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PubMed2026

Genome-sequencing-based benchmarking of antimicrobial resistance, treatment outcomes and healthcare transmission events for Clostridioides difficile infection in Australian hospitals.

BACKGROUND: Clostridioides difficile infection (CDI) remains a priority for infection prevention and control in health care, particularly with the emergence of hypervirulent strains and antimicrobial resistance (AMR). AIM: To characterize the genomic epidemiology and AMR profiles of culture-confirmed CDI cases within tertiary hospitals in Australia. METHODS: A total of 155 C. difficile isolates from 142 patients with CDI diagnosed in four hospitals between 2023 and 2025 were studied. Data collected included patient demographics, severity of infection, antibiotic treatment and clinical outcomes at 8 weeks. Phenotypic susceptibility to vancomycin, fidaxomicin, metronidazole, moxifloxacin, meropenem, tetracycline and rifaximin were determined by agar dilution. Isolates underwent whole-genome sequencing (WGS) for genotyping and resistome assessment. FINDINGS: WGS differentiated 39 distinct sequence types among CDI isolates across different healthcare services. In total, 100 isolates were singletons and 55 (35% clustering rate) isolates were considered to be genomically related (difference of two or fewer single-nucleotide polymorphisms). Of these, 12 patients (8.5%) with close hospital contact formed six epidemiologically linked clusters. Phenotypic susceptibility results were obtained for 134 (86.4%) CDI isolates. There was no phenotypic resistance to vancomycin [minimum inhibitory concentration required to inhibit the growth of 90% of isolates (MIC90) 1 mg/L], metronidazole (MIC90 0.5 mg/L) or fidaxomicin (MIC90 0.5 mg/L). There was no association in the study cohort between the presence of resistance genes or reduced phenotypic susceptibility and CDI recurrence. CONCLUSION: Genomic analysis of C. difficile isolates did not identify any outbreaks or an association between the sequence type or presence of a resistance gene and clinical outcomes. High-resolution characterization and identification of antibiotic resistance, CDI clinical relapse and recent transmission offered by genome sequencing can provide important benchmarks for hospital infection control.

Antibiotic resistance↗

PubMed2026

Development and validation of a novel LC-MS/MS method for simultaneous quantification of fidaxomicin and metabolite (OP-1118) from feces for gut pharmacobiome studies.

Fidaxomicin is a first-line antibiotic for treating Clostridioides difficile infection. While it has low systemic absorption and reaches high colonic concentrations, it is hydrolyzed to a less active metabolite, OP-1118. Few studies have completely described critical experimental details of liquid chromatography-tandem mass spectrometry (LC-MS/MS) for quantifying fecal fidaxomicin and OP-1118. This study developed and validated a simple, fast, and sensitive LC-MS/MS method to quantify fidaxomicin and OP-1118 in human and mouse feces. This method simplified fecal sample preparation without the use of solid phase extraction and optimized LC-MS/MS parameters. A broad working range (0.3-1000 ng/ml) in both diluted human and murine fecal matrices was achieved with good intra- and inter-day accuracy (93-107%), precision (1-7%), and recovery (70-105%) as well as little IS-normalized matrix effects. This method was utilized to quantify fidaxomicin and OP-1118 in human and murine fecal samples. This novel method was simple, fast, sensitive, and accurate in analyzing fecal fidaxomicin and OP-1118 and could be deployed to facilitate gut pharmacobiome research.

Feces↗

PubMed2025

Fecal microbiota transplantation promotes type 2 mucosal immune responses with colonic epithelium proliferation in patients with recurrent Clostridioides difficile.

