Integrated Meta-omics Reveals a Fungus-Associated Bacteriome and Distinct Functional Pathways in Clostridioides difficile Infection

The role of gut fungi in Clostridioides difficile infection

Clostridioides difficile, the etiological agent of C. difficile infection (CDI), elicits a spectrum of diarrheal symptoms with varying severity and the potential to result in severe complications such as colonic perforation, pseudomembranous colitis, and toxic megacolon. The perturbation of gut microbiome, often triggered by antibiotic usage, represents the primary factor augmenting the risk of CDI. This underscores the significance of interactions between C. difficile and the microbiome in determining pathogen adaptability. In recent years, researchers have increasingly recognized the pivotal role played by intestinal microbiota in host health and its therapeutic potential as a target for medical interventions. While extensive evidence has been established regarding the involvement of gut bacteria in CDI, our understanding of symbiotic interactions between hosts and fungi within intestinal microbiota remains limited. Herein, we aim to comprehensively elucidate both composition and key characteristics of gut fungal communities that significantly contribute to CDI, thereby enhancing our comprehension from pharmacological and biomarker perspectives while exploring their prospective therapeutic applications for CDI.

The role of single and mixed biofilms in Clostridioides difficile infection and strategies for prevention and inhibition

Clostridioides difficile infection (CDI) is a serious disease with a high recurrence rate. The single and mixed biofilms formed by C. difficile in the gut contribute to the formation of recurrent CDI (rCDI). In parallel, other gut microbes influence the formation and development of C. difficile biofilms, also known as symbiotic biofilms. Interactions between members within the symbiotic biofilm are associated with the worsening or alleviation of CDI. These interactions include effects on C. difficile adhesion and chemotaxis, modulation of LuxS/AI-2 quorum sensing (QS) system activity, promotion of cross-feeding by microbial metabolites, and regulation of intestinal bile acid and pyruvate levels. In the process of C. difficile biofilms control, inhibition of C. difficile initial biofilm formation and killing of C. difficile vegetative cells and spores are the main targets of action. The role of symbiotic biofilms in CDI suggested that targeting interventions of C. difficile-promoting gut microbes could indirectly inhibit the formation of C. difficile mixed biofilms and improved the ultimate therapeutic effect. In summary, this review outlines the mechanisms of C. difficile biofilm formation and summarises the treatment strategies for such single and mixed biofilms, aiming to provide new ideas for the prevention and treatment of CDI.

Clostridioides difficile infection is associated with differences in transcriptionally active microbial communities

Clostridioides difficile infection (CDI) is responsible for around 300,000 hospitalizations yearly in the United States, with the associated monetary cost being billions of dollars. Gut microbiome dysbiosis is known to be important to CDI. To the best of our knowledge, metatranscriptomics (MT) has only been used to characterize gut microbiome composition and function in one prior study involving CDI patients. Therefore, we utilized MT to investigate differences in active community diversity and composition between CDI+ (n = 20) and CDI- (n = 19) samples with respect to microbial taxa and expressed genes. No significant (Kruskal-Wallis, p > 0.05) differences were detected for richness or evenness based on CDI status. However, clustering based on CDI status was significant for both active microbial taxa and expressed genes datasets (PERMANOVA, p ≤ 0.05). Furthermore, differential feature analysis revealed greater expression of the opportunistic pathogens Enterocloster bolteae and Ruminococcus gnavus in CDI+ compared to CDI- samples. When only fungal sequences were considered, the family Saccharomycetaceae expressed more genes in CDI-, while 31 other fungal taxa were identified as significantly (Kruskal-Wallis p ≤ 0.05, log(LDA) ≥ 2) associated with CDI+. We also detected a variety of genes and pathways that differed significantly (Kruskal-Wallis p ≤ 0.05, log(LDA) ≥ 2) based on CDI status. Notably, differential genes associated with biofilm formation were expressed by C. difficile. This provides evidence of another possible contributor to C. difficile's resistance to antibiotics and frequent recurrence in vivo. Furthermore, the greater number of CDI+ associated fungal taxa constitute additional evidence that the mycobiome is important to CDI pathogenesis. Future work will focus on establishing if C. difficile is actively producing biofilms during infection and if any specific fungal taxa are particularly influential in CDI.

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.

