Colonization Resistance Research Articles

Exogenous butyrate inhibits butyrogenic metabolism and alters virulence phenotypes in Clostridioides difficile.

The gut microbiome engenders colonization resistance against the diarrheal pathogen Clostridioides difficile, but the molecular basis of this colonization resistance is incompletely understood. A prominent class of gut microbiome-produced metabolites important for colonization resistance against C. difficile is short-chain fatty acids (SCFAs). In particular, one SCFA (butyrate) decreases the fitness of C. difficile in vitro and is correlated with C. difficile-inhospitable gut environments, both in mice and in humans. Here, we demonstrate that butyrate-dependent growth inhibition in C. difficile occurs under conditions where C. difficile also produces butyrate as a metabolic end product. Furthermore, we show that exogenous butyrate is internalized into C. difficile cells and is incorporated into intracellular CoA pools where it is metabolized in a reverse (energetically unfavorable) direction to crotonyl-CoA and (S)-3-hydroxybutyryl-CoA and/or 4-hydroxybutyryl-CoA. This internalization of butyrate and reverse metabolic flow of a butyrogenic pathway(s) in C. difficile coincides with alterations in toxin release and sporulation. Together, this work highlights butyrate as a marker of a C. difficile-inhospitable environment to which C. difficile responds by releasing its diarrheagenic toxins and producing environmentally resistant spores necessary for transmission between hosts. These findings provide foundational data for understanding the molecular and genetic basis of how C. difficile growth is inhibited by butyrate and how butyrate alters C. difficile virulence in the face of a highly competitive and dynamic gut environment.IMPORTANCEThe gut microbiome engenders colonization resistance against the diarrheal pathogen Clostridioides difficile, but the molecular basis of this colonization resistance is incompletely understood, which hinders the development of novel therapeutic interventions for C. difficile infection (CDI). We investigated how C. difficile responds to butyrate, an end-product of gut microbiome community metabolism which inhibits C. difficile growth. We show that exogenously produced butyrate is internalized into C. difficile, which inhibits C. difficile growth by interfering with its own butyrate production. This growth inhibition coincides with increased toxin release from C. difficile cells and the production of environmentally resistant spores necessary for transmission between hosts. Future work to disentangle the molecular mechanisms underlying these growth and virulence phenotypes will likely lead to new strategies to restrict C. difficile growth in the gut and minimize its pathogenesis during CDI.

In vivo evaluation of Clostridioides difficile enoyl-ACP reductase II (FabK) inhibition by phenylimidazole unveils a promising narrow-spectrum antimicrobial strategy.

Clostridioides difficile infection (CDI) is a leading cause of hospital-acquired diarrhea, which often stems from disruption of the gut microbiota by broad-spectrum antibiotics. The increasing prevalence of antibiotic-resistant C. difficile strains, combined with disappointing clinical trial results for recent antibiotic candidates, underscores the urgent need for novel CDI antibiotics. To this end, we investigated C. difficile enoyl ACP reductase (CdFabK), a crucial enzyme in de novo fatty acid synthesis, as a drug target for microbiome-sparing antibiotics. To test this concept, we evaluated the efficacy and in vivo spectrum of activity of the phenylimidazole analog 296, which is validated to inhibit intracellular CdFabK. Against major CDI-associated ribotypes 296 had an Minimum inhibitory concentration (MIC90) of 2 µg/mL, which was comparable to vancomycin (1 µg/mL), a standard of care antibiotic. In addition, 296 achieved high colonic concentrations and displayed dosed-dependent efficacy in mice with colitis CDI. Mice that were given 296 retained colonization resistance to C. difficile and had microbiomes that resembled the untreated mice. Conversely, both vancomycin and fidaxomicin induced significant changes to mice microbiomes, in a manner consistent with prior reports. CdFabK, therefore, represents a potential target for microbiome-sparing CDI antibiotics, with phenylimidazoles providing a good chemical starting point for designing such agents.

Impact of Plasmodium relictum Infection on the Colonization Resistance of Bird Gut Microbiota: A Preliminary Study.

