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Huang Y, Cao J, Zhu M, Wang Z, Jin Z, Xiong Z. Nontoxigenic Bacteroides fragilis: A double-edged sword. Microbiol Res 2024; 286:127796. [PMID: 38870618 DOI: 10.1016/j.micres.2024.127796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2023] [Revised: 04/12/2024] [Accepted: 05/31/2024] [Indexed: 06/15/2024]
Abstract
The contribution of commensal microbes to human health and disease is unknown. Bacteroides fragilis (B. fragilis) is an opportunistic pathogen and a common colonizer of the human gut. Nontoxigenic B. fragilis (NTBF) and enterotoxigenic B. fragilis (ETBF) are two kinds of B. fragilis. NTBF has been shown to affect the host immune system and interact with gut microbes and pathogenic microbes. Previous studies indicated that certain strains of B. fragilis have the potential to serve as probiotics, based on their observed relationship with the immune system. However, several recent studies have shown detrimental effects on the host when beneficial gut bacteria are found in the digestive system or elsewhere. In some pathological conditions, NTBF may have adverse reactions. This paper presents a comprehensive analysis of NTBF ecology from the host-microbe perspective, encompassing molecular disease mechanisms analysis, bacteria-bacteria interaction, bacteria-host interaction, and the intricate ecological context of the gut. Our review provides much-needed insights into the precise application of NTBF.
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Affiliation(s)
- Yumei Huang
- Department of Gastroenterology, Liyuan Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Jiali Cao
- Department of Gastroenterology, Liyuan Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Mengpei Zhu
- Department of Gastroenterology, Liyuan Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Ziwen Wang
- Department of Gastroenterology, Liyuan Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Ze Jin
- Department of Gastroenterology, Liyuan Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Zhifan Xiong
- Department of Gastroenterology, Liyuan Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
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2
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Nilson R, Penumutchu S, Pagano FS, Belenky P. Metabolic changes associated with polysaccharide utilization reduce susceptibility to some β-lactams in Bacteroides thetaiotaomicron. mSphere 2024; 9:e0010324. [PMID: 39109911 DOI: 10.1128/msphere.00103-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2024] [Accepted: 07/07/2024] [Indexed: 08/29/2024] Open
Abstract
Antibiotic therapy alters bacterial abundance and metabolism in the gut microbiome, leading to dysbiosis and opportunistic infections. Bacteroides thetaiotaomicron (Bth) is both a commensal in the gut and an opportunistic pathogen in other body sites. Past work has shown that Bth responds to β-lactam treatment differently depending on the metabolic environment both in vitro and in vivo. Studies of other bacteria show that an increase in respiratory metabolism independent of growth rate promotes susceptibility to bactericidal antibiotics. We propose that Bth enters a protected state linked to an increase in polysaccharide utilization and a decrease in the use of simple sugars. Here, we apply antibiotic susceptibility testing, transcriptomic analysis, and genetic manipulation to characterize this polysaccharide-mediated tolerance (PM tolerance) phenotype. We found that a variety of mono- and disaccharides increased the susceptibility of Bth to several different β-lactams compared to polysaccharides. Transcriptomics indicated a metabolic shift from reductive to oxidative branches of the tricarboxylic acid cycle on polysaccharides. Accordingly, supplementation with intermediates of central carbon metabolism had varying effects on PM tolerance. Transcriptional analysis also showed a decrease in the expression of the electron transport chain (ETC) protein NQR and an increase in the ETC protein NUO, when given fiber versus glucose. Deletion of NQR increased Bth susceptibility while deletion of NUO and a third ETC protein NDH2 had no effect. This work confirms that carbon source utilization modulates antibiotic susceptibility in Bth and that anaerobic respiratory metabolism and the ETC play an essential role.IMPORTANCEAntibiotics are indispensable medications that revolutionized modern medicine. However, their effectiveness is challenged by a large array of resistance and tolerance mechanisms. Treatment with antibiotics also disrupts the gut microbiome which can adversely affect health. Bacteroides are prevalent in the gut microbiome and yet are frequently involved in anaerobic infections. Thus, understanding how antibiotics affect these bacteria is necessary to implement proper treatment. Recent work has investigated the role of metabolism in antibiotic susceptibility in distantly related bacteria such as Escherichia coli. Using antibiotic susceptibility testing, transcriptomics, and genetic manipulation, we demonstrate that polysaccharides reduce β-lactam susceptibility when compared to monosaccharides. This finding underscores the profound impact of metabolic adaptation on the therapeutic efficacy of antibiotics. In the long term, this work indicates that modulation of metabolism could make Bacteroides more susceptible during infections or protect them in the context of the microbiome.