Therapeutic Approach Targeting Gut Microbiome in Gastrointestinal Infectious Diseases

While emerging evidence highlights the significance of gut microbiome in gastrointestinal infectious diseases, treatments like Fecal Microbiota Transplantation (FMT) and probiotics are gaining popularity, especially for diarrhea patients. However, the specific role of the gut microbiome in different gastrointestinal infectious diseases remains uncertain. There is no consensus on whether gut modulation therapy is universally effective for all such infections. In this comprehensive review, we examine recent developments of the gut microbiome's involvement in several gastrointestinal infectious diseases, including infection of Helicobacter pylori, Clostridium difficile, Vibrio cholerae, enteric viruses, Salmonella enterica serovar Typhimurium, Pseudomonas aeruginosa Staphylococcus aureus, Candida albicans, and Giardia duodenalis. We have also incorporated information about fungi and engineered bacteria in gastrointestinal infectious diseases, aiming for a more comprehensive overview of the role of the gut microbiome. This review will provide insights into the pathogenic mechanisms of the gut microbiome while exploring the microbiome's potential in the prevention, diagnosis, prediction, and treatment of gastrointestinal infections.

Gut Microbiota Associated with Clostridioides difficile Carriage in Three Clinical Groups (Inflammatory Bowel Disease, C. difficile Infection and Healthcare Workers) in Hospital Field

Clostridioides difficile is an anaerobic spore-forming Gram-positive bacterium. C. difficile carriage and 16S rDNA profiling were studied in three clinical groups at three different sampling times: inflammatory bowel disease (IBD) patients, C. difficile infection (CDI) patients and healthcare workers (HCWs). Diversity analysis was realized in the three clinical groups, the positive and negative C. difficile carriage groups and the three analysis periods. Concerning the three clinical groups, β-diversity tests showed significant differences between them, especially between the HCW group and IBD group and between IBD patients and CDI patients. The Simpson index (evenness) showed a significant difference between two clinical groups (HCWs and IBD). Several genera were significantly different in the IBD patient group (Sutterella, Agathobacter) and in the CDI patient group (Enterococcus, Clostridioides). Concerning the positive and negative C. difficile carriage groups, β-diversity tests showed significant differences. Shannon, Simpson and InvSimpson indexes showed significant differences between the two groups. Several genera had significantly different relative prevalences in the negative group (Agathobacter, Sutterella, Anaerostipes, Oscillospira) and the positive group (Enterococcus, Enterobacteriaceae_ge and Enterobacterales_ge). A microbiota footprint was detected in C. difficile-positive carriers. More experiments are needed to test this microbiota footprint to see its impact on C. difficile infection.

Faecalibacterium: a bacterial genus with promising human health applications

In humans, many diseases are associated with alterations in gut microbiota, namely increases or decreases in the abundance of specific bacterial groups. One example is the genus Faecalibacterium. Numerous studies have underscored that low levels of Faecalibacterium are correlated with inflammatory conditions, with inflammatory bowel disease (IBD) in the forefront. Its representation is also diminished in the case of several diseases, including colorectal cancer (CRC), dermatitis, and depression. Additionally, the relative presence of this genus is considered to reflect, at least in part, intestinal health status because Faecalibacterium is frequently present at reduced levels in individuals with gastrointestinal diseases or disorders. In this review, we first thoroughly describe updates to the taxonomy of Faecalibacterium, which has transformed a single-species taxon to a multispecies taxon over the last decade. We then explore the links discovered between Faecalibacterium abundance and various diseases since the first IBD-focused studies were published. Next, we examine current available strategies for modulating Faecalibacterium levels in the gut. Finally, we summarize the mechanisms underlying the beneficial effects that have been attributed to this genus. Together, epidemiological and experimental data strongly support the use of Faecalibacterium as a next-generation probiotic (NGP) or live biotherapeutic product (LBP).