Avian malaria infection has been known to affect host microbiota, but the impact of Plasmodium infection on the colonization resistance in bird gut microbiota remains unexplored. This study investigated the dynamics of Plasmodium relictum infection in canaries, aiming to explore the hypothesis that microbiota modulation by P. relictum would reduce colonization resistance. Canaries were infected with P. relictum, while a control group was maintained. The results revealed the presence of P. relictum in the blood of all infected canaries. Analysis of the host microbiota showed no significant differences in alpha diversity metrics between infected and control groups. However, significant differences in beta diversity indicated alterations in the microbial taxa composition of infected birds. Differential abundance analysis identified specific taxa with varying prevalence between infected and control groups at different time points. Network analysis demonstrated a decrease in correlations and revealed that P. relictum infection compromised the bird microbiota's ability to resist the removal of taxa but did not affect network robustness with the addition of new nodes. These findings suggest that P. relictum infection reduces gut microbiota stability and has an impact on colonization resistance. Understanding these interactions is crucial for developing strategies to enhance colonization resistance and maintain host health in the face of parasitic infections.

CPX-351 exploits the gut microbiota to promote mucosal barrier function, colonization resistance, and immune homeostasis

AbstractCPX-351, a liposomal combination of cytarabine plus daunorubicin, has been approved for the treatment of adults with newly diagnosed, therapy-related acute myeloid leukemia (AML) or AML with myelodysplasia-related changes, because it improves survival and outcome of patients who received hematopoietic stem cell transplant compared with the continuous infusion of cytarabine plus daunorubicin (referred to as “7 + 3” combination). Because gut dysbiosis occurring in patients with AML during induction chemotherapy heavily affects the subsequent phases of therapy, we have assessed whether the superior activity of CPX-351 vs “7 + 3” combination in the real-life setting implicates an action on and by the intestinal microbiota. To this purpose, we have evaluated the impact of CPX-351 and “7 + 3” combination on mucosal barrier function, gut microbial composition and function, and antifungal colonization resistance in preclinical models of intestinal damage in vitro and in vivo and fecal microbiota transplantation. We found that CPX-351, at variance with “7 + 3” combination, protected from gut dysbiosis, mucosal damage, and gut morbidity while increasing antifungal resistance. Mechanistically, the protective effect of CPX-351 occurred through pathways involving both the host and the intestinal microbiota, namely via the activation of the aryl hydrocarbon receptor–interleukin-22 (IL-22)–IL-10 host pathway and the production of immunomodulatory metabolites by anaerobes. This study reveals how the gut microbiota may contribute to the good safety profile, with a low infection-related mortality, of CPX-351 and highlights how a better understanding of the host-microbiota dialogue may contribute to pave the way for precision medicine in AML.

Nutrition of Escherichia coli within the intestinal microbiome.

In this chapter, we update our 2004 review of "The Life of Commensal Escherichia coli in the Mammalian Intestine" (https://doi.org/10.1128/ecosalplus.8.3.1.2), with a change of title that reflects the current focus on "Nutrition of E. coli within the Intestinal Microbiome." The earlier part of the previous two decades saw incremental improvements in understanding the carbon and energy sources that E. coli and Salmonella use to support intestinal colonization. Along with these investigations of electron donors came a better understanding of the electron acceptors that support the respiration of these facultative anaerobes in the gastrointestinal tract. Hundreds of recent papers add to what was known about the nutrition of commensal and pathogenic enteric bacteria. The fact that each biotype or pathotype grows on a different subset of the available nutrients suggested a mechanism for succession of commensal colonizers and invasion by enteric pathogens. Competition for nutrients in the intestine has also come to be recognized as one basis for colonization resistance, in which colonized strain(s) prevent colonization by a challenger. In the past decade, detailed investigations of fiber- and mucin-degrading anaerobes added greatly to our understanding of how complex polysaccharides support the hundreds of intestinal microbiome species. It is now clear that facultative anaerobes, which usually cannot degrade complex polysaccharides, live in symbiosis with the anaerobic degraders. This concept led to the "restaurant hypothesis," which emphasizes that facultative bacteria, such as E. coli, colonize the intestine as members of mixed biofilms and obtain the sugars they need for growth locally through cross-feeding from polysaccharide-degrading anaerobes. Each restaurant represents an intestinal niche. Competition for those niches determines whether or not invaders are able to overcome colonization resistance and become established. Topics centered on the nutritional basis of intestinal colonization and gastrointestinal health are explored here in detail.

The microbial metabolite urolithin A reduces Clostridioides difficile toxin expression and toxin-induced epithelial damage.