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Affiliation(s)
- Rachael Nilson
- Department of Molecular Microbiology and Immunology, Brown University, Providence, Rhode Island, USA
| | - Swathi Penumutchu
- Department of Molecular Microbiology and Immunology, Brown University, Providence, Rhode Island, USA
| | - Francesco S Pagano
- Department of Molecular Microbiology and Immunology, Brown University, Providence, Rhode Island, USA
| | - Peter Belenky
- Department of Molecular Microbiology and Immunology, Brown University, Providence, Rhode Island, USA
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3
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Boyanova L, Boyanova L, Hadzhiyski P, Gergova R, Markovska R. Oxygen tolerance in anaerobes as a virulence factor and a health-beneficial property. Anaerobe 2024; 89:102897. [PMID: 39154706 DOI: 10.1016/j.anaerobe.2024.102897] [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: 06/02/2024] [Revised: 07/28/2024] [Accepted: 08/06/2024] [Indexed: 08/20/2024]
Abstract
Oxygen tolerance of anaerobes is a virulence factor, but can also be a beneficial property. Many species have evolved to tolerate or take advantage of the presence of low, especially nanaerobic (≤0.14 %) oxygen concentrations. Oxygen tolerance is genus-, species- and strain-dependent according to their protective mechanisms. It was better expressed in some pathogenic species such as Bacteroides fragilis, Clostridioides difficile, and Clostridium perfringens, as well as in Akkermansia muciniphila than in other potential probiotics such as Alistipes, Blautia and Roseburia spp. Different degrees of oxygen sensitivity were found between the strains of Anaerostipes, Faecalibacterium, and Bifidobacterium spp. Importantly, clostridial spores and anaerobes in biofilms are protected from oxidation. Rubrerythrins and flavodiiron proteins and two regulators (sigma factor B and PerR) contribute to C. difficile protection from reactive oxygen species (ROS). The frequent pathogen, B. fragilis, has numerous protective factors such as enzymes (catalase, superoxide dismutase, alkyl hydroperoxidase, thioredoxin peroxidase, and aerobic-type NrdAB ribonucleotide reductase), and nanaerobic respiration. Seven proteins confer strain-specific oxygen adaptation of Faecalibacterium prausnitzii. Oxygen tolerance protects anaerobes from ROS, shields their DNA and modulates gene expression. Furthermore, oxygen can induce mutations leading to antibiotic resistance as shown in Prevotella melaninogenica. Some Faecalibacterium, Anaerostipes, Bifidobacterium, and Akkermansia strains from the intestinal microbiota exhibiting oxygen tolerance may become next-generation probiotic candidates. Further studies are needed to reveal oxygen effects on more anaerobic species and strains, and the influence of oxygen on antibiotic resistance. More studies on oxygen-tolerant probiotic strains can be useful to optimize biotechnological methods.