Bacterial, fungal, and interkingdom microbiome features of exclusively breastfeeding dyads are associated with infant age, antibiotic exposure, and birth mode

The composition and function of early life gut bacterial communities (microbiomes) have been proposed to modulate health for the long term. In addition to bacteria, fungi (mycobiomes) also colonize the early life gut and have been implicated in health disorders such as asthma and obesity. Despite the potential importance of mycobiomes in health, there has been a lack of study regarding fungi and their interkingdom interactions with bacteria during infancy. The goal of this study was to obtain a more complete understanding of microbial communities thought to be relevant for the early life programming of health. Breastmilk and infant feces were obtained from a unique cohort of healthy, exclusively breastfeeding dyads recruited as part of the Mothers and Infants Linked for Healthy Growth (MILk) study with microbial taxa characterized using amplicon-based sequencing approaches. Bacterial and fungal communities in breastmilk were both distinct from those of infant feces, consistent with niche-specific microbial community development. Nevertheless, overlap was observed among sample types (breastmilk, 1-month feces, 6-month feces) with respect to the taxa that were the most prevalent and abundant. Self-reported antibacterial antibiotic exposure was associated with micro- as well as mycobiome variation, which depended upon the subject receiving antibiotics (mother or infant), timing of exposure (prenatal, peri- or postpartum), and sample type. In addition, birth mode was associated with bacterial and fungal community variation in infant feces, but not breastmilk. Correlations between bacterial and fungal taxa abundances were identified in all sample types. For infant feces, congruency between bacterial and fungal communities was higher for older infants, consistent with the idea of co-maturation of bacterial and fungal gut communities. Interkingdom connectedness also tended to be higher in older infants. Additionally, higher interkingdom connectedness was associated with Cesarean section birth and with antibiotic exposure for microbial communities of both breastmilk and infant feces. Overall, these results implicate infant age, birth mode, and antibiotic exposure in bacterial, fungal and interkingdom relationship variation in early-life-relevant microbiomes, expanding the current literature beyond bacteria.

Multi-omics analysis of biomarkers and molecular mechanism of rheumatoid arthritis with bone destruction

OBJECTIVES

Our study aimed to elucidate the role of metabolites, bacteria, and fungi in rheumatoid arthritis (RA) patients with bone destruction (BD(+)) and identify some biomarkers to predicate bone progression of RA.

METHODS

Plasma metabolites of the 127 RA patients and 69 healthy controls were conducted by using nontargeted liquid chromatography-mass spectrometry (LC-MS). The gut bacteria and fungi were assessed by 16S rRNA and internal transcribed spacer (ITS).

RESULTS

Compared with RA patients without bone destruction (BD(-)), some metabolites, bacteria, and fungi were altered in BD(+). Seven metabolites were selected as key metabolites for classifying the BD(+) and BD(-) groups with moderate accuracy (AUC=0.71). Metabolites-groups, metabolites-metabolites, and metabolites-clinical factors had a certain correlation, and 7 metabolites were enriched in glycerophospholipid metabolism and L-arginine and proline metabolism pathways. The bacteria and fungi of the BD(+) group showed significant differences in composition and function compared with BD(-) group. The changed 4 bacteria and 12 fungi yielded accuracy (AUC=0.74 and AUC=0.87, respectively) for the two groups. Taking 7 metabolites, 4 bacteria, and 12 fungi as a panel for AUC analysis, an improved AUC of 0.99 significantly discriminated the two groups. The changed metabolites, gut bacteria, and fungi may affect the pathway related to L-arginine.

CONCLUSIONS

Our nontargeted LC-MS, 16S rRNA, and ITS highlighted a novel link among the metabolites, bacteria, fungi, and pathology of BD(+), which could contribute to our understanding of the role of metabolites, bacteria, and fungi in BD(+) etiology and offered some novel biomarkers to predict the bone progression of RA.

Analysis of Intestinal Mycobiota of Patients with Clostridioides difficile Infection among a Prospective Inpatient Cohort