BACKGROUNDFecal microbiota transplantation (FMT) is the most effective therapy for recurrent Clostridioides difficile infection (rCDI), yet its mechanism of action remains poorly understood.METHODSWe report the results of a clinical trial of patients undergoing FMT therapy for rCDI (n = 16), which analyzed colon biopsies, plasma, PBMCs, and stool at the time of FMT and 2-month follow-up. Plasma and colon biopsy samples were also collected from healthy controls for comparison with patients with rCDI. Microbiome composition, colonic gene expression, and immune changes were evaluated through high-throughput sequencing and immunoprofiling via flow cytometry.RESULTSNo patients experienced recurrence at follow-up. FMT significantly altered the intestinal microbiome but had no significant impact on the systemic immune system. In contrast, FMT promoted broad changes in colonic transcriptional profiles compared with both pre-FMT and healthy control biopsies, inhibiting genes associated with proinflammatory signaling and upregulating type 2 immunity and proliferative pathways (Myc and mTORC1). FMT increased expression of IL-33 and the type 2 immune EGFR family ligand amphiregulin, potentially explaining upregulation of Myc and mTORC1 pathways. Spatial transcriptomics demonstrated that these changes were localized to the colonic epithelium. Comparison of transcriptional profiles with available single-cell gene sets determined that post-FMT biopsies were enriched in signatures associated with proliferative cell types while repressing signatures of differentiated colonocytes.CONCLUSIONWe conclude that FMT promotes proliferation of the colonic epithelium in patients with rCDI, which may drive regeneration and protect against subsequent CDI.TRIAL REGISTRATIONClinicaltrials.gov NCT02797288.FUNDINGThis work was funded by grants from the NIH.

Adult↗

PubMed2026

Use of Whole Genome Sequencing to Investigate the Risk for Transmission of Clostridioides difficile From Prior Room Occupants: A Single-Center Study.

BACKGROUND: Admission to a room previously occupied by a patient with Clostridioides difficile infection (CDI) has been identified as a risk factor for CDI. However, previous studies have not included molecular typing to definitively link healthcare-associated CDI (HA-CDI) cases to prior room occupants. METHODS: In a hospital and affiliated long-term care facility, we conducted a 1-year cohort study to determine if exposure to a room previously occupied by a CDI patient and/or with environmental contamination after cleaning and disinfection in the past 3 months was associated with an increased risk of HA-CDI. Multivariable logistic regression was used to assess risk factors for HA-CDI. Whole genome sequencing was used to determine the relatedness of HA-CDI isolates and isolates from prior CDI cases or environmental surfaces. RESULTS: Of 5,746 admitted patients, 55 were diagnosed with HA-CDI. Exposure to a room previously occupied by a CDI patient and/or with a positive post-discharge culture was not associated with an increased risk of HA-CDI (adjusted odds ratio 1.15, 95% confidence interval 0.65-1.98; P=0.62). None of the 21 HA-CDI patients with prior room-level exposures were infected with isolates genomically related to isolates from prior room occupants with CDI or from room surfaces. Five HA-CDI cases were linked to prior CDI patients or environmental isolates on the same ward or without ward-level exposure. CONCLUSION: Despite frequent exposure to rooms previously occupied by CDI patients or contaminated with C. difficile, no HA-CDI cases were linked to prior room exposures in a facility using sporicidal disinfectants in CDI rooms.

Clostridioides difficile↗

PubMed2026

Efficacy and safety of pantoprazole for stress-ulcer prophylaxis in critically ill patients: A systematic review and Meta-analysis of randomized controlled trials.

BACKGROUND: Stress-related mucosal damage (SRMD) is common in critically ill patients, and pharmacologic prophylaxis remains essential. This study evaluated the efficacy and safety of pantoprazole for stress-ulcer prophylaxis in ICU patients. MATERIALS AND METHODS: A systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted per PRISMA-2020 guidelines. PubMed, Scopus, and CENTRAL were searched for studies comparing pantoprazole with placebo in adult and pediatric ICU patients. The primary outcome was clinically important gastrointestinal (GI) bleeding; secondary outcomes included mortality, ventilator-associated pneumonia (VAP), and Clostridioides difficile infection. RESULTS: Seven RCTs (n ≈ 9127; pantoprazole = 4575; placebo = 4552) were included. Pantoprazole significantly reduced clinically important GI bleeding (RR = 0.53; 95% CI 0.29-0.94; p = 0.03) without affecting overall mortality (RR ≈ 0.99 [95% CI 0.92-1.05]; p = 0.68). Infection rates were similar between groups (VAP: RR = 0.99; p = 0.78; C. difficile: RR = 1.11; p = 0.73). Sensitivity analyses confirmed robustness. CONCLUSIONS: Pantoprazole effectively reduces clinically important GI bleeding without increasing infection or overall mortality.