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Affiliation(s)
- Lyudmila Boyanova
- Department of Medical Microbiology, Medical University of Sofia, 2 Zdrave Str., 1431, Sofia, Bulgaria.
| | - Liliya Boyanova
- Department of Medical Microbiology, Medical University of Sofia, 2 Zdrave Str., 1431, Sofia, Bulgaria
| | - Petyo Hadzhiyski
- Specialized Hospital for Active Pediatric Treatment, Medical University of Sofia, "Acad. Ivan Evstatiev Geshov" Blvd, 1606, Sofia, Bulgaria
| | - Raina Gergova
- Department of Medical Microbiology, Medical University of Sofia, 2 Zdrave Str., 1431, Sofia, Bulgaria
| | - Rumyana Markovska
- Department of Medical Microbiology, Medical University of Sofia, 2 Zdrave Str., 1431, Sofia, Bulgaria
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Gough AM, Parker AC, O'Bryan PJ, Whitehead TR, Roy S, Garcia BL, Hoffman PS, Jeffrey Smith C, Rocha ER. New functions of pirin proteins and a 2-ketoglutarate: Ferredoxin oxidoreductase ortholog in Bacteroides fragilis metabolism and their impact on antimicrobial susceptibility to metronidazole and amixicile. Microbiologyopen 2024; 13:e1429. [PMID: 39109824 PMCID: PMC11304471 DOI: 10.1002/mbo3.1429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 07/05/2024] [Accepted: 07/12/2024] [Indexed: 08/10/2024] Open
Abstract
The understanding of how central metabolism and fermentation pathways regulate antimicrobial susceptibility in the anaerobic pathogen Bacteroides fragilis is still incomplete. Our study reveals that B. fragilis encodes two iron-dependent, redox-sensitive regulatory pirin protein genes, pir1 and pir2. The mRNA expression of these genes increases when exposed to oxygen and during growth in iron-limiting conditions. These proteins, Pir1 and Pir2, influence the production of short-chain fatty acids and modify the susceptibility to metronidazole and amixicile, a new inhibitor of pyruvate: ferredoxin oxidoreductase in anaerobes. We have demonstrated that Pir1 and Pir2 interact directly with this oxidoreductase, as confirmed by two-hybrid system assays. Furthermore, structural analysis using AlphaFold2 predicts that Pir1 and Pir2 interact stably with several central metabolism enzymes, including the 2-ketoglutarate:ferredoxin oxidoreductases Kor1AB and Kor2CDAEBG. We used a series of metabolic mutants and electron transport chain inhibitors to demonstrate the extensive impact of bacterial metabolism on metronidazole and amixicile susceptibility. We also show that amixicile is an effective antimicrobial against B. fragilis in an experimental model of intra-abdominal infection. Our investigation led to the discovery that the kor2AEBG genes are essential for growth and have dual functions, including the formation of 2-ketoglutarate via the reverse TCA cycle. However, the metabolic activity that bypasses the function of Kor2AEBG following the addition of phospholipids or fatty acids remains undefined. Overall, our study provides new insights into the central metabolism of B. fragilis and its regulation by pirin proteins, which could be exploited for the development of new narrow-spectrum antimicrobials in the future.
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Affiliation(s)
- Andrea M. Gough
- Department of Microbiology and ImmunologyBrody School of Medicine at East Carolina UniversityGreenvilleNorth CarolinaUSA
| | - Anita C. Parker
- Department of Microbiology and ImmunologyBrody School of Medicine at East Carolina UniversityGreenvilleNorth CarolinaUSA
| | | | | | - Sourav Roy
- Department of Microbiology and ImmunologyBrody School of Medicine at East Carolina UniversityGreenvilleNorth CarolinaUSA
| | - Brandon L. Garcia
- Department of Microbiology and ImmunologyBrody School of Medicine at East Carolina UniversityGreenvilleNorth CarolinaUSA
| | - Paul S. Hoffman
- Department of Medicine, Division of Infectious Diseases and International HealthUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - C. Jeffrey Smith
- Department of Microbiology and ImmunologyBrody School of Medicine at East Carolina UniversityGreenvilleNorth CarolinaUSA
| | - Edson R. Rocha
- Department of Microbiology and ImmunologyBrody School of Medicine at East Carolina UniversityGreenvilleNorth CarolinaUSA
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Bhattacharya S, Sangave PC, Belemkar S, Anjum MM. pH-Sensitive Nanoparticles of Epigallocatechin-3-Gallate in Enhanced Colorectal Cancer Therapy. Nanomedicine (Lond) 2024; 19:459-481. [PMID: 38223987 DOI: 10.2217/nnm-2023-0342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 12/19/2023] [Indexed: 01/16/2024] Open
Abstract
AIM Encapsulating epigallocatechin-3-gallate (EGCG) in pH-sensitive polymeric nanoparticles for targeted delivery of drugs could revolutionize colorectal cancer treatment. MATERIALS & METHODS Nanoparticles were synthesized to release drugs at colon pH. Dynamic light scattering measured their average diameter and ζ-potential, while differential scanning calorimetry and x-ray diffraction assessed EGCG encapsulation. RESULTS The nanoparticles showed stability and bioavailability in the gastrointestinal tract, efficiently encapsulating and releasing over 93% of EGCG at pH 7.2. They enhanced cytotoxicity against HT-29 cells and demonstrated antibacterial properties, increasing apoptosis and cell cycle arrest. CONCLUSION The study underscores the potential of nanoparticles in enhancing EGCG delivery for colorectal cancer therapy, aiming to minimize side effects and improve therapeutic outcomes.
