The Gut Bacterial Community Potentiates Clostridioides difficile Infection Severity

Effect of Dietary Concentrate-to-Forage Ratios During the Cold Season on Slaughter Performance, Meat Quality, Rumen Fermentation and Gut Microbiota of Tibetan Sheep

This study aimed to investigate the effects of different dietary concentrate-to-forage ratios on slaughter performance, meat quality, rumen fermentation, rumen microbiota and fecal microbiota in Tibetan sheep. A total of sixty male Tibetan sheep were equally allocated into three dietary groups based on concentrate-to-forage ratios, i.e., 30:70 (C30), 50:50 (C50), and 70:30 (C70). Compared with the C30 group, sheep fed the C70 diet resulted in a higher (p < 0.05) slaughter live weight (SLW), hot carcass weight (HCW), dressing percentage (DP), eye muscle area, average daily gain (ADG), and ruminal total volatile fatty acids concentration and propionate molar proportion and lower (p < 0.05) shear force and cooking loss of meat, and ruminal acetate molar proportion and acetate:propionate ratio. Sheep in the C50 group exhibited a higher (p < 0.05) SLW, HCW, ADG, and ruminal propionate molar proportion and lower (p < 0.05) shear force and cooking loss of meat, and ruminal acetate molar proportion and acetate: propionate ratio compared with the C30 group. In rumen fluid, the relative abundance of Butyrivibrio was lower (p = 0.031) in the C30 group, and that of Ruminococcus was higher (p = 0.003) in the C70 group compared with the C50 group. In feces, genus Monoglobus and UCG_002 were the most abundant in the C30 group (p < 0.05), and the relative abundance of Prevotella was significantly higher in the C70 group than in other groups (p = 0.013). Correlation analysis revealed possible links between slaughter performance and meat quality and altered microbiota composition in the rumen and feces of Tibetan sheep. Overall, feeding a C70 diet resulted in superior carcass characteristics and meat quality in Tibetan sheep, thus laying a theoretical basis for the application of short-term remote feeding during the cold season.

Alleviating D-Galactose-Induced Aging in Mice by Modulating Gut-Liver Axis Using Lactiplantibacillus plantarum TY-Y10

Oxidative stress is closely linked to aging. Probiotics, whether viable or heat-inactivated, have shown antioxidant properties; however, their effect and mechanism of action in reducing oxidative stress during aging remains underexplored. This study examined the effects of viable and heat-inactivated Lactiplantibacillus plantarum TY-Y10 (L. plantarum TY-Y10) on D-galactose (D-gal)-induced aging in mice, aiming to uncover potential anti-aging mechanisms. Mice were induced to age with D-gal injections, then treated with sodium ascorbate (positive control) or varying doses of L. plantarum TY-Y10 for eight weeks. After treatment, oxidative stress markers, gut microbiota, and liver health were analyzed. Results showed that L. plantarum TY-Y10 decreased malondialdehyde (MDA) and inflammatory markers while increasing antioxidant levels (glutathione, superoxide dismutase, catalase and glutathione peroxidase). Liver damage was reduced, and expression of Nrf2 and related antioxidant enzymes improved. Additionally, L. plantarum TY-Y10 enhanced the abundance of short-chain fatty acid-producing bacteria, boosting fecal short-chain fatty acid levels. In short, both viable and heat-inactivated L. plantarum TY-Y10 mitigated oxidative stress in aging mice by modulating gut microbiota and activating liver antioxidant pathways through the gut-liver axis.

Evidences and perspectives on the association between gut microbiota and sepsis: A bibliometric analysis from 2003 to 2023

Background

In the last two decades, the role of the gut microbiome in the development, maintenance, and outcome of sepsis has received increased attention; however, few descriptive studies exist on its research focus, priorities, and future prospects. This study aimed to identify the current state, evolution, and emerging trends in the field of gut microbiota and sepsis using bibliometric analysis.

Methods

All publications on sepsis and gut microbiota were retrieved from the Web of Science Core Collection and included in this study. VOSviewer, CiteSpace, and the Web of Science online analysis platform were used to visualize trends based on publication country, institution, author, journal, and keywords.