Clostridioides difficile infection (CDI) is a burden to health care systems worldwide. Gut microbiota dysbiosis associated with CDI has been well accepted. However, contribution of fungal mycobiota to CDI has recently gained research interest. Here, we report the gut mycobiota composition of 149 uniquely well characterized participants from a prospective clinical cohort and evaluate the discriminating ability of gut mycobiota to classify CDI and non-CDI patients. Fecal samples were divided into two groups: (i) CDI (inpatients who had clinically significant diarrhea and positive nucleic acid amplification testing [NAAT] and received subsequent CDI therapy, n = 58) and (ii) non-CDI, which can be further divided into three subgroups: (a) carrier (inpatients with positive stool NAAT but without diarrhea; n = 28); (b) diarrhea (inpatients with negative stool NAAT; n = 31); and (c) control (inpatients with negative stool NAAT and without diarrhea; n = 32). Fecal mycobiota composition was analyzed by internal transcribed spacer 2 (ITS2) sequencing. In comparison to non-CDI patients, CDI patients tend to have gut mycobiota with lower biodiversity, weaker fungi correlations, and weaker correlations between fungi and host immune factors. Notably, 11 genera (Saccharomyces, Penicillium, Aspergillus, Cystobasidium, Cladosporium, and so on) were significantly enriched in non-CDI patients, and Pichia and Suhomyces were enriched in patients with CDI, while 1 two genera, Cystobasidium and Exophiala, had higher abundance in patients with diarrhea compared with CDI (linear discriminant analysis [LDA] > 3.0; P < 0.05). Ascomycota and Basidiomycota (or Candida and Saccharomyces) exhibited a strong negative correlation (r ≤ -0.714 or r ≤ -0.387; P < 0.05), and the ratios of Ascomycota to Basidiomycota or genera Candida to Saccharomyces were dramatically higher in CDI patients than in non-CDI patients (P < 0.05). A disease-specific pattern with much weaker fungal abundance correlations was observed in the CDI group compared to that in the non-CDI and diarrhea groups, suggesting that these correlations may contribute to the development of CDI. Our findings provided specific markers of stool fungi that distinguish CDI from all non-CDI hospitalized patients. This study's potential clinical utility for better CDI diagnosis warrants further investigation. IMPORTANCE Clostridioides difficile is an opportunistic bacterial pathogen that causes a serious and potentially life-threatening infection of the human gut. It remains an existing challenge to distinguish active infection of CDI from diarrhea with non-CDI causes. A few large prospective studies from recent years suggest that there is no single optimal test for the diagnosis of CDI. Previous research has concentrated on the relationship between bacteria and CDI, while the roles of fungi, as a significant proportion of the gut microbial ecosystem, remain understudied. In this study, we report a series of fungal markers that may add diagnostic values for the development of a more systematic approach to accurate CDI diagnosis. These results help open the door for better understanding of the relationship between host immune factors and the fungal community in the context of CDI pathogenesis.

Gut Microbiota Composition Associated with Clostridioides difficile Colonization and Infection

Clostridioides difficile is an anaerobic Gram-positive and spore-forming bacterium. The majority of C. difficile strains produce two toxins, A and B, associated with the development of acute diarrhea and/or colitis. In this review, two situations are distinguished: C. difficile infection (CDI) and asymptomatic colonization (AC). The main objective of this review is to explore the available data related to the link between the gut microbiota and the development of CDI. The secondary aim is to provide more information on why some people colonized with toxigenic C. difficile develop an infection while others show no signs of disease. Several factors, such as the use of antibiotics and proton pump inhibitors, hospitalization, and age, predispose individuals to C. difficile colonization and/or C. difficile infection. The gut microbiota of people with AC showed decreased abundances of Prevotella, Alistipes, Bacteroides, Bifidobacterium, Dorea, Coprococcus, and Roseburia. The gut microbiota of people suffering from CDI showed reductions in the abundances of Lachnospiraceae, Ruminococcaceae, Blautia spp., Prevotella spp., Dialister spp., Bifidobacterium spp., Roseburia spp., Anaerostipes spp., Faecalibacterium spp. and Coprococcus spp., in comparison with healthy people. Furthermore, increases in the abundances of Enterococcaceae and Enterococcus were associated with C. difficile infection.

Loss-of-function SLC30A2 mutants are associated with gut dysbiosis and alterations in intestinal gene expression in preterm infants

