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Fitzpatrick F, Brennan R, van Prehn J, Skally M, Brady M, Burns K, Rooney C, Wilcox MH. European Practice for CDI Treatment. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 1435:57-84. [PMID: 38175471 DOI: 10.1007/978-3-031-42108-2_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Clostridioides difficile infection (CDI) remains a significant cause of morbidity and mortality worldwide. Historically, two antibiotics (metronidazole and vancomycin) and a recent third (fidaxomicin) have been used for CDI treatment; convincing data are now available showing that metronidazole is the least efficacious agent. The European Society of Clinical Microbiology and Infectious Diseases (ESCMID) management guidance for CDI were updated in 2021. This guidance document outlines the treatment options for a variety of CDI clinical scenarios and for non-antimicrobial management (e.g., faecal microbiota transplantation, FMT). One of the main changes is that metronidazole is no longer recommended as first-line CDI treatment. Rather, fidaxomicin is preferred on the basis of reduced recurrence rates with vancomycin as an acceptable alternative. Recommended options for recurrent CDI now include bezlotoxumab as well as FMT.A 2017 survey of 20 European countries highlighted variation internationally in CDI management strategies. A variety of restrictions were in place in 65% countries prior to use of new anti-CDI treatments, including committee/infection specialist approval or economic review/restrictions. This survey was repeated in November 2022 to assess the current landscape of CDI management practices in Europe. Of 64 respondents from 17 countries, national CDI guidelines existed in 14 countries, and 11 have already/plan to incorporate the ESCMID 2021 CDI guidance, though implementation has not been surveyed in 6. Vancomycin is the most commonly used first-line agent for the treatment of CDI (n = 42, 66%), followed by fidaxomicin (n = 30, 47%). Six (9%) respondents use metronidazole as first-line agent for CDI treatment, whereas 22 (34%) only in selected low-risk patient groups. Fidaxomicin is more likely to be used in high-risk patient groups. Availability of anti-CDI therapy influenced prescribing in six respondents (9%). Approval pre-prescription was required before vancomycin (n = 3, 5%), fidaxomicin (n = 10, 6%), bezlotoxumab (n = 11, 17%) and FMT (n = 10, 6%). Implementation of CDI guidelines is rarely audited.Novel anti-CDI agents are being evaluated; it is not yet clear what will be the roles of these agents. The treatment of recurrent CDI is particularly troublesome, and several different live biotherapeutics are being developed, in addition to FMT.
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Affiliation(s)
- Fidelma Fitzpatrick
- Department of Clinical Microbiology, The Royal College of Surgeons in Ireland, Dublin, Ireland.
- Department of Clinical Microbiology, Beaumont Hospital, Dublin, Ireland.
| | - Robert Brennan
- Department of Clinical Microbiology, The Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Joffrey van Prehn
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Mairead Skally
- Department of Clinical Microbiology, The Royal College of Surgeons in Ireland, Dublin, Ireland
- Department of Clinical Microbiology, Beaumont Hospital, Dublin, Ireland
| | - Melissa Brady
- Health Protection Surveillance Centre (HPSC), Dublin, Ireland
| | - Karen Burns
- Department of Clinical Microbiology, Beaumont Hospital, Dublin, Ireland
| | - Christopher Rooney
- Microbiology, Leeds Teaching Hospitals, Leeds, UK
- University of Leeds, Leeds, UK
| | - Mark H Wilcox
- University of Leeds, Leeds, UK.
- Leeds Teaching Hospitals and Leeds Regional Public Health Laboratory, UK Health Security Agency (UKHSA), Leeds, UK.