Results

A total of 1,882 articles on sepsis-related gut microbiota were screened, mainly from 95 countries or regions and 2,581 institutions. The United States and China contributed the most to this research field, with 521 (27.683 %) and 376 (19.979 %) articles, respectively. Scientists from the University of California were the most prolific, publishing 63 (3.348 %) articles. Cani PD published papers with the highest H-index, establishing himself as a leader in the field. The most publications were published in the journals "Nutrients" and "PLOS One." The journals with the most co-citations were "PLOS One," "Nature," and "Gut." The most used keywords were prebiotics, gut microbiota, and sepsis. The keyword burst research analysis revealed that research on treatment strategies based on the intestinal microbiota, intestine-liver axis, and regulatory mechanisms of bacterial metabolites are currently hot directions.

Conclusion

This study presents a global overview of the current state and potential trends in the field of sepsis-related gut microbiota. This study identified hot research sub-directions and new trends through comparison and analysis, which will aid in the development of this field.

Microbiome and infectious disease: diagnostics to therapeutics

Over 300 years of research on the microbial world has revealed their importance in human health and disease. This review explores the impact and potential of microbial-based detection methods and therapeutic interventions, integrating research of early microbiologists, current findings, and future perspectives.

Clostridioides difficile and Gut Microbiota: From Colonization to Infection and Treatment

Clostridioides difficile is the main causative agent of antibiotic-associated diarrhea (AAD) in hospitals in the developed world. Both infected patients and asymptomatic colonized individuals represent important transmission sources of C. difficile. C. difficile infection (CDI) shows a large range of symptoms, from mild diarrhea to severe manifestations such as pseudomembranous colitis. Epidemiological changes in CDIs have been observed in the last two decades, with the emergence of highly virulent types and more numerous and severe CDI cases in the community. C. difficile interacts with the gut microbiota throughout its entire life cycle, and the C. difficile's role as colonizer or invader largely depends on alterations in the gut microbiota, which C. difficile itself can promote and maintain. The restoration of the gut microbiota to a healthy state is considered potentially effective for the prevention and treatment of CDI. Besides a fecal microbiota transplantation (FMT), many other approaches to re-establishing intestinal eubiosis are currently under investigation. This review aims to explore current data on C. difficile and gut microbiota changes in colonized individuals and infected patients with a consideration of the recent emergence of highly virulent C. difficile types, with an overview of the microbial interventions used to restore the human gut microbiota.

Commensal-pathogen dynamics structure disease outcomes during Clostridioides difficile colonization

Gastrointestinal colonization by Clostridioides difficile is common in healthcare settings and ranges in clinical presentation from asymptomatic carriage to lethal C. difficile infection (CDI). We used a systems biology approach to investigate why patients colonized with C. difficile have a range of outcomes. Microbiota-humanization of germ-free mice with fecal samples from toxigenic C. difficile carriers revealed a spectrum of virulence among clade 1 lineages and identified commensal Blautia associated with markers of non-pathogenic colonization. Using gnotobiotic mice engrafted with defined human microbiota, we observed strain-specific CDI severity across clade 1 strains. Yet, mice engrafted with a higher diversity community were protected from severe disease across all strains without suppression of C. difficile colonization. These results indicate that when colonization resistance has been breached without overt infection, commensals can attenuate a diversity of virulent strains without inhibiting pathogen colonization, providing insight into determinants of stable C. difficile carriage.

Reviewing the Clostridioides difficile Mouse Model: Insights into Infection Mechanisms

Clostridioides difficile is an anaerobic, spore-forming bacterium associated with intestinal infection, manifesting a broad spectrum of gastrointestinal symptoms, ranging from mild diarrhea to severe colitis. A primary risk factor for the development of C. difficile infection (CDI) is antibiotic exposure. Elderly and immunocompromised individuals are particularly vulnerable to CDI. A pivotal aspect for comprehending the complexities of this infection relies on the utilization of experimental models that mimic human CDI transmission, pathogenesis, and progression. These models offer invaluable insights into host-pathogen interactions and disease dynamics, and serve as essential tools for testing potential therapeutic approaches. In this review, we examine the animal model for CDI and delineate the stages of infection, with a specific focus on mice. Our objective is to offer an updated description of experimental models employed in the study of CDI, emphasizing both their strengths and limitations.