Pantoprazole↗

PubMed2026

Metagenome-scale modeling to assess microbiome metabolic complementarity for precision microbiota transplantation therapies.

Fecal microbiota transplantation (FMT) holds therapeutic promise beyond recurrent Clostridioides difficile infection, but clinical outcomes remain unpredictable and donor-selection strategies remain limited, in part because the role of donor‒recipient metabolic interactions in shaping the post-FMT community remains poorly understood. Here, we leverage metagenome-scale metabolic modeling to quantify metabolic niche complementarity between donor and recipient microbiomes and predict post-FMT community composition. Using MICOM-derived metabolic models, we show that donor genomes whose metabolic flux profiles are more dissimilar from the recipient community colonize at significantly higher rates in a murine FMT model. In a human IBS trial, the same metric predicted post-FMT community composition via leave-one-out cross-validation and captured known disease-associated alterations in short-chain fatty acid, sulfur, and gas metabolism. We then performed 2,548 in silico FMT simulations between IBS-D/M patients and donors from the OpenBiome biobank to evaluate personalized donor screening, identifying super-donors characterized by high taxonomic diversity, broad metabolic niche coverage, and community interaction networks dominated by cross-feeding rather than competition. Together, these results support metabolic niche complementarity as a potential determinant of post-FMT community composition and provide a mechanistic basis for evaluating donor-recipient metabolic compatibility. This framework offers a scalable approach for generating testable hypotheses for personalized donor selection.

Fecal Microbiota Transplantation↗

PubMed2026

S-layer-phage interaction in Clostridioides difficile.

Successful infection by a bacteriophage requires the injection of the phage genome into the cytoplasm of the host bacterium. To achieve this, an infecting phage must traverse the layers of the host cell envelope, including the membrane(s) and the cell wall. This process is further complicated in bacterial species that produce a proteinaceous S-layer on the outermost surface of the cell. Surprisingly little is known about the mechanistic basis of these early stages in the phage lifecycle, and even less is known about infection of S-layer producing bacteria. Recent advances in structural biology, particularly in cryoEM, have dramatically improved our understanding of the structures of both bacterial S-layers and phage virions separately, but we still lack a molecular view combining both phage and S-layer in the process of infection. Here, we review our current understanding of phage-S-layer interactions, using the human pathogen Clostridioides difficile as an example host.

Clostridioides difficile↗

PubMed2026

From colonization to infection: Genomic evolution of Clostridioides difficile pathogenesis.

Clostridioides difficile is a spore-forming, toxin-producing anaerobe that is a leading cause of healthcare-associated infections. Its success as a pathogen reflects a complex interplay between bacterial evolution, virulence regulation, ecological adaptation, environmental selection, and host susceptibility. Comparative genomics has revealed deep C. difficile lineage diversification, driven by mobile genetic elements and selective pressures from antibiotics and host environments. These events affect strain-specific virulence by shaping the organization and regulation of the pathogenicity toxin loci, metabolic adaptations for nutrient utilization, and enhanced spore resilience. This review integrates evolutionary and genomic perspectives to illustrate how adaptive diversification has sculpted C. difficile pathogenesis and epidemic success.

CP: microbiology↗

PubMed2026

Longitudinal surveillance of antibiotic resistance and virulence evolution in Clostridioides difficile: a 4-year retrospective study of hospitalized patients in a tertiary hospital in China.