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Chromosomal Position of Ribosomal Protein Genes Affects Long-Term Evolution of Vibrio cholerae. mBio 2023; 14:e0343222. [PMID: 36861972 PMCID: PMC10127744 DOI: 10.1128/mbio.03432-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/03/2023] Open
Abstract
It is unclear how gene order within the chromosome influences genome evolution. Bacteria cluster transcription and translation genes close to the replication origin (oriC). In Vibrio cholerae, relocation of s10-spc-α locus (S10), the major locus of ribosomal protein genes, to ectopic genomic positions shows that its relative distance to the oriC correlates to a reduction in growth rate, fitness, and infectivity. To test the long-term impact of this trait, we evolved 12 populations of V. cholerae strains bearing S10 at an oriC-proximal or an oriC-distal location for 1,000 generations. During the first 250 generations, positive selection was the main force driving mutation. After 1,000 generations, we observed more nonadaptative mutations and hypermutator genotypes. Populations fixed inactivating mutations at many genes linked to virulence: flagellum, chemotaxis, biofilm, and quorum sensing. Throughout the experiment, all populations increased their growth rates. However, those bearing S10 close to oriC remained the fittest, indicating that suppressor mutations cannot compensate for the genomic position of the main ribosomal protein locus. Selection and sequencing of the fastest-growing clones allowed us to characterize mutations inactivating, among other sites, flagellum master regulators. Reintroduction of these mutations into the wild-type context led to a ≈10% growth improvement. In conclusion, the genomic location of ribosomal protein genes conditions the evolutionary trajectory of V. cholerae. While genomic content is highly plastic in prokaryotes, gene order is an underestimated factor that conditions cellular physiology and evolution. A lack of suppression enables artificial gene relocation as a tool for genetic circuit reprogramming. IMPORTANCE The bacterial chromosome harbors several entangled processes such as replication, transcription, DNA repair, and segregation. Replication begins bidirectionally at the replication origin (oriC) until the terminal region (ter) organizing the genome along the ori-ter axis gene order along this axis could link genome structure to cell physiology. Fast-growing bacteria cluster translation genes near oriC. In Vibrio cholerae, moving them away was feasible but at the cost of losing fitness and infectivity. Here, we evolved strains harboring ribosomal genes close or far from oriC. Growth rate differences persisted after 1,000 generations. No mutation was able to compensate for the growth defect, showing that ribosomal gene location conditions their evolutionary trajectory. Despite the high plasticity of bacterial genomes, evolution has sculpted gene order to optimize the ecological strategy of the microorganism. We observed growth rate improvement throughout the evolution experiment that occurred at expense of energetically costly processes such the flagellum biosynthesis and virulence-related functions. From the biotechnological point of view, manipulation of gene order enables altering bacterial growth with no escape events.
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Roseboom AM, Ducarmon QR, Hornung BVH, Harmanus C, Crobach MJT, Kuijper EJ, Vossen RHAM, Kloet SL, Smits WK. Carriage of three plasmids in a single human clinical isolate of Clostridioides difficile. Plasmid 2023; 125:102669. [PMID: 36572199 DOI: 10.1016/j.plasmid.2022.102669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2022] [Revised: 11/17/2022] [Accepted: 12/20/2022] [Indexed: 12/24/2022]
Abstract
A subset of clinical isolates of Clostridioides difficile contains one or more plasmids and these plasmids can harbor virulence and antimicrobial resistance determinants. Despite their potential importance, C. difficile plasmids remain poorly characterized. Here, we provide the complete genome sequence of a human clinical isolate that carries three high-copy number plasmids from three different plasmid families that are therefore compatible. For two of these, we identify a region capable of sustaining plasmid replication in C. difficile that is also compatible with the plasmid pCD630 that is found in many laboratory strains. Together, our data advance our understanding of C. difficile plasmid biology.
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Affiliation(s)
- Anna M Roseboom
- Department of Medical Microbiology and Leiden University Center of Infectious Diseases (LU-CID), Leiden University Medical Center, Leiden, the Netherlands.
| | - Quinten R Ducarmon
- Department of Medical Microbiology and Leiden University Center of Infectious Diseases (LU-CID), Leiden University Medical Center, Leiden, the Netherlands.
| | - Bastian V H Hornung
- Department of Medical Microbiology and Leiden University Center of Infectious Diseases (LU-CID), Leiden University Medical Center, Leiden, the Netherlands
| | - Céline Harmanus
- Department of Medical Microbiology and Leiden University Center of Infectious Diseases (LU-CID), Leiden University Medical Center, Leiden, the Netherlands.