Gut Microbiota-Gut Metabolites and Clostridioides difficile Infection: Approaching Sustainable Solutions for Therapy

Clostridioides difficile (C. difficile) infection (CDI) is the most common hospital-acquired infection. With the combination of a high rate of antibiotic resistance and recurrence, it has proven to be a debilitating public health threat. Current treatments for CDI include antibiotics and fecal microbiota transplantation, which contribute to recurrent CDIs and potential risks. Therefore, there is an ongoing need to develop new preventative treatment strategies for CDI. Notably, gut microbiota dysbiosis is the primary risk factor for CDI and provides a promising target for developing novel CDI therapy approaches. Along with gut microbiota dysbiosis, a reduction in important gut metabolites like secondary bile acids and short-chain fatty acids (SCFAs) were also seen in patients suffering from CDI. In this review study, we investigated the roles and mechanisms of gut microbiota and gut microbiota-derived gut metabolites, especially secondary bile acids and SCFAs in CDI pathogenesis. Moreover, specific signatures of gut microbiota and gut metabolites, as well as different factors that can modulate the gut microbiota, were also discussed, indicating that gut microbiota modulators like probiotics and prebiotics can be a potential therapeutic strategy for CDI as they can help restore gut microbiota and produce gut metabolites necessary for a healthy gut. The understanding of the associations between gut microbiota-gut metabolites and CDI will allow for developing precise and sustainable approaches, distinct from antibiotics and fecal transplant, for mitigating CDI and other gut microbiota dysbiosis-related diseases.

Liberation of host heme by Clostridioides difficile-mediated damage enhances Enterococcus faecalis fitness during infection

IMPORTANCE

Clostridioides difficile and Enterococcus faecalis are two pathogens of great public health importance. Both bacteria colonize the human gastrointestinal tract where they are known to interact in ways that worsen disease outcomes. We show that the damage associated with C. difficile infection (CDI) releases nutrients that benefit E. faecalis. One particular nutrient, heme, allows E. faecalis to use oxygen to generate energy and grow better in the gut. Understanding the mechanisms of these interspecies interactions could inform therapeutic strategies for CDI.

Transplant of microbiota from Crohn's disease patients to germ-free mice results in colitis

Although the role of the intestinal microbiota in the pathogenesis of inflammatory bowel disease (IBD) is beyond debate, attempts to verify the causative role of IBD-associated dysbiosis have been limited to reports of promoting the disease in genetically susceptible mice or in chemically induced colitis. We aimed to further test the host response to fecal microbiome transplantation (FMT) from Crohn's disease patients on mucosal homeostasis in ex-germ-free (xGF) mice. We characterized and transferred fecal microbiota from healthy patients and patients with defined Crohn's ileocolitis (CD_L3) to germ-free mice and analyzed the resulting microbial and mucosal homeostasis by 16S profiling, shotgun metagenomics, histology, immunofluorescence (IF) and RNAseq analysis. We observed a markedly reduced engraftment of CD_L3 microbiome compared to healthy control microbiota. FMT from CD_L3 patients did not lead to ileitis but resulted in colitis with features consistent with CD: a discontinued pattern of colitis, more proximal colonic localization, enlarged isolated lymphoid follicles and/or tertiary lymphoid organ neogenesis, and a transcriptomic pattern consistent with epithelial reprograming and promotion of the Paneth cell-like signature in the proximal colon and immune dysregulation characteristic of CD. The observed inflammatory response was associated with persistently increased abundance of Ruminococcus gnavus, Erysipelatoclostridium ramosum, Faecalimonas umbilicate, Blautia hominis, Clostridium butyricum, and C. paraputrificum and unexpected growth of toxigenic C. difficile, which was below the detection level in the community used for inoculation. Our study provides the first evidence that the transfer of a dysbiotic community from CD patients can lead to spontaneous inflammatory changes in the colon of xGF mice and identifies a signature microbial community capable of promoting colonization of pathogenic and conditionally pathogenic bacteria.