UNLABELLED: Clostridioides difficile (C. difficile) is the primary pathogen responsible for nosocomial infectious diarrhea and pseudomembranous colitis. In China, metronidazole and vancomycin are the preferred treatments for C. difficile infection (CDI). This study aimed to investigate the evolution of vancomycin (VA) and metronidazole (MTZ) resistance, as well as the longitudinal changes in virulence over time, using next-generation sequencing, drug susceptibility tests, and analysis of resistance and virulence genes. Additionally, we monitored the emergence of the highly virulent C. difficile strain RT027 and the spread and potential outbreak of C. difficile in the hospital setting. A random stratified sampling method was used to select 114 fecal samples from inpatients at Affiliated Hangzhou First People's Hospital, School of Medicine, Westlake University, between 2021 and 2024. Clinical data from the enrolled patients were also collected. We conducted antigen and toxin protein detection for C. difficile, strain isolation and identification, drug sensitivity tests, whole genome sequencing, and bioinformatics analysis. This included comparisons of drug resistance genes, detection of toxin genes, and the construction of phylogenetic trees based on pan-genome analysis to investigate the resistance and toxin gene variations in C. difficile. Among the 114 samples collected from Affiliated Hangzhou First People's Hospital, School of Medicine, Westlake University, no vancomycin- or metronidazole-resistant strains were identified. However, the average minimum inhibitory concentration (MIC) of C. difficile to vancomycin increased annually (H = 33.208, P < 0.05). The average MIC of C. difficile to metronidazole was highest in 2022 but decreased in 2023 and 2024 (H = 41.990, P < 0.05). Notably, in 2024, one C. difficile strain exhibited an MIC for metronidazole at the resistance threshold (2.00 μg/mL). Further Spearman correlation analysis of the strain years with drug sensitivity results revealed a positive correlation between strain years and the MIC levels of vancomycin and metronidazole (r = 0.528, P < 0.05; r = 0.377, P < 0.05). The proportion of toxin-producing strains increased annually, with 100% of strains in 2024 producing toxins, representing the highest proportion compared to the previous three years (X² =11.75, P < 0.05). Both vancomycin and metronidazole remain effective for the treatment of CDI in clinical practice. However, the sensitivity of C. difficile to these two drugs is gradually decreasing, and the rate of toxin gene carriage is also rising in clinical cases. No hospital outbreaks of C. difficile infections were identified in this study. IMPORTANCE: Clostridioides difficile has developed resistance to multiple antibiotics, including cephalosporins, clindamycin, and fluoroquinolones. This has exacerbated the global antibiotic resistance crisis. In China, according to current treatment guidelines, vancomycin and metronidazole are the preferred first-line drugs for treating C. difficile infections. However, there are reports indicating the emergence of new resistance to both vancomycin and metronidazole. Although there is extensive research on the long-term antibiotic resistance of C. difficile abroad, research on the continuous monitoring of antibiotic resistance and potential outbreaks of C. difficile in China is relatively limited. To fill this gap, we studied positive C. difficile strains from a tertiary general hospital in China. Through Next-Generation Sequencing (NGS), drug sensitivity testing, and analysis of drug resistance and virulence genes, we revealed the evolution of C. difficile's resistance to vancomycin and metronidazole, as well as changes in virulence, and monitored the spread within the hospital and potential outbreaks of C. difficile.

Humans↗

PubMed2024

Deficiency of IL-22-binding protein enhances the ability of the gut microbiota to protect against enteric pathogens.

Interleukin 22 (IL-22) promotes intestinal barrier integrity, stimulating epithelial cells to enact defense mechanisms against enteric infections, including the production of antimicrobial peptides. IL-22 binding protein (IL-22BP) is a soluble decoy encoded by the Il22ra2 gene that decreases IL-22 bioavailability, attenuating IL-22 signaling. The impact of IL-22BP on gut microbiota composition and functioning is poorly understood. We found that Il22ra2-/- mice are better protected against Clostridioides difficile and Citrobacter rodentium infections. This protection relied on IL-22-induced antimicrobial mechanisms before the infection occurred, rather than during the infection itself. Indeed, the gut microbiota of Il22ra2-/- mice mitigated infection of wild-type (WT) mice when transferred via cohousing or by cecal microbiota transplantation. Indicator species analysis of WT and Il22ra2-/- mice with and without cohousing disclosed that IL22BP deficiency yields a gut bacterial composition distinct from that of WT mice. Manipulation of dietary fiber content, measurements of intestinal short-chain fatty acids and oral treatment with acetate disclosed that resistance to C. difficile infection is related to increased production of acetate by Il22ra2-/--associated microbiota. Together, these findings suggest that IL-22BP represents a potential therapeutic target for those at risk for or with already manifest infection with this and perhaps other enteropathogens.