| | - Monique J T Crobach
- Department of Medical Microbiology and Leiden University Center of Infectious Diseases (LU-CID), Leiden University Medical Center, Leiden, the Netherlands.
| | - Ed J Kuijper
- Department of Medical Microbiology and Leiden University Center of Infectious Diseases (LU-CID), Leiden University Medical Center, Leiden, the Netherlands.
| | - Rolf H A M Vossen
- Department of Human Genetics, Leiden Genome Technology Center, Leiden University Medical Center, Leiden, the Netherlands.
| | - Susan L Kloet
- Department of Human Genetics, Leiden Genome Technology Center, Leiden University Medical Center, Leiden, the Netherlands.
| | - Wiep Klaas Smits
- Department of Medical Microbiology and Leiden University Center of Infectious Diseases (LU-CID), Leiden University Medical Center, Leiden, the Netherlands; Centre for Microbial Cell Biology, Leiden, the Netherlands.
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4
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Garey KW, McPherson J, Dinh AQ, Hu C, Jo J, Wang W, Lancaster CK, Gonzales-Luna AJ, Loveall C, Begum K, Alam MJ, Silverman MH, Hanson B. Efficacy, Safety, Pharmacokinetics, and Microbiome Changes of Ibezapolstat in Adults with Clostridioides difficile Infection: A Phase 2a Multicenter Clinical Trial. Clin Infect Dis 2022; 75:1164-1170. [PMID: 35134880 PMCID: PMC9525077 DOI: 10.1093/cid/ciac096] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Indexed: 12/17/2022] Open
Abstract
Background This study was the first human validation of the gram-positive bacterial DNA polymerase IIIC target in patients with Clostridioides difficile infection. The primary objectives were to assess clinical cure rates and adverse events (AEs). Secondary objectives were to evaluate plasma/fecal pharmacokinetics, microbiologic eradication, microbiome and bile acid effects, and sustained clinical cure (SCC) with ibezapolstat. Methods This single-arm, open-label, phase 2a study enrolled adults with C. difficile infection at 4 US centers. Patients received ibezapolstat 450 mg orally every 12 hours for 10 days and followed for an additional 28 days to assess study objectives. Results Ten patients with a mean (standard deviation [SD]) age of 49 [15] years were enrolled. Seven AEs were reported classified as mild-moderate. Plasma levels of ibezapolstat ranged from 233 to 578 ng/mL while mean (SD) fecal levels were 416 (494) µg/g stool by treatment day 3 and >1000 µg/g stool by days 8–10. A rapid increase in alpha diversity in the fecal microbiome was noted after starting ibezapolstat therapy, which was maintained after completion of therapy. A proportional decrease in Bacteroidetes phylum was observed (mean change [SD], −10.0% [4.8%]; P = .04) with a concomitantly increased proportion of Firmicutes phylum (+14.7% [5.4%]; P = .009). Compared with baseline, total primary bile acids decreased by a mean (SD) of 40.1 (9.6) ng/mg stool during therapy (P < .001) and 40.5 (14.1) ng/mg stool after completion of therapy (P = .007). Rates of both initial clinical cure and SCC at 28 days were 100% (10 of 10 patients). Conclusions In this phase 2a study, 10 of 10 patients achieved SCC, demonstrated favorable pharmacokinetics, minimal AEs, and beneficial microbiome and bile acids results. These results support continued clinical development.