Animal and In Vitro Models as Powerful Tools to Decipher the Effects of Enteric Pathogens on the Human Gut Microbiota

Examining the interplay between intestinal pathogens and the gut microbiota is crucial to fully comprehend the pathogenic role of enteropathogens and their broader impact on human health. Valid alternatives to human studies have been introduced in laboratory practice to evaluate the effects of infectious agents on the gut microbiota, thereby exploring their translational implications in intestinal functionality and overall health. Different animal species are currently used as valuable models for intestinal infections. In addition, considering the recent advances in bioengineering, futuristic in vitro models resembling the intestinal environment are also available for this purpose. In this review, the impact of the main human enteropathogens (i.e., Clostridioides difficile, Campylobacter jejuni, diarrheagenic Escherichia coli, non-typhoidal Salmonella enterica, Shigella flexneri and Shigella sonnei, Vibrio cholerae, and Bacillus cereus) on intestinal microbial communities is summarized, with specific emphasis on results derived from investigations employing animal and in vitro models.

Fungal and bacterial gut microbiota differ between Clostridioides difficile colonization and infection

Aim: The bacterial microbiota is well-recognized for its role in Clostridioides difficile colonization and infection, while fungi and yeasts remain understudied. The aim of this study was to analyze the predictive value of the mycobiota and its interactions with the bacterial microbiota in light of C. difficile colonization and infection. Methods: The mycobiota was profiled by ITS2 sequencing of fecal DNA from C. difficile infection (CDI) patients (n = 29), asymptomatically C. difficile colonization (CDC) patients (n = 38), and hospitalized controls with C. difficile negative stool culture (controls; n = 38). Previously published 16S rRNA gene sequencing data of the same cohort were used additionally for machine learning and fungal-bacterial network analysis. Results: CDI patients were characterized by a significantly higher abundance of Candida spp. (MD 0.270 ± 0.089, P = 0.002) and Candida albicans (MD 0.165 ± 0.082, P = 0.023) compared to controls. Additionally, they were deprived of Aspergillus spp. (MD -0.067 ± 0.026, P = 0.000) and Penicillium spp. (MD -0.118 ± 0.043, P = 0.000) compared to CDC patients. Network analysis revealed a positive association between several fungi and bacteria in CDI and CDC, although the analysis did not reveal a direct association between Clostridioides spp. and fungi. Furthermore, the microbiota machine learning model outperformed the models based on the mycobiota and the joint microbiota-mycobiota model. The microbiota classifier successfully distinguished CDI from CDC [Area Under the Receiver Operating Characteristic (AUROC) = 0.884] and CDI from controls (AUROC = 0.905). Blautia and Bifidobacterium were marker genera associated with CDC patients and controls. Conclusion: The gut mycobiota differs between CDI, CDC, and controls and may affect Clostridioides spp. through indirect interactions. The mycobiota data alone could not successfully discriminate CDC from controls or CDI patients and did not have additional predictive value to the bacterial microbiota data. The identification of bacterial marker genera associated with CDC and controls warrants further investigation.

Strategies for applying probiotics in the antibiotic management of Clostridioides difficile infection