Clostridioides difficile is a Gram-positive, anaerobic, spore-forming bacterium responsible for antibiotic-associated pseudomembranous colitis. Clostridioides difficile infection (CDI) symptoms can range from diarrhea to life-threatening colon damage. Toxins produced by C. difficile (TcdA and TcdB) cause intestinal epithelial injury and lead to severe gut barrier dysfunction, stem cell damage, and impaired regeneration of the gut epithelium. Current treatment options for intestinal repair are limited. In this study, we demonstrate that treatment with the microbial metabolite urolithin A (UroA) attenuates CDI-induced adverse effects on the colon epithelium in a preclinical model of CDI-induced colitis. Moreover, our analysis suggests that UroA treatment protects against C. difficile-induced inflammation, disruption of gut barrier integrity, and intestinal tight junction proteins in the colon of CDI mice. Importantly, UroA treatment significantly reduced the expression and release of toxins from C. difficile without inducing bacterial cell death. These results indicate the direct regulatory effects of UroA on bacterial gene regulation. Overall, our findings reveal a novel aspect of UroA activity, as it appears to act at both the bacterial and host levels to protect against CDI-induced colitis pathogenesis. This research sheds light on a promising avenue for the development of novel treatments for C. difficile infection.IMPORTANCETherapy for Clostridioides difficile infections includes the use of antibiotics, immunosuppressors, and fecal microbiota transplantation. However, these treatments have several drawbacks, including the loss of colonization resistance, the promotion of autoimmune disorders, and the potential for unknown pathogens in donor samples. To date, the potential benefits of microbial metabolites in CDI-induced colitis have not been fully investigated. Here, we report for the first time that the microbial metabolite urolithin A has the potential to block toxin production from C. difficile and enhance gut barrier function to mitigate CDI-induced colitis.

Клиническое значение интегральной регистрации маркеров эндотоксического иммунитета и колонизационной резистентности буккальных эпителиоцитов при рецидивирующем бронхите у подростков

Recurrent bronchitis (RB) occupies one of the key places in the structure of nonspecific diseases of the respiratory tract and remains a significant medical and social problem in healthcare. The purpose — to investigate and evaluate the clinical significance of integral registration of markers of endotoxic immunity and colonization resistance of buccal epithelial cells (BE) in RB in adolescents. Material and methods. The study included 117 children (12–17 years old), including 78 with RB — the main group, 29 with acute bronchitis (AB) — the comparison group and 23 conditionally healthy children — the control group. The analysis of anamnestic, clinical, paraclinical data, verification of etiologically significant viruses, registration of artificial colonization of buccal epithelial cells (BE), colonization index (CI), micro-LAL test were carried out. Statistical processing of the results was carried out using the SPSS program. Results. A significant difference in markers of colonization resistance and anti-endotoxin protection was revealed in recurrent inflammation in the respiratory tract in comparison with AB in peers. In RB, the initial degree of Candida albicans adhesion to BE was significantly higher in relation to AB (p = 0.0427) and upon discharge from the hospital did not reach normative values, being significantly different from patients with AB (p = 0.0391). The high index of artificial colonization indicates the activation of allochthonous flora and disruption of the microbiota in the oral cavity, which negatively affects the body reactivity. In patients with RB, the titer of antiglycolipid antibodies significantly decreased and in 75% the values did not return to normal, while in AB they did not differ from the control. High levels of endotoxin were noted in RB compared to AB (p = 0.0317). Such patients were diagnosed with a more severe course of the disease with symptoms of endogenous intoxication and a long hospitalization period. Using the method of correlation analysis, a high direct relationship was established between artificial colonization and endotoxin concentration (r = 0.71). The relationship between these parameters in AB was significantly less pronounced (r = 0.3). The results obtained indicate close integration and mutual modulation of the local oral immunity and antiendotoxin defense. Conclusion. Integral registration of the markers of reactivity of specific anti-endotoxin immunity and colonization resistance reflect the severe inflammatory process in the respiratory tract and predict the risk of a chronic pathological process in the bronchopulmonary system.

Modeling the effects of prebiotic interventions on luminal and mucosa-associated gut microbiota without and with Clostridium difficile challenge in vitro.