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Affiliation(s)
- Kevin W Garey
- University of Houston College of Pharmacy, Houston, TX USA.,University of Texas School of Public Health, Houston, TX USA
| | | | - An Q Dinh
- University of Texas School of Public Health, Houston, TX USA
| | - Chenlin Hu
- University of Houston College of Pharmacy, Houston, TX USA
| | - Jinhee Jo
- University of Houston College of Pharmacy, Houston, TX USA
| | - Weiqun Wang
- University of Houston College of Pharmacy, Houston, TX USA
| | | | | | | | | | | | | | - Blake Hanson
- University of Texas School of Public Health, Houston, TX USA
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5
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Oliveira Paiva AM, Friggen AH, Douwes R, Wittekoek B, Smits WK. Practical observations on the use of fluorescent reporter systems in Clostridioides difficile. Antonie van Leeuwenhoek 2022; 115:297-323. [PMID: 35039954 DOI: 10.1007/s10482-021-01691-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 11/19/2021] [Indexed: 12/18/2022]
Abstract
Fluorescence microscopy is a valuable tool to study a broad variety of bacterial cell components and dynamics thereof. For Clostridioides difficile, the fluorescent proteins CFPopt, mCherryOpt and phiLOV2.1, and the self-labelling tags SNAPCd and HaloTag, hereafter collectively referred as fluorescent systems, have been described to explore different cellular pathways. In this study, we sought to characterize previously used fluorescent systems in C. difficile cells. We performed single cell analyses using fluorescence microscopy of exponentially growing C. difficile cells harbouring different fluorescent systems, either expressing these separately in the cytosol or fused to the C-terminus of HupA, under defined conditions. We show that the intrinsic fluorescence of C. difficile cells increases during growth, independent of sigB or spo0A. However, when C. difficile cells are exposed to environmental oxygen autofluorescence is enhanced. Cytosolic overexpression of the different fluorescent systems alone, using the same expression signals, showed heterogeneous expression of the fluorescent systems. High levels of mCherryOpt were toxic for C. difficile cells limiting the applicability of this fluorophore as a transcriptional reporter. When fused to HupA, a C. difficile histone-like protein, the fluorescent systems behaved similarly and did not affect the HupA overproduction phenotype. The present study compares several commonly used fluorescent systems for application as transcriptional or translational reporters in microscopy and summarizes the limitations and key challenges for live-cell imaging of C. difficile. Due to independence of molecular oxygen and fluorescent signal, SNAPCd appears the most suitable candidate for live-cell imaging in C. difficile to date.
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Affiliation(s)
- Ana M Oliveira Paiva
- Department of Medical Microbiology, Section Experimental Bacteriology, Leiden University Medical Center, Leiden, The Netherlands.,Center for Microbial Cell Biology, Leiden, The Netherlands.,Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRS, 91198, Gif-sur-Yvette, France
| | - Annemieke H Friggen
- Department of Medical Microbiology, Section Experimental Bacteriology, Leiden University Medical Center, Leiden, The Netherlands.,Center for Microbial Cell Biology, Leiden, The Netherlands
| | - Roxanne Douwes
- Department of Medical Microbiology, Section Experimental Bacteriology, Leiden University Medical Center, Leiden, The Netherlands
| | - Bert Wittekoek
- Department of Medical Microbiology, Section Experimental Bacteriology, Leiden University Medical Center, Leiden, The Netherlands
| | - Wiep Klaas Smits
- Department of Medical Microbiology, Section Experimental Bacteriology, Leiden University Medical Center, Leiden, The Netherlands. .,Center for Microbial Cell Biology, Leiden, The Netherlands.