Animals↗

PubMed2015

Clostridium difficile Infections after Blunt Trauma: A Different Patient Population?

BACKGROUND: The epidemiology of Clostridium difficile-associated infection (CDI) has changed, and it is evident that susceptibility is related not only to exposures and bacterial potency, but host factors as well. Several small studies have suggested that CDI after trauma is associated with a different patient phenotype. The purpose of this study was to examine and describe the epidemiologic factors associated with C. difficile in blunt trauma patients without traumatic brain injury using the Trauma-Related Database as a part of the "Inflammation and Host Response to Injury" (Glue Grant) and the University of Florida Integrated Data Repository. METHODS: Previously recorded baseline characteristics, clinical data, and outcomes were compared between groups (67 C. difficile and 384 uncomplicated, 813 intermediate, and 761 complicated non-C. difficile patients) as defined by the Glue Grant on admission and at days seven and 14. RESULTS: The majority of CDI patients experienced complicated or intermediate clinical courses. The mean ages of all cohorts were less than 65 y and CDI patients were significantly older than uncomplicated patients without CDI. The CDI patients had increased days in the hospital and on the ventilator, as well as significantly higher new injury severity scores (NISS), and a greater percentage of patients with NISS >34 points compared with non-CDI patients. They also had greater Marshall and Denver multiple organ dysfunction scores than non-CDI uncomplicated patients, and greater creatinine, alkaline phosphatase, neutrophil count, lactic acid, and PiO2:FiO2 compared with all non-CDI cohorts on admission. In addition, the CDI patients had higher glucose concentrations and base deficit from uncomplicated patients and greater leukocytosis than complicated patients on admission. Several of these changes persisted to days seven and 14. CONCLUSION: Analysis of severe blunt trauma patients with C. difficile, as compared with non-CDI patients, reveals evidence of increased inflammation, immunosuppression, worse acute kidney injury, higher NISS, greater days in the hospital and on the ventilator, higher organ injury scores, and prolonged clinical courses. This supports reports of an increased prevalence of CDI in a younger population not believed previously to be at risk. This unique population may have specific genomic or inflammation-related risk factors that may play more important roles in disease susceptibility. Prospective analysis may allow early identification of at-risk patients, creation of novel therapeutics, and improved understanding of how and why C. difficile colonization transforms into infection after severe blunt trauma.

Adolescent↗

PubMed2025

Unique growth and morphology properties of Clade 5 Clostridioides difficile strains revealed by single-cell time-lapse microscopy.

Clostridioides difficile is a gastrointestinal pathogen of both humans and agricultural animals and thus a major One Health threat. The C. difficile species consists of five main clades, with Clade 5 currently undergoing speciation from Clades 1-4. Since Clade 5 strains are highly prevalent in agricultural animals and a frequent cause of zoonotic infections, these strains may have evolved phenotypes that distinguish them from Clade 1-4 strains. Here, we compare the growth properties of Clade 5 strains to those of Clade 1-4 strains using anaerobic time-lapse microscopy coupled with automated image analysis. Our analyses indicate that Clade 5 strains grow faster and are more likely to form long chains of cells than Clade 1-4 strains. Using comparative genomic and CRISPRi analyses, we show that the chaining phenotype of Clade 5 strains is driven by the orientation of the invertible cmr switch sequence, with chaining strains exhibiting a bias to the cmr-ON state. Interestingly, Clade 5 strains with a bias towards the cmr-ON state shifted to a largely cmr-OFF state during murine infection, suggesting that the cmr-OFF state is under positive selection during infection. Collectively, our data reveal that Clade 5 strains have distinct growth properties, which may allow them to inhabit diverse ecological niches.