The vital role of probiotics in the food field has been widely recognized, and at the same time, probiotics are gradually exhibiting surprising effects in the field of nutraceuticals, especially in regulating gut inflammation and the nutritional environment. As a dietary supplement in clinical nutrition, the coadministration of probiotics with antibiotics model has been applied to prevent intestinal infections caused by Clostridioides difficile. However, the mechanism behind this "bacteria-drug combination" model remains unclear. In particular, the selection of specific probiotic strains, the order of probiotics or antibiotics, and the time interval of coadministration are key issues that need to be further explored and clarified. Here, we focus on the issues mentioned above and give reasonable opinions, mainly including: (1) probiotics are safer and more effective when they intervene after antibiotics have been used; (2) the choice of the time interval between coadministration should be based on the metabolism of antibiotics in the host, differences in probiotic strains, the baseline ecological environment of the host's intestine, and the host immune level; in addition, the selection of the coadministration regime should also take into account factors such as the antibiotic sensitivity of probiotics and dosage of probiotics; and (3) by encapsulating probiotics, combining probiotics with prebiotics, and developing next-generation probiotics (NGPs) and postbiotic formulations, we can provide a more reasonable reference for this type of "bacteria-drug combination" model, and also provide targeted guidance for the application of probiotic dietary supplements in the antibiotic management of C. difficile infection.

Transcriptome and the gut microbiome analysis of the impacts of Brucella abortus oral infection in BALB/c mice

Brucellosis is a zoonotic infectious disease caused by Brucella spp, which could cause serious economic losses to animal husbandry and threaten human public health. Ingestion of contaminated animal products is a common way to acquire Brucella infection in humans, while research on effect of oral Brucella infection on host gut microbiota and the gene expression in intestinal tissues is limited. In the present study, 16S rRNA sequencing and RNA sequencing were conducted to explore gut microbiota and expression profiles of mRNAs in the colon of BALB/c mice, which were infected by Brucella abortus 2308. The fecal samples were collected at 7 and 28 days post infection to observe changes in the gut microbiota during Brucella infection. In the alpha diversity analysis, significantly increased Chao 1 index was observed at 28 days after Brucella infection. The Bray-Curtis distancebased principal coordinate analysis indicated that the WT group showed a separation from the Brucella infection groups. In addition, analysis of composition of microbes revealed that Prevotellaceae_NK3B31_group were more abundant in 1 week and 4 week infection groups, while Turicibacter was only more abundant in 4 week infection group. Based on the RNA-seq assay, a total of 45 differentially expressed genes were detected between Brucella abortus infection group and control group. Furthermore, KEGG pathway enrichment analysis showed that protein processing in endoplasmic reticulum, Legionellosis, Spliceosome, Hippo signaling pathway and Influenza A were significantly enriched in response to Brucella abortus infection. Our finding will help to improve the knowledge of the mechanisms underlying Brucella infection and may provide novel targets for future treatment of this pathogen infection.

Pre-colonization with the fungus Candida glabrata exacerbates infection by the bacterial pathogen Clostridioides difficile in a murine model

The contributions of commensal fungi to human health and disease are not well understood. Candida species such as C. albicans and C. glabrata are opportunistic pathogenic fungi and common colonizers of the human intestinal tract. They have been shown to affect the host immune system and interact with the gut microbiome and pathogenic microorganisms. Therefore, Candida species could be expected to play important ecological roles in the host gastrointestinal tract. Previously, our group demonstrated that pre-colonization of mice with C. albicans protected them against lethal C. difficile infection (CDI). Here, we show that mice pre-colonized with C. glabrata succumbed to CDI more rapidly than mice that were not pre-colonized suggesting an enhancement in C. difficile pathogenesis. Further, when C. difficile was added to pre-formed C. glabrata biofilms, an increase in matrix and overall biomass was observed. These effects were also shown with C. glabrata clinical isolates. Interestingly, the presence of C. difficile increased C. glabrata biofilm susceptibility to caspofungin, indicating potential effects on the fungal cell wall. Defining this intricate and intimate relationship will lead to an understanding of the role of Candida species in the context of CDI and novel aspects of Candida biology. IMPORTANCE Most microbiome studies have only considered the bacterial populations while ignoring other members of the microbiome such as fungi, other eukaryotic microorganisms, and viruses. Therefore, the role of fungi in human health and disease has been significantly understudied compared to their bacterial counterparts. This has generated a significant gap in knowledge that has negatively impacted disease diagnosis, understanding, and the development of therapeutics. With the development of novel technologies, we now have an understanding of mycobiome composition, but we do not understand the roles of fungi in the host. Here, we present findings showing that Candida glabrata, an opportunistic pathogenic yeast that colonizes the mammalian gastrointestinal tract, can impact the severity and outcome of a Clostridioides difficile infection (CDI) in a murine model. These findings bring attention to fungal colonizers during CDI, a bacterial infection of the gastrointestinal tract.