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6
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Garey KW, Begum K, Lancaster C, Gonzales-Luna A, Bui D, Mercier J, Seng Yue C, Ducharme MP, Hu M, Vince B, Silverman MH, Alam MJ, Kankam M. A randomized, double-blind, placebo-controlled, single and multiple ascending dose Phase 1 study to determine the safety, pharmacokinetics and food and faecal microbiome effects of ibezapolstat administered orally to healthy subjects. J Antimicrob Chemother 2021; 75:3635-3643. [PMID: 32892222 PMCID: PMC7662179 DOI: 10.1093/jac/dkaa364] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 07/17/2020] [Indexed: 01/07/2023] Open
Abstract
Background Clostridioides difficile infection is the most common cause of healthcare-associated infections in the USA, with limited treatment options. Ibezapolstat is a novel DNA polymerase IIIC inhibitor with in vitro activity against C. difficile. Objectives and methods Randomized, double-blind, placebo-controlled study to assess the safety, tolerability and pharmacokinetics of ibezapolstat in healthy volunteers. Microbiome changes associated with ibezapolstat were compared with vancomycin over a 10 day course using shotgun metagenomics. Results A total of 62 subjects aged 31 ± 7 years (45% female; average BMI: 25 ± 3 kg/m2) were randomized. Ibezapolstat was well tolerated with a safety signal similar to placebo. Ibezapolstat had minimal systemic absorption with the majority of plasma concentrations less than 1 µg/mL. In the multiday, ascending dose study, ibezapolstat concentrations of 2000 µg/g of stool were observed by Day 2 and for the remainder of the dosing time period. In the multiday, multiple-dose arm, baseline microbiota was comparable between subjects that received ibezapolstat compared with vancomycin. At Day 10 of dosing, differential abundance analysis and β-diversity demonstrated a distinct difference between the microbiome in subjects given vancomycin compared with either dose of ibezapolstat (P = 0.006). α-Diversity changes were characterized as an increase in the Actinobacteria phylum in subjects that received ibezapolstat and an increase in Proteobacteria in subjects given vancomycin. Conclusions Ibezapolstat was shown to be safe and well tolerated, with minimal systemic exposure, high stool concentrations and a distinct microbiome profile compared with oral vancomycin. These results support further clinical development of ibezapolstat for patients with C. difficile infection.
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Affiliation(s)
| | | | | | | | - Dinh Bui
- University of Houston, Houston, TX, USA
| | - Julie Mercier
- Altasciences Clinical Kansas, Overland Park, KS, USA
| | | | | | - Ming Hu
- University of Houston, Houston, TX, USA
| | - Bradley Vince
- Altasciences Clinical Kansas, Overland Park, KS, USA
| | | | | | - Martin Kankam
- Altasciences Clinical Kansas, Overland Park, KS, USA
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7
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Oliveira Paiva AM, van Eijk E, Friggen AH, Weigel C, Smits WK. Identification of the Unwinding Region in the Clostridioides difficile Chromosomal Origin of Replication. Front Microbiol 2020; 11:581401. [PMID: 33133049 PMCID: PMC7561715 DOI: 10.3389/fmicb.2020.581401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 08/31/2020] [Indexed: 12/14/2022] Open
Abstract
Faithful DNA replication is crucial for viability of cells across all kingdoms. Targeting DNA replication is a viable strategy for inhibition of bacterial pathogens. Clostridioides difficile is an important enteropathogen that causes potentially fatal intestinal inflammation. Knowledge about DNA replication in this organism is limited and no data is available on the very first steps of DNA replication. Here, we use a combination of in silico predictions and in vitro experiments to demonstrate that C. difficile employs a bipartite origin of replication that shows DnaA-dependent melting at oriC2, located in the dnaA-dnaN intergenic region. Analysis of putative origins of replication in different clostridia suggests that the main features of the origin architecture are conserved. This study is the first to characterize aspects of the origin region of C. difficile and contributes to our understanding of the initiation of DNA replication in clostridia.
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Affiliation(s)
- Ana M Oliveira Paiva
- Department of Medical Microbiology, Section Experimental Bacteriology, Leiden University Medical Center, Leiden, Netherlands.,Centre for Microbial Cell Biology, Leiden, Netherlands
| | - Erika van Eijk
- Department of Medical Microbiology, Section Experimental Bacteriology, Leiden University Medical Center, Leiden, Netherlands
| | - Annemieke H Friggen
- Department of Medical Microbiology, Section Experimental Bacteriology, Leiden University Medical Center, Leiden, Netherlands
| | - Christoph Weigel
- Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany
| | - Wiep Klaas Smits
