccharides, first commercialized in China, has been sold in over 28 countries since 2002. Clinical studies with this blend of strains were conducted mainly in pediatric populations, and most were published in non-English journals. This comprehensive review summarizes the clinical studies in infants and children to evaluate the efficacy of this probiotic for pediatric indications. Literature searches for pediatric studies on Biostime^® or Probiokid^® (non-commercial name) in 6 international and Chinese databases identified 28 studies, which were classified by indications. Twelve studies show that the probiotic significantly increases the efficacy of standard diarrhea treatment regardless of etiology, reducing the risk of unresolved diarrhea (RR 0.31 [0.23; 0.42]; p < 0.0001) by 69%. In eight studies, the probiotic enhanced immune defenses, assessed by levels of various immune competence and mucosal immunity markers (six studies), and reduced the incidence of common infections (two studies). The probiotic improved iron deficiency anemia treatment efficacy (three studies), reducing the risk of unresolved anemia by 49% (RR 0.51 [0.28; 0.92]; p = 0.0263) and significantly reducing treatment side effects by 47% (RR 0.53 [0.37; 0.77]; p = 0.0009). Other studies support further investigation into this probiotic for oral candidiasis, eczema, feeding intolerance in premature babies, or hyperbilirubinemia in newborns.

Annie Tremblay, Jeremie Auger, Zainab Alyousif, Sara E Caballero Calero, Olivier Mathieu, Daniela Rivero-Mendoza, Amal Elmaoui, Wendy J Dahl, and Thomas A Tompkins. J Neurogastroenterol Motil 2023;29:218-28. https://doi.org/10.5056/jnm22031

Helicobacter pylori (H. pylori) is a bacterial pathogen that infects half of the world population. While standard treatment was initially effective, eradication rates have declined over the last 20 to 30 years, and the use of adjuvants, such as probiotic supplements, has been suggested to improve efficacy. This review presents evidence supporting the use of Lacidofil^®, an established blend of two thoroughly characterized probiotic strains, as an adjuvant to standard therapy for H. pylori eradication. The microbiology and epidemiology of H. pylori infection as well as current approaches to diagnosis and treatment are summarized, and the roles of probiotics to support standard H. pylori treatment are outlined. Lacidofil^® and its component strains are described, and evidence from eight clinical trials supporting its efficacy is presented. H. pylori eradication rates were increased in participants receiving Lacidofil^® (90–100%) compared to controls (70–86.7%), and the incidence of side effects was decreased (e.g., antibiotic-associated diarrhea—Lacidofil^®: 0–13.6%; controls: 20–40.9%). Published summaries, including systematic reviews with meta-analysis and an umbrella review, are discussed. To expand on the discussion of clinical studies, in vivo and in vitro studies are reviewed, including studies using state-of-the-art molecular methods. They characterize Lacidofil^®’s mechanism of action and further support its efficacy as an adjuvant strategy for H. pylori eradication, side effect reduction, and return to gut microbiota homeostasis.

The influence of microbiota dysbiosis in early life is increasingly recognized as a risk factor for the development of several chronic diseases later in life, including an increased risk of asthma, eczema, allergies, obesity, and neurodevelopmental disorders. The question whether the potential lifelong consequences of early life dysbiosis could be mitigated by restoring microbiota composition remains unresolved. However, the current evidence base suggests that protecting the normal development of the microbiome during this critical developmental window could represent a valuable public health strategy to curb the incidence of chronic and lifestyle-related diseases. Probiotic Bifidobacteria are likely candidates for this purpose in newborns and infants considering the natural dominance of this genus on microbiota composition in early life. Moreover, the most frequently reported microbiota composition alteration in association with newborn and infant diseases, including necrotizing enterocolitis and diarrhea, is a reduction in Bifidobacteria levels. Several studies have assessed the effects of B. animalis subsp. lactis strains in newborns and infants, but recent expert opinions recommend analyzing their efficacy at the strain-specific level. Hence, using the B94 strain as an example, this review summarizes the clinical evidence available in infants and children in various indications, discussing the safety and potential modes of actions while providing perspectives on the concept of “non-infant-type” probiotics for infants’ health.

Numerous clinical studies published in the Chinese language support the use of Medilac-S (Bacillus subtilis R0179 and Enterococcus faecium R0026; non-commercial name IBacilluS+) as an adjuvant in various indications, including ulcerative colitis, irritable bowel syndrome, acute gastritis, and Helicobacter pylori therapy. This systematic review with a meta-analysis was conducted to summarize clinical studies evaluating the efficacy of this probiotic formulation as an adjuvant to conventional IBS medications. The systematic literature searches in six international and Chinese databases identified 37 eligible studies, of which 33 reported the efficacy of Medilac-S adjunctive therapy using a standardized categorical scale. These 33 studies were included in the meta-analysis using a random-effect model with a stratification by IBS subtype. Overall, Medilac-S significantly improved the efficacy of conventional IBS treatment (RR = 1.21; 95% CI: 1.17–1.25; and p < 0.0001) with an average probability of treatment effectiveness being 21% higher with the probiotic adjuvant, regardless of the subtype. Adverse events, reported in 78% of the trials, were described as mild-to-moderate and self-resolving, with a similar incidence in the probiotic adjuvant (6.2%; n = 1347) and control (5.9%; n = 1331) groups. The results of this meta-analysis strengthen the conclusions that Medilac-S is a safe and effective adjuvant to a variety of conventional treatments in IBS patients.