Clostridioides difficile and Enterococci's Interplay in the Human Gut: Bacterial Alliance or Competition? A Systematic Literature Review

Clostridioides difficile and Enterococcus spp. are two common bacterial pathogens populating the human microbiota. We possess scant data on how Clostridioides difficile interacts with Enterococcus spp. in the gut microbiota in subjects colonized with Clostridioides difficile or during a Clostridioides difficile infection. We carried out a systematic review of studies on Enterococcus spp. and Clostridioides difficile's interaction in the gut microbiota and on the effect of Enterococcus spp. gut colonization on CDI development. Studies on Enterococcus spp. and Clostridioides difficile's interaction in the gut microbiota and on the effect of Enterococcus spp. gut colonization on CDI were searched using the search terms "clostridium", "clostridioides", "difficile" and "enterococcus" on the MEDLINE and SCOPUS databases. PubMed was searched until 1 May 2023. An English language restriction was applied. The risk of bias in the included studies was not assessed. Quantitative and qualitative information was summarized in textual descriptions. Fourteen studies, published from August 2012 to November 2022, on Clostridioides difficile and Enterococcus spp.'s interaction in the gut microbiota met the inclusion criteria. The studies included in our systematic review reported evidence that the Enterococcus spp. intestinal burden represents a risk factor for the occurrence of CDI. There is supporting evidence that Enterococcus spp. play a role in CDI development and clinical outcomes.

Microbial ecology between Clostridioides difficile and gut microbiota

Clostridioides difficile colonizes a polymicrobial environment in the intestine and is a causative agent for antibiotic-associated diarrhea (AAD) and pseudomembranous colitis (PMC). The most important virulence factors of C. difficile are bacterial toxins, and three toxins (toxin A, toxin B, and binary toxin) are produced by toxigenic strains. Other virulence factors include spores, flagella, capsules, biofilms, hydrolytic enzymes and adhesins. C. difficile infection (CDI) is specifically diagnosed by anaerobic culture and toxin detection by either nucleic acid amplification test (NAAT) or enzyme-linked immunosorbent assay (ELISA). For treatment of CDI, metronidazole, vancomycin and fidaxomicin are used based on the severity of CDI. Mutual interaction between C. difficile and gut microbiota is associated with pathogenesis of CDI, and decreased microbial diversity with altered gut microbiome was detected in CDI patients. Restoration of certain gut microbiota is considered to be potentially effective for the prevention and treatment of CDI, and an ideal goal for CDI patients is restoration of the gut microbiota to a healthy state. Fecal microbiota transplantation (FMT) is a highly successful method of microbiome restoration and has been reported to be effective for the prevention of recurrent CDI. In addition, approaches to restoring the gut microbiota by using probioitcs and live biotherapeutic products (LBPs) are currently being studied to examine the effect on CDI. Further microbial ecological research on C. difficile and gut microbiota could lead to a better understanding of the pathogenesis and treatment of CDI.

Clostridioides difficile infection: microbe-microbe interactions and live biotherapeutics

Clostridioides difficile is a gram-positive, spore-forming, obligate anaerobe that infects the colon. C. difficile is estimated to cause nearly half a million cases in the United States annually, with about 29,000 associated deaths. Unfortunately, the current antibiotic treatment is not ideal. While antibiotics can treat the infections, they also disrupt the gut microbiota that mediates colonization resistance against enteric pathogens, including C. difficile; disrupted gut microbiota provides a window of opportunity for recurrent infections. Therefore, therapeutics that restore the gut microbiota and suppress C. difficile are being evaluated for safety and efficacy. This review will start with mechanisms by which gut bacteria affect C. difficile pathogenesis, followed by a discussion on biotherapeutics for recurrent C. difficile infections.