Prebiotics can modulate the gut microbial community composition and function for improved (gut) health and increase resilience against infections. In vitro models of the gut facilitate the study of intervention effects on the gut microbial community relevant to health. The mucosa-associated gut microbiota, which thrives in close contact with the host plays a pivotal role in colonization resistance and health. Therefore, we here introduce the Mi-screen, an experimental approach implementing a 96-well plate equipped with a mucus agar layer for the additional culturing of mucosa-associated microbiota in vitro. In this study, we screened the effects of 2'-Fucosyllactose (2'-FL), fructooligosaccharides (FOS), and inulin within a complex microbiota without and with infection with the C. difficile strains ATCC 43599 (Ribotype 001) or ATCC BAA-1870 (Ribotype 027). We analyzed the microbial community composition and short-chain fatty acid levels after 48 h of incubation. The inclusion of an additional substrate and surface in the form of the mucus agar layer allowed us to culture a microbial richness ranging between 100-160 in Chao index, with Shannon indices of 5-6 across culture conditions, indicative of a microbial diversity of physiological relevance. The mucus agar layer stimulated the growth of characteristic mucosa-associated bacteria such as Roseburia inulinovorans. The prebiotic interventions affected luminal and mucosal microbial communities cultured in vitro and stimulated short-chain fatty acid production. FOS, inulin and 2'-FL promoted the growth of Bifidobacterium adolescentis within the mucosa-associated microbiota cultured in vitro. When spiking the untreated conditions with pathogenic C. difficile, the strains thrived within the luminal and the mucosal sample types, whereas prebiotic treatments exhibited inhibitory effects on C. difficile growth and prevented colonization. In conclusion, the Mi-screen facilitates the screening of luminal and mucosa-associated gut microbial community dynamics in vitro and therefore fills an important gap in the field of in vitro modeling.

Extracellular Proteins Isolated from L. acidophilus as an Osteomicrobiological Therapeutic Agent to Reduce Pathogenic Biofilm Formation, Regulate Chronic Inflammation, and Augment Bone Formation In Vitro.

Periprosthetic joint infection (PJI) is a challenging complication that can occur following joint replacement surgery. Efficacious strategies to prevent and treat PJI and its recurrence remain elusive. Commensal bacteria within the gut convey beneficial effects through a defense strategy named "colonization resistance" thereby preventing pathogenic infection along the intestinal surface. This blueprint may be applicable to PJI. The aim is to investigate Lactobacillus acidophilus spp. and their isolated extracellular-derived proteins (LaEPs) on PJI-relevant Staphylococcus aureus, methicillin-resistant S. aureus, and Escherichia coli planktonic growth and biofilm formation in vitro. The effect of LaEPs on cultured macrophages and osteogenic, and adipogenic human bone marrow-derived mesenchymal stem cell differentiation is analyzed. Data show electrostatically-induced probiotic-pathogen species co-aggregation and pathogenic growth inhibition together with LaEP-induced biofilm prevention. LaEPs primemacrophages for enhanced microbial phagocytosis via cathepsin K, reduce lipopolysaccharide-induced DNA damage and receptor activator nuclear factor-kappa B ligand expression, and promote a reparative M2 macrophage morphology under chronic inflammatory conditions. LaEPs also significantly augment bone deposition while abating adipogenesis thus holding promise as a potential multimodal therapeutic strategy. Proteomic analyses highlight high abundance of lysyl endopeptidase, and urocanate reductase. Further, in vivo analyses are warranted to elucidate their role in the prevention and treatment of PJIs.

Differences in the gut microbiota between Gurkhas and soldiers of British origin.

Previous work indicated that the incidence of travellers' diarrhoea (TD) is higher in soldiers of British origin, when compared to soldiers of Nepalese descent (Gurkhas). We hypothesise that the composition of the gut microbiota may be a contributing factor in the risk of developing TD in soldiers of British origin. This study aimed to characterise the gut microbial composition of Gurkha and non-Gurkha soldiers of the British Army. Recruitment of 38 soldiers (n = 22 Gurkhas, n = 16 non-Gurkhas) and subsequent stool collection, enabled shotgun metagenomic sequencing-based analysis of the gut microbiota. The microbiota of Gurkhas had significantly (P < 0.05) lower diversity, for both Shannon and Simpson diversity indices, using species level markers than the gut microbiota of non-Gurkha soldiers. Non-metric Multidimensional Scaling (NMDS) of the Bray-Curtis distance matrix revealed a significant difference in the composition of the gut microbiota between Gurkhas and non-Gurkha soldiers, at both the species level (P = 0.0178) and the genus level (P = 0.0483). We found three genera and eight species that were significantly enriched in the non-Gurkha group and one genus (Haemophilus) and one species (Haemophilus parainfluenzae) which were enriched in the Gurkha group. The difference in the microbiota composition between Gurkha soldiers and soldiers of British origin may contribute to higher colonization resistance against diarrhoeal pathogens in the former group. Our findings may enable further studies into interventions that modulate the gut microbiota of soldiers to prevent TD during deployment.

Metabolomic signatures of intestinal colonization resistance against Campylobacter jejuni in mice.

