Christensenella minuta mitigates behavioral and cardiometabolic hallmarks of social defeat stress.

Psychological stress during early development and adolescence may increase the risk of psychiatric and cardiometabolic comorbidities in adulthood. The gut microbiota has been associated with mental health problems such as depression and anxiety and with cardiometabolic disease, but the potential role of the gut microbiota in their comorbidity is not well understood. We investigated the effects and mode of action of the intestinal bacterium Christensenella minuta DSM 32891 on stress-induced mental health and cardiometabolic disturbances in a mouse model of social defeat stress. We demonstrate that administered C. minuta alleviates chronic stress-induced depressive, anxiogenic and antisocial behavior. These effects are attributed to the bacterium's ability to modulate the hypothalamic-pituitary-adrenal axis, which mediates the stress response. This included the oversecretion of corticosterone and the overexpression of its receptors, as well as the metabolism of dopamine (DA) and the expression of its receptors (D1, D2L and D2S). Additionally, C. minuta administration reduced chronically induced inflammation in plasma, spleen and some brain areas, which likely contribute to the recovery of physical and behavioral function. Furthermore, C. minuta administration prevented chronic stress-induced cardiovascular damage by regulating key enzymes mediating liver fibrosis and oxidative stress. Finally, C. minuta increased the abundance of bacteria associated with mental health. Overall, our study highlights the potential of microbiota-directed interventions to alleviate both the physical and mental effects of chronic stress.

Gut microbiome and anti-viral immunity in COVID-19.

SARS-CoV-2 mainly affects the respiratory system, but the gastrointestinal tract is also a target. Prolonged gut disorders, in COVID-19 patients, were correlated with decreased richness and diversity of the gut microbiota, immune deregulation and delayed viral clearance. Although there are no definitive conclusions, ample evidence would suggest that the gut microbiome composition and function play a role in COVID-19 progression. Microbiome modulation strategies for population stratification and management of COVID-19 infection are under investigation, representing an area of interest in the ongoing pandemic. In this review, we present the existing data related to the interaction between gut microbes and the host's immune response to SARS-CoV-2 and discuss the implications for current disease management and readiness to face future pandemics.

Is there a widespread clone of Serratia marcescens producing outbreaks worldwide?

BACKGROUND: Serratia marcescens frequently causes outbreaks in healthcare settings. There are few studies using high-throughput sequencing (HTS) that analyse S. marcescens outbreaks. We present the analysis of two outbreaks in neonatal intensive care units (NICUs) in hospitals from the Comunitat Valenciana (CV, Spain) and the impact of using different reference genomes. METHODS: DNA from cultured isolates was extracted and sequenced by HTS using Illumina NextSeq. Reads were mapped against two reference genomes, strains UMH9 and Db11, and the unmapped fraction of the genomes was assembled to fully genetically characterize the isolates. FINDINGS: Isolates from the first outbreak were identical to the UMH9 reference, an unrelated isolate obtained three years earlier in the USA. This did not occur when the Db11 strain, a standard reference for S. marcescens, was used as the reference for mapping. To check whether UMH9 was a widely distributed clone spreading in the CV, the second outbreak isolates were mapped against this reference. They were not closely related to this strain, and this outbreak could be defined as such regardless of the reference used for mapping the reads. CONCLUSIONS: The choice of the reference for genomic analysis of outbreaks is a critical decision. In the case of the first outbreak, this choice changed the interpretation of the results drastically, allowing or preventing the definition of the outbreak according to the reference used. Although HTS is a powerful tool for epidemiological analysis, it is still essential to collect microbiological and epidemiological data for the correct interpretation of the results.