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.

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.