Samantha L. Dawson

The emerging understanding of gut microbiota as 'metabolic machinery' influencing many aspects of physiology has gained substantial attention in the field of psychiatry. This is largely due to the many overlapping pathophysiological mechanisms associated with both the potential functionality of the gut microbiota and the biological mechanisms thought to be underpinning mental disorders. In this systematic review, we synthesised the current literature investigating differences in gut microbiota composition in people with the major psychiatric disorders, major depressive disorder (MDD), bipolar disorder (BD) and schizophrenia (SZ), compared to 'healthy' controls. We also explored gut microbiota composition across disorders in an attempt to elucidate potential commonalities in the microbial signatures associated with these mental disorders. Following the PRISMA guidelines, databases were searched from inception through to December 2021. We identified 44 studies (including a total of 2510 psychiatric cases and 2407 controls) that met inclusion criteria, of which 24 investigated gut microbiota composition in MDD, seven investigated gut microbiota composition in BD, and 15 investigated gut microbiota composition in SZ. Our syntheses provide no strong evidence for a difference in the number or distribution (α-diversity) of bacteria in those with a mental disorder compared to controls. However, studies were relatively consistent in reporting differences in overall community composition (β-diversity) in people with and without mental disorders. Our syntheses also identified specific bacterial taxa commonly associated with mental disorders, including lower levels of bacterial genera that produce short-chain fatty acids (e.g. butyrate), higher levels of lactic acid-producing bacteria, and higher levels of bacteria associated with glutamate and GABA metabolism. We also observed substantial heterogeneity across studies with regards to methodologies and reporting. Further prospective and experimental research using new tools and robust guidelines hold promise for improving our understanding of the role of the gut microbiota in mental and brain health and the development of interventions based on modification of gut microbiota.

Percutaneous needle aspiration of hydatid cysts has long been discouraged because of potential complications, such as anaphylactic shock and the spread of daughter cysts. We used this procedure with successful results, however, in the treatment of a woman with a recurrent hepatic hydatid cyst. The cyst was drained percutaneously using radiologic imaging guidance and then lavaged through a catheter using silver nitrate and hypertonic saline solutions. One year after drainage, all liver function test results remain normal. Although surgical drainage is normally the treatment of choice for hepatic Echinococcus disease, percutaneous catheter drainage may be an alternative therapy for patients who cannot undergo surgery.

Mental disorders including depression and anxiety are often comorbid with gut problems, suggesting a bidirectional relationship between mental health and gut function. Several mechanisms might explain this comorbidity, such as inflammation and immune activation; intestinal permeability; perturbations in the hypothalamic-pituitary-adrenal axis; neurotransmitter/neuropeptide dysregulation; dietary deficiencies; and disturbed gut microbiome composition. The potential of modulating the microbiome-gut-brain axis, and subsequently mental health, through the use of functional foods, is an emerging and novel topic of interest. Fermented foods are considered functional foods due to their putative health benefits. The process of microbial fermentation converts food substrates into more nutritionally and functionally rich products, resulting in functional microorganisms (probiotics), substrates that enhance proliferation of beneficial bacteria in the gut (prebiotics), and bioactive components (biogenics). These functional ingredients act biologically in the gastrointestinal tract and have the ability to modify the gut microbiota, influence translocation of endotoxins and subsequent immune activation, and promote host nutrition. This narrative review explores the theoretical potential of the functional components present in fermented foods to alter gut physiology and to impact the biological mechanisms thought to underpin depression and anxiety. Pre-clinical studies indicate the benefits of fermented foods in relieving perturbed gut function and for animal models of depression and anxiety. However, in humans, the literature relating to the relevance of fermented food for treating or preventing depression and anxiety is sparse, heterogeneous and has significant limitations. This review identifies a critical research gap for further evaluation of fermented foods in the management of depression anxiety in humans.

, a pathogenic strain. Whey and casein isolates and the quantity of dairy consumed did not prompt changes to the gut microbiota composition. All but one study reported no changes to bacterial diversity in response to dairy interventions and one study reported reduction in bacterial diversity in response to milk intake.In conclusion, the results of this review suggest that dairy products such as milk, yogurt, and kefir may modulate the gut microbiota composition in favor to the host. However, the broader health implications of these findings remain unclear and warrant further studies.

In mice, the maternal microbiome influences fetal immune development and postnatal allergic outcomes. Westernized populations have high rates of allergic disease and low rates of gastrointestinal carriage of Prevotella, a commensal bacterial genus that produces short chain fatty acids and endotoxins, each of which may promote the development of fetal immune tolerance. In this study, we use a prebirth cohort (n = 1064 mothers) to conduct a nested case-cohort study comparing 58 mothers of babies with clinically proven food IgE mediated food allergy with 258 randomly selected mothers. Analysis of the V4 region of the 16S rRNA gene in fecal samples shows maternal carriage of Prevotella copri during pregnancy strongly predicts the absence of food allergy in the offspring. This association was confirmed using targeted qPCR and was independent of infant carriage of P. copri. Larger household size, which is a well-established protective factor for allergic disease, strongly predicts maternal carriage of P. copri.