Loss of Paneth cell (PC) function is implicated in intestinal dysbiosis, mucosal inflammation, and numerous intestinal disorders, including necrotizing enterocolitis (NEC). Studies in mouse models show that zinc transporter ZnT2 (SLC30A2) is critical for PC function, playing a role in granule formation, secretion, and antimicrobial activity; however, no studies have investigated whether loss of ZnT2 function is associated with dysbiosis, mucosal inflammation, or intestinal dysfunction in humans. SLC30A2 was sequenced in healthy preterm infants (26-37 wks; n = 75), and structural analysis and functional assays determined the impact of mutations. In human stool samples, 16S rRNA sequencing and RNAseq of bacterial and human transcripts were performed. Three ZnT2 variants were common (>5%) in this population: H346Q, f = 19%; L293R, f = 7%; and a previously identified compound substitution in Exon7, f = 16%). H346Q had no effect on ZnT2 function or beta-diversity. Exon7 impaired zinc transport and was associated with a fractured gut microbiome. Analysis of microbial pathways suggested diverse effects on nutrient metabolism, glycan biosynthesis and metabolism, and drug resistance, which were associated with increased expression of host genes involved in tissue remodeling. L293R caused profound ZnT2 dysfunction and was associated with overt gut dysbiosis. Microbial pathway analysis suggested effects on nucleotide, amino acid and vitamin metabolism, which were associated with the increased expression of host genes involved in inflammation and immune response. In addition, L293R was associated with reduced weight gain in the early postnatal period. This implicates ZnT2 as a novel modulator of mucosal homeostasis in humans and suggests that genetic variants in ZnT2 may affect the risk of mucosal inflammation and intestinal disease.

What is unknown in using microbiota as a therapeutic?

Fecal microbiota transplantation (FMT) has been used extensively in the treatment of various gastrointestinal and extraintestinal conditions, despite that there are still a lot of missing gaps in our knowledge in the gut microbiota and its behavior. This article describes the unknowns in microbiota biology (undetected microbes, uncertain colonization, unclear mechanisms of action, uncertain indications, unsure long-term efficacy, or side effects). We discuss how these unknowns may affect the therapeutic uses of FMT, and the potentials and caveats of other related microbiota-based therapies. When used as an experimental therapy or last resort in difficult conditions, caution should be taken against inadvertent complications. Clear documentations of post-treatment events should be made mandatory, classified, and graded as in clinical trials. Further robust scientific experiments and properly designed clinical studies are needed.

Gut Microbial Alterations in Diarrheal Baer's Pochards (Aythya baeri)

The structure and composition of gut microbiota correlate with the occurrence and development of host health and disease. Diarrhea can cause alterations in gut microbiota in animals, and the changes in the gut microbial structure and composition may affect the development of diarrhea. However, there is a scarcity of information on the effects of diarrhea on gut fungal composition and structure, particularly in Baer's pochard (Aythya baeri). The current study was performed for high-throughput sequencing of the fungal-specific internal transcribed spacer 1 (ITS-1) to detect the differences of gut mycobiota in healthy and diarrheal Baer's pochard. Results showed that the gut mycobiota not only decreased significantly in diversity but also in structure and composition. Statistical analysis between two groups revealed a significant decrease in the abundance of phylum Rozellomycota, Zoopagomycota, Mortierellomycota, and Kickxellomycota in diarrheal Baer's pochard. At the genus levels, fungal relative abundance changed significantly in 95 genera, with 56 fungal genera, such as Wickerhamomyces, Alternaria, Penicillium, Cystofilobasidium, and Filobasidium, increasing significantly in the gut of the diarrheal Baer's pochard. In conclusion, the current study revealed the discrepancy in the gut fungal diversity and community composition between the healthy and diarrheal Baer's pochard, laying the basis for elucidating the relationship between diarrhea and the gut mycobiota in Baer's pochard.

The role of gut mycobiome in health and diseases

The gut microbiome comprised of microbes from multiple kingdoms, including bacteria, fungi, and viruses. Emerging evidence suggests that the intestinal fungi (the gut "mycobiome") play an important role in host immunity and inflammation. Advances in next generation sequencing methods to study the fungi in fecal samples and mucosa tissues have expanded our understanding of gut fungi in intestinal homeostasis and systemic immunity in health and their contribution to different human diseases. In this review, the current status of gut mycobiome in health, early life, and different diseases including inflammatory bowel disease, colorectal cancer, and metabolic diseases were summarized.