- Department of Medical Microbiology, Section Experimental Bacteriology, Leiden University Medical Center, Leiden, Netherlands.,Centre for Microbial Cell Biology, Leiden, Netherlands
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8
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Kullar R, Tran MCN, Goldstein EJC. Investigational Treatment Agents for Recurrent Clostridioides difficile Infection (rCDI). J Exp Pharmacol 2020; 12:371-384. [PMID: 33116952 PMCID: PMC7553590 DOI: 10.2147/jep.s242959] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 08/13/2020] [Indexed: 11/23/2022] Open
Abstract
Clostridioides difficile infection (CDI) is a major cause of nosocomial diarrhea that is deemed a global health threat. C. difficile strain BI/NAP1/027 has contributed to the increase in the mortality, severity of CDI outbreaks and recurrence rates (rCDI). Updated CDI treatment guidelines suggest vancomycin and fidaxomicin as initial first-line therapies that have initial clinical cure rates of over 80%. Unacceptably high recurrence rates of 15–30% in patients for the first episode and 40% for the second recurrent episode are reported. Alternative treatments for rCDI include fecal microbiota transplant and a human monoclonal antibody, bezlotoxumab, that can be used in patients with high risk of rCDI. Various emerging potential therapies with narrow spectrum of activity and little systemic absorption that are in development include 1) Ibezapolstat (formerly ACX-362E), MGB-BP-3, and DS-2969b-targeting bacterial DNA replication, 2) CRS3213 (REP3123)-inhibiting toxin production and spore formation, 3) ramizol and ramoplanin-affecting bacterial cell wall, 4) LFF-571-blocking protein synthesis, 5) Alanyl-L-Glutamine (alanylglutamine)-inhibiting damage caused by C. difficile by protecting intestinal mucosa, and 6) DNV3837 (MCB3681)-prodrug consisting of an oxazolidinone–quinolone combination that converts to the active form DNV3681 that has activity in vitro against C. difficile. This review article provides an overview of these developing drugs that can have potential role in the treatment of rCDI and in lowering recurrence rates.
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Affiliation(s)
| | - Mai-Chi N Tran
- Pharmacy Department, Keck Medical Center of USC, Los Angeles, CA, USA.,Clinica Juan Pablo Medical Group, Los Angeles, CA, USA
| | - Ellie J C Goldstein
- R.M. Alden Research Laboratory, Santa Monica, CA, USA.,David Geffen School of Medicine, Los Angeles, CA, USA
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Redefining the Clostridioides difficile σ B Regulon: σ B Activates Genes Involved in Detoxifying Radicals That Can Result from the Exposure to Antimicrobials and Hydrogen Peroxide. mSphere 2020; 5:5/5/e00728-20. [PMID: 32938698 PMCID: PMC7494833 DOI: 10.1128/msphere.00728-20] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In many Gram-positive bacteria, the general stress response is regulated at the transcriptional level by the alternative sigma factor sigma B (σB). In C. difficile, σB has been implicated in protection against stressors such as reactive oxygen species (ROS) and antimicrobial compounds. Here, we used an anti-σB antibody to demonstrate time-limited overproduction of σB in C. difficile despite its toxicity at higher cellular concentrations. This toxicity eventually led to the loss of the plasmid used for anhydrotetracycline-induced σB gene expression. Inducible σB overproduction uncouples σB expression from its native regulatory network and allows for the refinement of the previously proposed σB regulon. At least 32% of the regulon was found to consist of genes involved in the response to reactive radicals. Direct gene activation by C. difficile σB was demonstrated through in vitro runoff transcription of specific target genes (cd0350, cd3614, cd3605, and cd2963). Finally, we demonstrated that different antimicrobials and hydrogen peroxide induce these genes in a manner dependent on this sigma factor, using a plate-based luciferase reporter assay. Together, our work suggests that lethal exposure to antimicrobials may result in the formation of toxic radicals that lead to σB-dependent gene activation.IMPORTANCE Sigma B is the alternative sigma factor governing stress response in many Gram-positive bacteria. In C. difficile, a sigB mutant shows pleiotropic transcriptional effects. Here, we determine genes that are likely direct targets of σB by evaluating the transcriptional effects of σB overproduction, provide biochemical evidence of direct transcriptional activation by σB, and show that σB-dependent genes can be activated by antimicrobials. Together, our data suggest that σB is a key player in dealing with toxic radicals.
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10
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The σBsignalling activation pathway in the enteropathogenClostridioides difficile. Environ Microbiol 2019; 21:2852-2870. [DOI: 10.1111/1462-2920.14642] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 04/16/2019] [Accepted: 04/24/2019] [Indexed: 01/05/2023]
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