Clostridioides difficile↗

PubMed2026

Naturally Occurring CodY Variants Alter Ligand Binding, DNA Target Affinity, and Virulence in Clostridioides difficile.

Clostridioides difficile is an important nosocomial pathogen and is the major cause of antibiotic-associated diarrhea and colitis. CodY is a global transcriptional regulator that coordinates metabolism and virulence in Gram-positive pathogens by sensing branched-chain amino acids and GTP. In C. difficile, CodY represses toxin production by inhibiting transcription of tcdR and by influencing c-di-GMP turnover. Here, we characterized two naturally occurring CodY variants, CodY(Y146N) and CodY(V58A), whose substitutions lie near the GTP- and ILV-binding sites, respectively. GTP-binding by CodY(Y146N) was severely compromised, while leucine binding was enhanced; CodY(V58A) showed reduced leucine binding. Both variants exhibited reduced ligand-dependent binding to the tcdR promoter and failed to repress toxin production as effectively as CodY(WT). Expression of virulence-associated genes (tcdR, pdcB) was elevated in strains producing either variant. In a hamster infection model, both variant-producing strains were significantly more virulent than the CodY(WT) strain. These findings demonstrate that single amino acid substitutions in this global regulator can alter ligand affinity and promoter binding, potentially rewiring gene regulatory networks to enhance the pathogenic potential of C. difficile.

Clostridioides difficile↗

PubMed2025

Unique growth and morphology properties of Clade 5 Clostridioides difficile strains revealed by single-cell time-lapse microscopy.

Clostridioides difficile is a gastrointestinal pathogen of both humans and agricultural animals and thus a major One Health threat. The C. difficile species consists of five main clades, with Clade 5 currently undergoing speciation from Clades 1-4. Clade 5 strains are highly prevalent in agricultural animals and can cause zoonotic infections, suggesting that these strains have evolved phenotypes that distinguish them from Clade 1-4 strains. Here, we compare the growth properties of Clade 5 strains to those of Clade 1-4 strains using anaerobic time-lapse microscopy coupled with automated image analysis. Our analyses indicate that Clade 5 strains grow faster and are more likely to form long chains of cells than Clade 1-4 strains. Using comparative genomic and CRISPRi analyses, we show that the chaining phenotype of Clade 5 strains is driven by the orientation of the invertible cmr switch sequence, with chaining strains exhibiting a bias to the cmr-ON state. Interestingly, Clade 5 strains with a bias towards the cmr-ON state shifted to a largely cmr-OFF state during murine infection, suggesting that the cmr-OFF state is under positive selection during infection. Collectively, our data reveal that Clade 5 strains have distinct growth properties, which may allow them to inhabit diverse ecological niches.

Journal Article↗

PubMed2026

A single DNA methylation site regulates cell fate during Clostridioides difficile sporulation.

DNA methylation is a widespread phenomenon in bacteria that can regulate gene expression, although the mechanisms underlying this epigenetic regulation are often poorly understood. In Clostridioides difficile, the orphan DNA methyltransferase CamA promotes sporulation, a process critical for the persistence and transmission of this nosocomial pathogen. However, the specific CamA target genes that drive this increased sporulation phenotype were unknown. Here, we show that methylation of a single CamA motif in the promoter region of spoIIE, which encodes a factor critical for activating the early-acting sporulation sigma factor, σF, is sufficient to promote spoIIE transcription, σF activation, and spore formation. Surprisingly, the CamA-dependent increase in spoIIE expression also increases the frequency with which cells prematurely activate σF prior to asymmetric division, resulting in miscompartmentalized σF activity. While this premature activation event triggers cell lysis in the well-studied spore-former Bacillus subtilis, we show that C. difficile cells retain developmental plasticity: predivisional cells that have prematurely activated σF can abort sporulation and resume vegetative growth, whereas cells that activate σF in the forespore after asymmetric division remain committed to sporulation. Thus, DNA methylation controls a critical cell fate decision in C. difficile without compromising its capacity to adapt to fluctuating environmental conditions. Finally, we show that CamA confers a significant fitness advantage during murine infection through mechanisms largely independent of its ability to promote sporulation. Since CamA is specific to C. difficile and epigenetically regulates multiple pathways critical for pathogen persistence, these analyses imply that CamA could be a promising antimicrobial target.