Crosstalk between Gut Microbiota and Host Immunity: Impact on Inflammation and Immunotherapy

Gut microbes and their metabolites are actively involved in the development and regulation of host immunity, which can influence disease susceptibility. Herein, we review the most recent research advancements in the gut microbiota-immune axis. We discuss in detail how the gut microbiota is a tipping point for neonatal immune development as indicated by newly uncovered phenomenon, such as maternal imprinting, in utero intestinal metabolome, and weaning reaction. We describe how the gut microbiota shapes both innate and adaptive immunity with emphasis on the metabolites short-chain fatty acids and secondary bile acids. We also comprehensively delineate how disruption in the microbiota-immune axis results in immune-mediated diseases, such as gastrointestinal infections, inflammatory bowel diseases, cardiometabolic disorders (e.g., cardiovascular diseases, diabetes, and hypertension), autoimmunity (e.g., rheumatoid arthritis), hypersensitivity (e.g., asthma and allergies), psychological disorders (e.g., anxiety), and cancer (e.g., colorectal and hepatic). We further encompass the role of fecal microbiota transplantation, probiotics, prebiotics, and dietary polyphenols in reshaping the gut microbiota and their therapeutic potential. Continuing, we examine how the gut microbiota modulates immune therapies, including immune checkpoint inhibitors, JAK inhibitors, and anti-TNF therapies. We lastly mention the current challenges in metagenomics, germ-free models, and microbiota recapitulation to a achieve fundamental understanding for how gut microbiota regulates immunity. Altogether, this review proposes improving immunotherapy efficacy from the perspective of microbiome-targeted interventions.

Comparison between Symptomatic and Asymptomatic Mice after Clostridioides difficile Infection Reveals Novel Inflammatory Pathways and Contributing Microbiota

Clostridioides difficile causes the highest number of nosocomial infections. Currently, treatment options for C. difficile infection (CDI) are very limited, resulting in poor treatment outcomes and high recurrence rates. Although the disease caused by CDI is inflammatory in nature, the role of inflammation in the development of CDI symptoms is contradictory and not completely understood. Hence, the use of anti-inflammatory medication is debatable in CDI. In the current study, we evaluated the genetic and microbiome profiles of mice after infection with C. difficile. These mice were categorized based on the severity of CDI and the results were viewed accordingly. Our results indicate that certain genes are upregulated in severe CDI more than in the moderate case. These include oncostatin-M (OSM), matrix metalloprotease 8 (MMP8), triggering receptor expressed on myeloid cells 1 (Trem-1), and dual oxidase 2 (Duox2). We also investigated the microbiome composition of CDI mice before and after infecting with C. difficile. The results show that C. difficile abundance is not indicative of diseases severity. Certain bacterial species (e.g., Citrobacter) were enriched while others (e.g., Turicibacter) were absent in severe CDI. This study identifies novel inflammatory pathways and bacterial species with a potential role in determining the severity of CDI.

Enterococci enhance Clostridioides difficile pathogenesis

Enteric pathogens are exposed to a dynamic polymicrobial environment in the gastrointestinal tract¹. This microbial community has been shown to be important during infection, but there are few examples illustrating how microbial interactions can influence the virulence of invading pathogens². Here we show that expansion of a group of antibiotic-resistant, opportunistic pathogens in the gut-the enterococci-enhances the fitness and pathogenesis of Clostridioides difficile. Through a parallel process of nutrient restriction and cross-feeding, enterococci shape the metabolic environment in the gut and reprogramme C. difficile metabolism. Enterococci provide fermentable amino acids, including leucine and ornithine, which increase C. difficile fitness in the antibiotic-perturbed gut. Parallel depletion of arginine by enterococci through arginine catabolism provides a metabolic cue for C. difficile that facilitates increased virulence. We find evidence of microbial interaction between these two pathogenic organisms in multiple mouse models of infection and patients infected with C. difficile. These findings provide mechanistic insights into the role of pathogenic microbiota in the susceptibility to and the severity of C. difficile infection.