Listeria monocytogenes Establishes Commensalism in Germ-Free Mice Through the Reversible Downregulation of Virulence Gene Expression

Antitumor effects of fecal microbiota transplantation: Implications for microbiome modulation in cancer treatment

Fecal microbiome transplantation (FMT) from healthy donors is one of the techniques for restoration of the dysbiotic gut, which is increasingly being used to treat various diseases. Notably, mounting evidence in recent years revealed that FMT has made a breakthrough in the oncology treatment area, especially by improving immunotherapy efficacy to achieve antitumor effects. However, the mechanism of FMT in enhancing antitumor effects of immune checkpoint blockers (ICBs) has not yet been fully elucidated. This review systematically summarizes the role of microbes and their metabolites in the regulation of tumor immunity. We highlight the mechanism of action of FMT in the treatment of refractory tumors as well as in improving the efficacy of immunotherapy. Furthermore, we summarize ongoing clinical trials combining FMT with immunotherapy and further focus on refined protocols for the practice of FMT in cancer treatment, which could guide future directions and priorities of FMT scientific development.

Metagenome Analysis of the Bacterial Characteristics in Invasive Klebsiella Pneumoniae Liver Abscesses

Background

Klebsiella pneumoniae liver abscess (KPLA) combined with extrahepatic migratory infection (EMI) is defined as invasive KPLA (IKPLA) and is associated with a poor prognosis. The mechanism of IKPLA formation is yet to be elucidated. In this study, metagenomic sequencing was used to compare the bacterial characteristics between IKPLA and KPLA to explore the underlying mechanism of invasiveness.

Methods

Clinical details, imaging, and microbial features were retrospectively evaluated by medical record review. Metagenomic sequencing was performed on the pus samples of liver abscesses whose culture results were indicative of monomicrobial Klebsiella pneumoniae (K. pneumoniae). Bacterial diversity and composition in IKPLA and KPLA were comparatively analyzed, and the key pathways and genes that may affect invasiveness were further explored.

Results

Sixteen patients were included in this study. Five patients with EMI were included in the IKPLA group, and the other eleven patients without EMI were assigned to the KPLA group. There was no statistical difference in the hypermucoviscous phenotype and serotype of K. pneumoniae between the two groups. The bacterial diversity of IKPLA was lower than that of KPLA. The abundant taxa in the IKPLA group were primarily species of unclassified Enterobacteriaceae and K. pneumoniae. The KPLA group had a high abundance of the genera Tetrasphaera and Leuconostoc. Metabolic pathway genes represented most of the enriched genes in IKPLA. Fourteen pathogenic genes with significant differences in abundance were identified between the two groups, including ybtS, fepC, phoQ, acrB, fimK, magA, entC, arnT, iucA, fepG, oqxB, entA, tonB, and entF (p < 0.001).

Conclusion

The diversity and bacterial composition of IKPLA were significantly different from those of KPLA. Microbiological changes in the abscess, activation of the related metabolic pathways, and the pathogenic gene expression may constitute a novel mechanism that regulates the invasiveness of KPLA.

Oral administration of Faecalibacterium prausnitzii and Akkermansia muciniphila strains from humans improves atopic dermatitis symptoms in DNCB induced NC/Nga mice

Atopic dermatitis (AD) is a common inflammatory skin disease, and its pathogenesis is closely associated with microbial homeostasis in the gut, namely the gut-skin axis. Particularly, recent metagenomics studies revealed that the abundance of two major bacterial species in the gut, Faecalibacterium prausnitzii and Akkermansia muciniphila, may play a critical role in the pathogenesis of AD, but the effect of these species in AD has not yet been elucidated. To evaluate the potential beneficial effect of F. prausnitzii or A. muciniphila in AD, we conducted an animal model study where F. prausnitzii EB-FPDK11 or A. muciniphila EB-AMDK19, isolated from humans, was orally administered to 2,5-dinitrochlorobenzene (DNCB)-induced AD models using NC/Nga mice at a daily dose of 10⁸ CFUs/mouse for six weeks. As a result, the administration of each strain of F. prausnitzii and A. muciniphila improved AD-related markers, such as dermatitis score, scratching behavior, and serum immunoglobulin E level. Also, the F. prausnitzii and A. muciniphila treatments decreased the level of thymic stromal lymphopoietin (TSLP), triggering the production of T helper (Th) 2 cytokines, and improved the imbalance between the Th1 and Th2 immune responses induced by DNCB. Meanwhile, the oral administration of the bacteria enhanced the production of filaggrin in the skin and ZO-1 in the gut barrier, leading to the recovery of functions. Taken together, our findings suggest that F. prausnitzii EB-FPDK11 and A. muciniphila EB-AMDK19 have a therapeutic potential in AD, which should be verified in humans.