Wolf in Sheep's Clothing: Clostridioides difficile Biofilm as a Reservoir for Recurrent Infections

The microbiota inhabiting the intestinal tract provide several critical functions to its host. Microorganisms found at the mucosal layer form organized three-dimensional structures which are considered to be biofilms. Their development and functions are influenced by host factors, host-microbe interactions, and microbe-microbe interactions. These structures can dictate the health of their host by strengthening the natural defenses of the gut epithelium or cause disease by exacerbating underlying conditions. Biofilm communities can also block the establishment of pathogens and prevent infectious diseases. Although these biofilms are important for colonization resistance, new data provide evidence that gut biofilms can act as a reservoir for pathogens such as Clostridioides difficile. In this review, we will look at the biofilms of the intestinal tract, their contribution to health and disease, and the factors influencing their formation. We will then focus on the factors contributing to biofilm formation in C. difficile, how these biofilms are formed, and their properties. In the last section, we will look at how the gut microbiota and the gut biofilm influence C. difficile biofilm formation, persistence, and transmission.

Fecal Mycobiota Combined With Host Immune Factors Distinguish Clostridioides difficile Infection From Asymptomatic Carriage

BACKGROUND & AIMS

Although the role of gut microbiota in Clostridioides difficile infection (CDI) has been well established, little is known about the role of mycobiota in CDI. Here, we performed mycobiome data analysis in a well-characterized human cohort to evaluate the potential of using gut mycobiota features for CDI diagnosis.

METHODS

Stool samples were collected from 118 hospital patients, divided into 3 groups: CDI (n = 58), asymptomatic carriers (Carrier, n = 28), and Control (n = 32). The nuclear ribosomal DNA internal transcribed spacer 2 was sequenced using the Illumina HiSeq platform to assess the fungal composition. Downstream statistical analyses (including Alpha diversity analysis, ordination analysis, differential abundance analysis, fungal correlation network analysis, and classification analysis) were then performed.

RESULTS

Significant differences were observed in alpha and beta diversity between patients with CDI and Carrier (P < .05). Differential abundance analysis identified 2 genera (Cladosporium and Aspergillus) enriched in Carrier. The ratio of Ascomycota to Basidiomycota was dramatically higher in patients with CDI than in Carrier and Control (P < .05). Correlations between host immune factors and mycobiota features were weaker in patients with CDI than in Carrier. Using 4 fungal operational taxonomic units combined with 6 host immune markers in the random forest classifier can achieve very high performance (area under the curve ∼92.38%) in distinguishing patients with CDI from Carrier.

CONCLUSIONS

Our study provides specific markers of stool fungi combined with host immune factors to distinguish patients with CDI from Carrier. It highlights the importance of gut mycobiome in CDI, which may have been underestimated. Further studies on the diagnostic applications and therapeutic potentials of these findings are warranted.

Gut microbiota composition in health-care facility-and community-onset diarrheic patients with Clostridioides difficile infection

The role of gut microbiota in the establishment and development of Clostridioides difficile infection (CDI) has been widely discussed. Studies showed the impact of CDI on bacterial communities and the importance of some genera and species in recovering from and preventing infection. However, most studies have overlooked important components of the intestinal ecosystem, such as eukaryotes and archaea. We investigated the bacterial, archaea, and eukaryotic intestinal microbiota of patients with health-care-facility- or community-onset (HCFO and CO, respectively) diarrhea who were positive or negative for CDI. The CDI-positive groups (CO/+, HCFO/+) showed an increase in microorganisms belonging to Bacteroidetes, Firmicutes, Proteobacteria, Ascomycota, and Opalinata compared with the CDI-negative groups (CO/-, HCFO/-). Patients with intrahospital-acquired diarrhea (HCFO/+, HCFO/-) showed a marked decrease in bacteria beneficial to the intestine, and there was evidence of increased Archaea and Candida and Malassezia species compared with the CO groups (CO/+, CO/-). Characteristic microbiota biomarkers were established for each group. Finally, correlations between bacteria and eukaryotes indicated interactions among the different kingdoms making up the intestinal ecosystem. We showed the impact of CDI on microbiota and how it varies with where the infection is acquired, being intrahospital-acquired diarrhea one of the most influential factors in the modulation of bacterial, archaea, and eukaryotic populations. We also highlight interactions between the different kingdoms of the intestinal ecosystem, which need to be evaluated to improve our understanding of CDI pathophysiology.

Debaryomyces, the Achilles heel of wound repair

In a recent Science paper, Jain et al. (2021) discover that a fungus contributes to delayed wound healing in mice and is enriched in inflamed tissue from Crohn's disease patients. This culprit is not a well-known pathogen, but cheese yeast Debaryomyces hansenii, highlighting the importance of further studying fungi-host interactions.