Campylobacter jejuni stands out as one of the leading causes of bacterial enteritis. In contrast to humans, specific pathogen-free (SPF) laboratory mice display strict intestinal colonization resistance (CR) against C. jejuni, orchestrated by the specific murine intestinal microbiota, as shown by fecal microbiota transplantation (FMT) earlier. Murine infection models, comprising SPF, SAB, hma, and mma mice were employed. FMT and microbiota depletion were confirmed by culture and culture-independent analyses. Targeted metabolome analyses of fecal samples provided insights into the associated metabolomic signatures. In comparison to hma mice, the murine intestinal microbiota of mma and SPF mice (with CR against C. jejuni) contained significantly elevated numbers of lactobacilli, and Mouse Intestinal Bacteroides, whereas numbers of enterobacteria, enterococci, and Clostridium coccoides group were reduced. Targeted metabolome analysis revealed that fecal samples from mice with CR contained increased levels of secondary bile acids and fatty acids with known antimicrobial activities, but reduced concentrations of amino acids essential for C. jejuni growth as compared to control animals without CR. The findings highlight the role of microbiota-mediated nutrient competition and antibacterial activities of intestinal metabolites in driving murine CR against C. jejuni. The study underscores the complex dynamics of host-microbiota-pathogen interactions and sets the stage for further investigations into the mechanisms driving CR against enteric infections.

Dynamics of morphofunctional parameters in experimental pseudomonosis of rabbits

Among the most frequently reported diseases of rabbits, the main place is occupied by diseases of bacterial etiology, the pathogens of which are characterized by multidrug resistance. The aim of the study was to analyze the dynamics of morphometric indicators during experimental infection of rabbits with Pseudomonas aeruginosa bacteria. When assessing colonization resistance of organs, the following indicators were taken into account: colonization index, ratio of the number of microorganisms isolated from nasal cavity washes, contents of cecum of clinically healthy and sick animals. Significant changes in morphological parameters (p 0.05) were revealed during the isolation of P. aeruginosa from blood, lymph nodes, spleen, liver, and kidneys of sick rabbits. Overgrowth of isolates producing adhesive antigens, hemolysins, bacteriocins should be considered as prognostic markers of connective tissue dysplasia. The initiation, development, and outcome of microbial overgrowth syndrome are mediated by morphofunctional changes in compensatory mechanisms of mucociliary clearance system and colonization resistance.

Microbiome diversity protects against pathogens by nutrient blocking.

The human gut microbiome plays an important role in resisting colonization of the host by pathogens, but we lack the ability to predict which communities will be protective. We studied how human gut bacteria influence colonization of two major bacterial pathogens, both in vitro and in gnotobiotic mice. Whereas single species alone had negligible effects, colonization resistance greatly increased with community diversity. Moreover, this community-level resistance rested critically upon certain species being present. We explained these ecological patterns through the collective ability of resistant communities to consume nutrients that overlap with those used by the pathogen. Furthermore, we applied our findings to successfully predict communities that resist a novel target strain. Our work provides a reason why microbiome diversity is beneficial and suggests a route for the rational design of pathogen-resistant communities.

Lactobacillus paracasei R3 Alleviates Tumor Progression in Mice with Colorectal Cancer.

Lactobacillus paracasei (L. paracasei), a common probiotic lactobacillus, has important functions in the food industry and human health. However, different strains of L. paracasei inevitably show differences in activity and colonization resistance, leading to differentiation in their functions, as well as their physical or chemical properties. The purpose of this study was to evaluate the characteristics of L. paracasei R3 (L.p R3) isolated from healthy human feces and determine whether the criteria for edible probiotics is met. The hemolysis type, biofilm-forming ability, antibiotic susceptibility, toxicity, and effective activity of L.p R3 were determined by establishing its probiotic activity traits in vitro and in vivo. The results showed that L.p R3 had a moderate biofilm formation ability, was sensitive to 11 antibiotics, was resistant to eight antibiotics, and was not hemolytic. The culture characteristics, morphology, and biochemical responses of the strain were consistent with the seed batch characteristics. In toxicity assays, L.p R3-fed mice showed no abnormalities in body weight, growth, or various organs. Additionally, L.p R3 was found to be effective in the prevention and treatment of colorectal cancer. In conclusion, our results revealed that L.p R3 has potential value as an edible probiotic without toxic side effects and alleviated the tumor progression of colorectal cancer in mice.

Identification of proteoforms of short open reading frame-encoded peptides in Blautia producta under different cultivation conditions.

