Background There is mounting evidence that SARS-CoV-2 targets tissues beyond the respiratory tract. Long-term sequelae after COVID-19 are frequent and of major concern. Prolonged virus detection in the gut has been particularly intriguing. Of note, SARS-CoV-2 infection also disturbs the gut microbiota composition, a finding linked with disease severity in patients with COVID-19. Here, we aimed to characterize the functional role of the gut microbiota in the long-term consequences of COVID-19. To this end, we characterized the gut microbiota from COVID-19 human subjects and followed the effects of human fecal transfer to germ-free mice. Results The gut microbiota of post-COVID subjects (up to 4 months from the initial positive test) revealed a remarkable predominance of Enterobacteriaceae strains with multidrug-resistance phenotype compared to healthy controls. After fecal transfer to germ-free mice, animals receiving samples from post-COVID subjects displayed higher lung inflammation and increased susceptibility to pulmonary infection caused by an antimicrobial resistant Klebsiella pneumoniae strain. These mice also showed poorer cognitive performance associated with increased expression of TNF-α, reduced levels of brain-derived neurotrophic factor-BDNF and postsynaptic density protein-PSD-95 in the brain, as well as alterations of several biochemical pathways. These alterations were observed in the absence of SARS-CoV-2, suggesting that alterations in the gut microbiota caused them. Consistent with this hypothesis, brain dysfunctions induced in a mouse model of coronavirus infection were partially prevented by modulation of the microbiota via treatment with the commensal probiotic bacteria Bifidobacterium longum 51A. Conclusions Our results show prolonged impact of SARS-CoV-2 infection in the gut microbiota that persists even after the individuals have cleared the virus. Increased Enterobacteriaceae with antimicrobial resistance phenotype were of particular concern. Moreover, microbiota transfer from post-COVID subjects induced loss of brain cognitive functions and impaired lung defense in mice. Altogether, our work emphasizes the importance of microbiota as a target for therapies to help treat post-COVID sequelae.
Corynebacterium striatum, a common constituent of the human skin microbiome, is now considered an emerging multidrug-resistant pathogen of immunocompromised and chronically ill patients. However, little is known about the molecular mechanisms in the transition from colonization to the multidrugresistant (MDR) invasive phenotype in clinical isolates. This study performed a comprehensive pangenomic analysis of C. striatum, including isolates from 'normal skin microbiome' and from MDR infections, to gain insights into genetic factors contributing to pathogenicity and multidrug resistance in this species. For this, three novel genome sequences were obtained from clinical isolates of C. striatum of patients from Brazil, and other 24 complete or draft C. striatum genomes were retrieved from GenBank, including the ATCC6940 isolate from the Human Microbiome Project. Analysis of C. striatum strains demonstrated the presence of an open pan-genome (α = 0.852803) containing 3,816 gene families, including 15 antimicrobial resistance (AMR) genes and 32 putative virulence factors. The core and accessory genomes included 1,297 and 1,307 genes, respectively. The identi ed AMR genes are primarily associated with resistance to aminoglycosides and tetracyclines. Of these, 66.6% are present in genomic islands, and four AMR genes, including aac(6')-ib7, are located in a class 1-integron. In conclusion, our data indicated that C. striatum possesses genomic characteristics favorable to the invasive phenotype, with high genomic plasticity, a robust genetic arsenal for iron acquisition, and important virulence determinants and AMR genes present in mobile genetic elements.
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