The objective of this narrative review was to check the influence of the human microbiota in the pathogenesis of acne and how the treatment with probiotics as adjuvant or alternative therapy affects the evolution of acne vulgaris. Acne is a chronic inflammatory skin disease involving the pilosebaceous units. The pathogenesis of acne is complex and multifactorial involving genetic, metabolic, and hormonal factors in which both skin and gut microbiota are implicated. Numerous studies have shown the bidirectionality between the intestinal microbiota and skin homeostasis, a communication mainly established by modifying the immune system. Increased data on the mechanisms of action regarding the relevance of Cutibacterium acnes, as well as the importance of the gut–skin axis, are becoming known. Diverse and varied in vitro studies have shown the potential beneficial effects of probiotics in this context. Clinical trials with both topical and oral probiotics are scarce, although they have shown positive results, especially with oral probiotics through the modulation of the intestinal microbiota, generating an anti-inflammatory response and restoring intestinal integrity, or through metabolic pathways involving insulin-like growth factor I (IGF-1). Given the aggressiveness of some standard acne treatments, probiotics should continue to be investigated as an alternative or adjuvant therapy.

Alopecia areata is a multifactorial autoimmune-based disease with a complex pathogenesis. As in all autoimmune diseases, genetic predisposition is key. The collapse of the immune privilege of the hair follicle leading to scalp loss is a major pathogenic event in alopecia areata. The microbiota considered a bacterial ecosystem located in a specific area of the human body could somehow influence the pathogenesis of alopecia areata, as it occurs in other autoimmune diseases. Moreover, the Next Generation Sequencing of the 16S rRNA bacterial gene and the metagenomic methodology have provided an excellent characterization of the microbiota. The aim of this narrative review is to examine the published literature on the cutaneous and intestinal microbiota in alopecia areata to be able to establish a pathogenic link. In this review, we summarize the influence of the microbiota on the development of alopecia areata. We first introduce the general pathogenic mechanisms that cause alopecia areata to understand the influence that the microbiota may exert and then we summarize the studies that have been carried out on what type of gut and skin microbiota is found in patients with this disease.

During the last years, numerous studies have described the presence of significant gut and skin dysbiosis in some dermatological diseases such as atopic dermatitis, psoriasis and acne, among others. How the skin and the gut microbiome play a role in those skin conditions is something to explore, which will shed light on understanding the origin and implication of the microbiota in their pathophysiology. Several studies provide evidence for the influence of probiotic treatments that target the modulation of the skin and intestinal microbiota in those disorders and a positive influence of orally administered probiotics on the course of these dermatosis. The pathologies in which the therapeutic role of the probiotic has been explored are mainly atopic dermatitis, psoriasis and acne. This article aims to review these three dermatological diseases, their relationship with the human microbiota and specially the effect of probiotics usage. In addition, the pathophysiology in each of them and the hypotheses about possible mechanisms of the action of probiotics will be described.

Background: The influence of the microbiome on neurological diseases has been studied for years. Recent findings have shown a different composition of gut microbiota detected in patients with multiple sclerosis (MS). The role of this dysbiosis is still unknown. Objective: We analyzed the gut microbiota of 15 patients with active relapsing-remitting multiple sclerosis (RRMS), comparing with diet-matched healthy controls. Method: To determine the composition of the gut microbiota, we performed high-throughput sequencing of the 16S ribosomal RNA gene. The specific amplified sequences were in the V3 and V4 regions of the 16S ribosomal RNA gene. Results: The gut microbiota of RRMS patients differed from healthy controls in the levels of the Lachnospiraceae, Ezakiella, Ruminococcaceae, Hungatella, Roseburia, Clostridium, Shuttleworthia, Poephyromonas, and Bilophila genera. All these genera were included in a logistic regression analysis to determine the sensitivity and the specificity of the test. Finally, the ROC (receiver operating characteristic) and AUC with a 95% CI were calculated and best-matched for Ezakiella (AUC of 75.0 and CI from 60.6 to 89.4) and Bilophila (AUC of 70.2 and CI from 50.1 to 90.4). Conclusions: There is a dysbiosis in the gut microbiota of RRMS patients. An analysis of the components of the microbiota suggests the role of some genera as a predictive factor of RRMS prognosis and diagnosis.

(1) Background: Given the autoimmune nature of Alopecia Areata (AA) and the immunomodulatory properties of probiotics, this trial was conducted to evaluate the efficacy of a probiotic mixture, consisting of Lactobacillus rhamnosus and Bifidobacterium longum strains, as an adjuvant treatment in a group of AA patients. (2) Method: This study was a 24-week, randomized, double-blind, placebo-controlled clinical trial. Twenty-six patients with AA were included in this study, and their clinical progression, along with changes in gut and skin microbiota, were analyzed. (3) Results: A higher proportion of AA patients treated with the probiotic formula showed improvement compared to the placebo group, based on both the reduction in the number of AA plaques (56% vs. 30%) and the affected scalp surface area (45% vs. 20%). For “activity”, “inactivity”, and “regrowth”, an improvement in 55%, 67%, and 55% of patients was, respectively, observed in the probiotic group, compared to 50%, 40%, and 30% in the placebo group. No changes were observed in the gut microbiota during the intervention period. Regarding skin microbiota, changes were detected in the probiotic group, with reductions in characteristic genera during the study. (4) Conclusions: To our knowledge, this is the first clinical trial assessing the efficacy of a probiotic product in patients with AA. This probiotic mixture in a routine clinical practice setting appears to improve the course of patients. In addition, the skin microbiota of scalp lesions was modified using the probiotic treatment.

Bladder cancer is around the 10th most diagnosed cancer, although has a considerable mortality. Recent research and new methodologies have discarded the historical dogma that the bladder (and urine) was sterile under normal conditions. Specifically, only a few studies have reported a detailed analysis of the urinary microbiota in patients with bladder cancer, thus exhibiting a remarkable variability due to the low biomass of the urinary microbiota and the influence of many factors. Nevertheless, this research shows us signals that urinary microbiota is a factor to be considered in the pathophysiology of bladder cancer. More importantly, probiotics could be useful as an adjuvant therapy to reduce the recurrence rate or increase the disease-free period after surgery. In vitro studies and animal assays have shown promising results, but the research in this context has also been scarce, and only a few studies have been conducted in humans. In summary, there is little evidence of the possible beneficial effect of probiotics in controlling the overgrowth of genera that could be involved in the carcinogenesis of bladder cancer. This narrative review aims to compile all the evidence to date on the therapeutic potential of probiotics injected directly into the bladder or orally administered.