Short open reading frames (sORF) have the potential to encode small proteins, sORF-encoded peptides (SEP), which are less than or equal to 100 amino acids in length. These SEP have been associated with various physiological processes and are known for their potential roles in modulating immune responses, signaling pathways, and cellular functions. Using bottom-up and top-down proteomics, we identified 45 novel and formerly reported SEP under different growth conditions and stress exposure in single cultures of Blautia producta that plays a central role in mediating colonization resistance and dampening inflammation in the human gut microbiome. Top-down analysis improved identification confidence and allowed the detection of a number of full-length and N- or C-terminal truncated proteoforms of the SEP and of proteoforms carrying post-translational modifications such as disulfides, which provides hints for a wide functional potential of these molecules. The identification of the SEP in single cultures of this bacterium shows that, in contrast to previous results, the biosynthesis of specific SEP is not restricted to direct bacterial interactions within the microbiome but is dependent on growth and environmental conditions during cultivation. IMPORTANCE The identification of short open reading frame-encoded peptides (SEP) and different proteoforms in single cultures of gut microbes offers new insights into a largely neglected part of the microbial proteome landscape. This is of particular importance as SEP provide various predicted functions, such as acting as antimicrobial peptides, maintaining cell homeostasis under stress conditions, or even contributing to the virulence pattern. They are, thus, taking a poorly understood role in structure and function of microbial networks in the human body. A better understanding of SEP in the context of human health requires a precise understanding of the abundance of SEP both in commensal microbes as well as pathogens. For the gut beneficial B. producta, we demonstrate the importance of specific environmental conditions for biosynthesis of SEP expanding previous findings about their role in microbial interactions.

Changes in colonization resistance and composition of the microflora of the colon cavity of white rats with oral administration of calcium acetylacetonate

Annotation. The purpose of the study is to experimentally reveal the effect of calcium acetylacetonate at a dose of 250 mg/kg on colonization resistance and on changes in the composition of the microflora of the colon cavity of white rats 8 hours after its single administration directly into the stomach. The experiment was conducted on 34 outbred white rats weighing 200-220 g, divided into two groups. The control group was not administered calcium acetylacetonate. The microbiological research method is applied. It was found that alcium acetylacetonate at a dose of 250 mg/kg leads not only to changes in the qualitative composition of the microbiota of the contents of the colon cavity, but also to significant changes in the quantitative composition and deep changes in the relationships between the representatives of the main microbiota, as well as taxa of additional and residual microflora. Thus, the population level of the most physiologically useful bacteria of the genus Bifidobacterium, bacteria of the genus Lactobacillus (by 57.4%), Bacteroides (by 21.5%), Escherichia (by 40.5%). The above dose of calcium acetylacetonate contributes to the elimination from the colon cavity of representatives of the main microbiota – bacteria of the genera Eubacterium, Peptostreptococcus, Enterococcus, as well as transient streptobacteria, which exhibit significant antagonistic activity against pathogenic and opportunistic enterobacteria, staphylococci, and others. Based on the obtained data, there is a need for research aimed at the search and selection of agents that have a decontaminating and regulatory effect on the qualitative composition of the microbiota of the colon cavity after oral ingestion of calcium acetylacetonate.

The Relationship Between the Microbiome and Antimicrobial Resistance.

Antibiotics have benefitted human health since their introduction nearly a century ago. However, the rise of antibiotic resistance may portend the dawn of the "post-antibiotic age." With the narrow pipeline for novel antimicrobials, we need new approaches to deal with the rise of multidrug resistant organisms. In the last 2 decades, the role of the intestinal microbiota in human health has been acknowledged and studied widely. Of the various activities carried out by the gut microbiota, colonization resistance is a key function that helps maintain homeostasis. Therefore, re-establishing a healthy microbiota is a novel strategy for treating drug resistance organisms. Preliminary studies suggest that this is a viable approach. However, the extent of their success still needs to be examined. Herein, we will review work in this area and suggest where future studies can further investigate this method for dealing with the threat of antibiotic resistance.

Enhanced in-vitro anti-Candida efficacy of Euphorbia milii Des Moul mediated copper nanoparticles against clinically isolated Candida albicans.