DNA Methylation↗

PubMed2026

Resistome and microbiome-immune interactions in an Eastern European population with high antibiotic use.

The gut microbiome influences host health, affecting gastrointestinal, metabolic, immune, cardiovascular, and neurological functions. A balanced microbiome is associated with favorable health outcomes. However, excessive antibiotic use and dietary habits can disrupt this ecosystem, leading to dysbiosis and affecting body homeostasis. This first comprehensive metagenomic analysis of the gut microbiome in a healthy Romanian cohort, a population underrepresented in microbiome studies and characterized by high antibiotic consumption, addresses a gap in current microbiome research. We report an enrichment of Enterobacteriaceae although overall composition is more comparable to other European than non-European cohorts. Community configurations align with established enterotype patterns, and our analysis provides insight into their relationship with within-phylum diversity. The analysis of antimicrobial resistance provides insight into the prevalence of resistance genes within this reservoir. We specifically report the presence of cfr(E), a Clostridioides difficile gene, and tet(X5), a variant from the ubiquitous tet family, genes not previously reported in healthy European populations. Integration with data from the European Centre for Disease Prevention and Control links the overall prevalence of resistance genes in this reservoir to antibiotic classes with higher community consumption in this population, notably beta-lactams and quinolones, highlighting potential targets for antibiotic stewardship programs. Finally, we investigate the relationship between the microbial profile and the systemic immune responses, inferred from correlations with in vitro cytokine production. Notably, we identify potential immune-priming roles for Collinsella, Flavonifractor, and Bifidobacterium species.IMPORTANCEThis first comprehensive study of the healthy gut microbiome in a Romanian cohort addresses a gap in current microbiome research, dominated by data sets from a limited number of regions. It sets a baseline for the microbiome and resistome composition of this population, and, while definitions of "healthy" microbiomes, or baseline resistomes, remain lacking, such study helps contextualize future studies and support the monitoring of dynamics. The Enterobacteriaceae abundance suggests a microbiome composition potentially influenced by antimicrobial consumption, a relevant pattern in a region with a high burden of nosocomial infections. In addition, the prevalence of antimicrobial resistance genes and the concordance with commonly used antibiotics in the community reinforce the need to address antibiotic use in public health strategies. Although gut microbiome-immunity relationships remain incompletely understood, our findings support a role for microbiome composition in immune-related traits and provide a valuable resource for future studies.

Humans↗

PubMed2026

Dichalcogenide Fidaxomicin Derivatives to Probe Thiol-Mediated Uptake into Bacteria.

The natural product fidaxomicin (Fdx) is a narrow-spectrum antibiotic clinically prescribed for the treatment of Clostrodioides difficile infections. However, limited cellular uptake reduces its therapeutic potential, particularly against Gram-negative bacteria and mycobacteria. In this study, we investigated Thiol-Mediated Uptake (TMU) to promote the delivery of Fdx into bacterial cells. We synthesized a library of Fdx derivatives bearing cyclic dichalcogenide moieties and evaluated their antimicrobial properties against C. difficile and Mycobacterium tuberculosis, respectively. Remarkably, the synthetic Fdx derivatives retained strong levels of antibacterial activity, and the disulfide-containing analogs outperformed their all-carbon control counterparts in many instances. We then developed a systematic study to investigate the mechanistic impact of the introduced disulfide functionalities by conducting experiments with TMU inhibitors and quantifying intracellular accumulation in Mycobacterium bovis BCG, a model organism for M. tuberculosis, via LC-MS/MS. While complete disentanglement of the factors influencing activity was not feasible, features such as compound stability and lipophilicity were identified as significant contributors. Overall, the superior performance of disulfide analogs suggests that differences in cellular entry or intracellular processing, potentially related to TMU, are involved. This work highlights that TMU remains a viable approach for modulating the uptake of therapeutic agents into bacterial cells.

Sulfhydryl Compounds↗