Gut mycobiome: The probable determinative role of fungi in IBD patients

Inflammatory bowel disease (IBD) is a multi-factorial autoimmune disorder that its causative agents are unknown. The gut microbiota comprises of bacteria, viruses, fungi and protozoa that its role in IBD has remained controversially. Bacteria constitute more than 99% of the gut microbiota composition, and the main core of the gut microbiota is composed from Bacteroidetes and Firmicutes. The gut microbiota plays an important role in training, development and haemostasis of the immune responses during the life. Fungi compose a very small portion of gut microbiota, but play determinative roles in homeostasis of the gut bacterial composition and the mucosal immune responses. An interkingdom correlation between bacteria and fungi has been suggested. For example, the presence of Salmonella enterica serovar Typhimurium reduces the viability and colonisation of C albicans. Alterations in the composition and function of the gut microbiota, which is known as dysbiosis, are a usual event in patients who suffer from IBD. Although the main reason for this alteration is not clear, the interaction between gut bacteria and gut fungi seems to be an important subject in IBD patients. This review covers new findings on the interaction between fungi and bacteria and the role of fungi in the pathophysiology of IBD.

Long-Term Bacterial and Fungal Dynamics following Oral Lyophilized Fecal Microbiota Transplantation in Clostridioides difficile Infection

Clostridioides difficile infection (CDI) is a substantial health concern worldwide, complicated by patterns of increasing antibiotic resistance that may impact primary treatment. Orally administered fecal microbiota transplantation (FMT) is efficacious in the management of recurrent CDI, with specific bacterial species known to influence clinical outcomes.

Oral lyophilized fecal microbiota transplantation (FMT) is effective in recurrent Clostridioides difficile infection (CDI); however, limited data exist on its efficacy in primary CDI and long-term microbial engraftment. Patients with primary or recurrent CDI were prospectively enrolled to receive oral FMT. Changes in the bacterial and fungal communities were characterized prior to and up to 6 months following treatment. A total of 37 patients with CDI (15 primary, 22 recurrent) were treated with 6 capsules each containing 0.35-g lyophilized stool extract. A total of 33 patients (89%) had sustained CDI cure, of whom 3 required a second course. There were no safety signals identified. FMT significantly increased bacterial diversity and shifted composition toward donor profiles in responders but not in nonresponders, with robust donor contribution observed to 6 months following FMT (P < 0.001). Responders showed consistent decreases in Enterobacteriaceae and increases in Faecalibacterium sp. to levels seen in donors. Mycobiome profiling revealed an association with FMT failure and increases in one Penicillium taxon, as well as coexclusion relationships between Candida sp. and bacterial taxa enriched in both donors and responders. Primary CDI was associated with more robust changes in the bacterial community than those with recurrent disease. Oral FMT leads to durable microbial engraftment in patients with primary and recurrent CDI, with several microbial taxa being associated with therapy outcome. Novel coexclusion relationships between bacterial and fungal species support the clinical relevance of transkingdom dynamics.

IMPORTANCEClostridioides difficile infection (CDI) is a substantial health concern worldwide, complicated by patterns of increasing antibiotic resistance that may impact primary treatment. Orally administered fecal microbiota transplantation (FMT) is efficacious in the management of recurrent CDI, with specific bacterial species known to influence clinical outcomes. To date, little is known about the efficacy of FMT in primary CDI and the impact of the mycobiome on therapeutic outcomes. We performed matched bacterial and fungal sequencing on longitudinal samples from a cohort of patients treated with oral FMT for primary and recurrent CDI. We validated many bacterial signatures following oral therapy, confirmed engraftment of donor microbiome out to 6 months following therapy, and demonstrated coexclusion relationships between Candida albicans and two bacterial species in the gut microbiota, which has potential significance beyond CDI, including in the control of gut colonization by this fungal species.