Emergence of fungi as a pathogenic threat presents a significant challenge to public health, notably in intensive care units (ICUs) and among immunocompromised patients. Various factors, including sepsis-induced barrier disruptions, immune system dysfunction, and extremes of age, contribute to increased susceptibility to fungal infections. Hospital practices, such as prolonged surgeries, broad-spectrum antibiotic use, and invasive procedures, further exacerbate the risk. Fungal bloodstream infections, particularly those caused by Candida albicans, rank among the most common hospital-acquired infections, leading to substantial morbidity and mortality. The global rise in invasive candidiasis, particularly due to non-albicans Candida species, presents challenges in the diagnosis and treatment due to nonspecific symptoms and emerging antifungal resistance. Nanotechnology interventions particularly by utilizing green synthesized copper nanoparticles could possibly provide a novel solution to combat microbial colonization, biofilm formation, and drug resistance. This study aimed to assess the prevalence of candidemia, identify the distribution of causative Candida species, and understand their susceptibility patterns to commonly used antifungal agents for effective management in ICU settings. Additionally, the study sought to explore the in vitro anti-Candida activity of green copper nanoparticles synthesized using Euphorbia milii des moul extract. This study was conducted at Microbiology Laboratory of Maharishi Markandeshwar Institute of Medical Sciences and Research from January to December 2022, focused on ICU patients suspected of bloodstream infections. Blood samples were collected aseptically and processed using BD BACTECTM culture vials. Identification of organisms was performed via the Vitek-2 system by confirming candidemia with positivity in both blood samples. After that antifungal susceptibility testing was also performed against Clinical and Laboratory Standards Institute recommended antifungal drug using Vitek 2 system. G-CuNPs were synthesized using E. milii Des moul extract and possessed for physiochemical characterization. The anti-Candida activity of G-CuNPs was evaluated through the MTT assay and time kill assay. After that generation of intracellular reactive oxygen species and DNA degradation were evaluated to understand its mechanism. This study identified a candidemia rate of 7.3% (58/789). Age and gender analysis revealed higher Candida colonization rates in individuals above 60 years old and females. Antifungal sensitivity profiling indicated notable resistance to fluconazole (27.59%) and voriconazole (25.86%). Synthesizing G-CuNPs using E. milii des moul extract represents a novel approach exhibiting significant fungicidal potency against clinically isolated C. albicans, supporting potential therapeutic applications. the findings concluded that synthesized G-CuNPs have tremendous potential to battle against medical device-borne infections by surface coating.

286. The Effect of Fecal Microbiota Transplantation on Decolonization of Multidrug-resistant Organisms in the gut

Abstract Background Gut colonization of multidrug-resistant organisms (MDROs), such as carbapenemase-producing Enterobacteriaceae (CPE) and vancomycin-resistant Enterococci (VRE), precedes clinical infections. It increases the risk of patient-to-patient transmission of MDROs as well as clinical infections such as bacteremia. Therefore, decolonization of MDROs in the gut by restoring colonization resistance through fecal microbiota transplantation (FMT) could be an effective infection control strategy for MDROs. Methods From March 2019 to November 2022, FMT for CPE and VRE decolonization in the gut was conducted at Hallym University Chuncheon Sacred Heart Hospital. Frozen or capsulized stool (MicroBiotix FMT Delivery Microbiota Preparation) from unrelated pre-screened healthy donor was used for each FMT. The rates of and the time to successful decolonization, defined as 3 consecutive negative results from rectal swab culture repeated with 3-day intervals after the initial FMT, were investigated in CPE and VRE rectal colonizers, respectively. Results FMT was performed in 60 CPE rectal carriers (KPC=55, KPC &amp; NDM=2, KPC &amp; IMP=1, NDM=1, NDM &amp; OXA=1) and in 15 VRE rectal carriers (E. faecium=14, E. faecalis=1). Among patients with follow-up data after initial FMT, decolonization success rates for CPE and VRE rectal carriers were 44.8% (26/58) and 66.7% (10/15) at 1 month, 77.1% (37/48) and 92.9% (13/14) at 3 months, 95.5% (42/44) and 100% (14/14) at 6 months, respectively. Median and mean times to decolonization after initial FMT were 30 and 43 days in CPE rectal colonizers and 14 and 29 days in VRE rectal colonizers, respectively. FMT results for decolonization of MDROs in the gut of Chuncheon Sacred Heart Hospital (ClinicalTrials.gov number, NCT04583098) Conclusion FMT as a microbiome restoration therapy is an effective method to control CPE and VRE colonization (ClinicalTrials.gov number, NCT04583098). Disclosures All Authors: No reported disclosures

2156. The Rational Design of SER-147: a Cultivated Microbial Consortium to Restore Colonization Resistance and Mitigate Infection in Chronic Liver Disease