The Initial Gut Microbiota and Response to Antibiotic Perturbation Influence Clostridioides difficile Clearance in Mice

Clostridioides difficile is a leading nosocomial infection. Although perturbation to the gut microbiota is an established risk, there is variation in who becomes asymptomatically colonized, develops an infection, or has adverse infection outcomes. Mouse models of C. difficile infection (CDI) are widely used to answer a variety of C. difficile pathogenesis questions. However, the interindividual variation between mice from the same breeding facility is less than what is observed in humans. Therefore, we challenged mice from 6 different breeding colonies with C. difficile. We found that the starting microbial community structures and C. difficile persistence varied by the source of mice. Interestingly, a subset of the bacteria that varied across sources were associated with how long C. difficile was able to colonize. By increasing the interindividual diversity of the starting communities, we were able to better model human diversity. This provided a more nuanced perspective of C. difficile pathogenesis.

The gut microbiota has a key role in determining susceptibility to Clostridioides difficile infections (CDIs). However, much of the mechanistic work examining CDIs in mouse models uses animals obtained from a single source. We treated mice from 6 sources (2 University of Michigan colonies and 4 commercial vendors) with clindamycin, followed by a C. difficile challenge, and then measured C. difficile colonization levels throughout the infection. The microbiota were profiled via 16S rRNA gene sequencing to examine the variation across sources and alterations due to clindamycin treatment and C. difficile challenge. While all mice were colonized 1 day postinfection, variation emerged from days 3 to 7 postinfection with animals from some sources colonized with C. difficile for longer and at higher levels. We identified bacteria that varied in relative abundance across sources and throughout the experiment. Some bacteria were consistently impacted by clindamycin treatment in all sources of mice, including Lachnospiraceae, Ruminococcaceae, and Enterobacteriaceae. To identify bacteria that were most important to colonization regardless of the source, we created logistic regression models that successfully classified mice based on whether they cleared C. difficile by 7 days postinfection using community composition data at baseline, post-clindamycin treatment, and 1 day postinfection. With these models, we identified 4 bacterial taxa that were predictive of whether C. difficile cleared. They varied across sources (Bacteroides) or were altered by clindamycin (Porphyromonadaceae) or both (Enterobacteriaceae and Enterococcus). Allowing for microbiota variation across sources better emulates human interindividual variation and can help identify bacterial drivers of phenotypic variation in the context of CDIs.

IMPORTANCEClostridioides difficile is a leading nosocomial infection. Although perturbation to the gut microbiota is an established risk, there is variation in who becomes asymptomatically colonized, develops an infection, or has adverse infection outcomes. Mouse models of C. difficile infection (CDI) are widely used to answer a variety of C. difficile pathogenesis questions. However, the interindividual variation between mice from the same breeding facility is less than what is observed in humans. Therefore, we challenged mice from 6 different breeding colonies with C. difficile. We found that the starting microbial community structures and C. difficile persistence varied by the source of mice. Interestingly, a subset of the bacteria that varied across sources were associated with how long C. difficile was able to colonize. By increasing the interindividual diversity of the starting communities, we were able to better model human diversity. This provided a more nuanced perspective of C. difficile pathogenesis.

Fecal transplants as a microbiome-based therapeutic

Impaired microbiome diversity and composition can develop into a potent etiological agent of disease and increase susceptibility to infection. Given this, interventions targeting the microbiome have developed rapidly, with healthy donor feces being a de facto source of beneficial communities employed to rebalance patients' microbiomes. Recent evidence has demonstrated that bacterial and viral richness, short chain fatty acid production, bile acid conversion as well as presence of bacterial and fungal pathobionts are associated with therapy efficacy; however, little is known of the influence of host factors such as genetics, medications, and diet. Here, current knowledge on factors associated with fecal transplant efficacy, as well as efforts to transition to other forms of therapy are reviewed.

Minority report: the intestinal mycobiota in systemic infections

Compared to bacteria, fungi often exhibit a lower abundance and a higher temporal volatility in the intestinal microbiota. Analysis of fungi in the microbiota (mycobiota) faces technical limitations with tools that were originally developed for analyzing bacteria. Dysbiotic states of the intestinal mycobiota, often associated with disruption of the healthy bacterial microbiota, are characterized by overgrowth (domination) of specific fungal taxa and loss of diversity. Intestinal domination by Candida species has been shown to be a major source of Candida bloodstream infections. Fungal dysbiosis is also linked to the development and treatment response in non-fungal infections, for example Clostridioides difficile colitis and HIV. Further research is needed to define the contribution of intestinal mycobiota to human fungal and non-fungal infections.