Abstract Background Chronic liver disease (CLD) is a major cause of morbidity and mortality, with high risk of infection as CLD progresses. Gut microbiome disruption, which worsens with CLD severity, causes loss of colonization resistance and impaired gastrointestinal (GI) barrier function, enabling pathogen translocation across the GI tract. We evaluated shotgun metagenomic data from 3 studies and 288 patients with CLD to evaluate the role of the microbiome in the progression of disease, and enable the rational design of SER-147, a cultivated consortium of human commensal bacteria, to restore colonization resistance against key pathogens and promote GI homeostasis in CLD patients. Methods SER-147 design relied on both (1) microbiome targets identified from a bioinformatic analysis of public observational datasets in CLD patients and (2) past Seres clinical trial pharmacology data. We ingested genomic and matching clinical data from 3 studies and 288 patients (Table 1), processing all primary read data through Seres genomic databases to enable comparison with internal healthy comparator cohorts. Functional characterization of the Seres strain library (SSL) facilitated SER-147 design to include traits important to colonization resistance and GI barrier integrity (Figure 1).Table 1:Public observational studies of patients with CLD used to evaluate the role of the microbiome in CLD progression.Figure 1.Reverse Translational Design Pipeline for SER-147 Candidate Consortia. The design framework for preclinical drug candidates integrates a combination of public observational datasets in CLD patients, Seres interventional clinical trials, and proprietary bioinformatic algorithms to inform disease target identification. These data are subsequently fed into a rational design framework that utilizes (1) trial engraftment, (2) disease-informed preclinical microbiome modeling, and (3) functional learnings from SSL to identify taxa with the desired pharmacological properties. Results Bioinformatic analyses support evidence of progressive microbiome disruption and diversity loss as CLD worsens, as key Firmicutes are reduced while Proteobacteria are enriched. Rational design yielded candidate consortia with taxa that can (1) generate barrier-restorative metabolites (short-chain fatty acids, secondary bile acids, tryptophan metabolites), (2) reduce inflammatory cytokine production, (3) tolerate oxidative and acid stress, and (4) decolonize intestinal pathogens in preclinical models (Figure 2).Figure 2.Selection of strains by baseline characteristics for use in SER-147. Nineteen candidate bacterial strains were selected for inclusion in SER-147 candidate consortia based on numerous genotypic and phenotypic traits. Evidence of engraftment of strains in Seres clinical trials was a minimum inclusion criterion to help ensure pharmacokinetic capability of SER-147. Genomic and in silico design features included: depletion during CLD progression, predicted lantibiotic production, presence of KEGG-Orthologs for oxygen tolerance, and predicted contribution to decolonization phenotypes based on preclinical modeling. Phenotypic design features were selected based on extensive in vitro and in vivo characterization of strains and include the generation of barrier-restorative metabolites like short-chain fatty acids (SCFA), secondary bile acid conversion, and tryptophan metabolism. SER-147 candidate strains were additionally assessed in vitro for their capacity to tolerate low pH, grow in hypoxic culture conditions, suppress IL-8 activity, and utilize lactulose as a sole carbon source as it is a commonly prescribed medication in the CLD patient population Conclusion Patients with CLD are at increased risk of mortality from infections seeded from the GI tract due to microbiome disruption and GI barrier compromise. Microbiome therapeutics such as SER-147 represent a potentially powerful and novel approach to reducing the risk of infection in CLD by directly targeting key risk factors of GI-seeded infections. Disclosures Jenna Wurster, PhD, Seres Therapeutics: Paid Employee|Seres Therapeutics: Stocks/Bonds Tim Straub, MS, Seres Therapeutics: Employee|Seres Therapeutics: Stocks/Bonds Edward J. O'Brien, PhD, Seres Therapeutics: Employee|Seres Therapeutics: Stocks/Bonds Nathaniel J. Ennis, n/a, Seres Therapeutics: Employee|Seres Therapeutics: Stocks/Bonds Melissa Mayol, n/a, Seres Therapeutics: Employee|Seres Therapeutics: Stocks/Bonds Jessica Brown, n/a, Seres Therapeutics: Employee|Seres Therapeutics: Stocks/Bonds Marin Vulić, PhD, Seres Therapeutics: Employee|Seres Therapeutics: Stocks/Bonds Nicholas Beauchemin, n/a, Seres Therapeutics: Employee|Seres Therapeutics: Stocks/Bonds Elizabeth Halvorsen, PhD, Seres Therapeutics: Employee|Seres Therapeutics: Stocks/Bonds Christopher Ford, PhD, Seres Therapeutics: Employee|Seres Therapeutics: Stocks/Bonds Matthew Henn, PhD, Seres Therapeutics: Employee|Seres Therapeutics: Stocks/Bonds