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Affiliation(s)
- Sankha Bhattacharya
- Department of Pharmaceutics, School of Pharmacy & Technology Management, SVKM'S NMIMS Deemed-to-be University, Shirpur, Maharashtra, 425405, India
| | - Preeti Chidambar Sangave
- Department of Pharmaceutics, School of Pharmacy & Technology Management, SVKM'S NMIMS Deemed-to-be University, Shirpur, Maharashtra, 425405, India
| | - Sateesh Belemkar
- Department of Pharmacology, Shobhaben Pratapbhai Patel School of Pharmacy & Technology Management, SVKM'S NMIMS Deemed-to-be University, Vile Parle (W), Mumbai, 400056, Maharashtra, India
| | - Md Meraj Anjum
- Department of Pharmaceutical Sciences, Babasaheb Bhimrao Ambedkar University, Lucknow, UP, 226025, India
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Little AS, Younker IT, Schechter MS, Bernardino PN, Méheust R, Stemczynski J, Scorza K, Mullowney MW, Sharan D, Waligurski E, Smith R, Ramanswamy R, Leiter W, Moran D, McMillin M, Odenwald MA, Iavarone AT, Sidebottom AM, Sundararajan A, Pamer EG, Eren AM, Light SH. Dietary- and host-derived metabolites are used by diverse gut bacteria for anaerobic respiration. Nat Microbiol 2024; 9:55-69. [PMID: 38177297 PMCID: PMC11055453 DOI: 10.1038/s41564-023-01560-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 11/14/2023] [Indexed: 01/06/2024]
Abstract
Respiratory reductases enable microorganisms to use molecules present in anaerobic ecosystems as energy-generating respiratory electron acceptors. Here we identify three taxonomically distinct families of human gut bacteria (Burkholderiaceae, Eggerthellaceae and Erysipelotrichaceae) that encode large arsenals of tens to hundreds of respiratory-like reductases per genome. Screening species from each family (Sutterella wadsworthensis, Eggerthella lenta and Holdemania filiformis), we discover 22 metabolites used as respiratory electron acceptors in a species-specific manner. Identified reactions transform multiple classes of dietary- and host-derived metabolites, including bioactive molecules resveratrol and itaconate. Products of identified respiratory metabolisms highlight poorly characterized compounds, such as the itaconate-derived 2-methylsuccinate. Reductase substrate profiling defines enzyme-substrate pairs and reveals a complex picture of reductase evolution, providing evidence that reductases with specificities for related cinnamate substrates independently emerged at least four times. These studies thus establish an exceptionally versatile form of anaerobic respiration that directly links microbial energy metabolism to the gut metabolome.
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Affiliation(s)
- Alexander S Little
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA
- Department of Microbiology, University of Chicago, Chicago, IL, USA
| | - Isaac T Younker
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA
- Department of Microbiology, University of Chicago, Chicago, IL, USA
| | - Matthew S Schechter
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA
- Department of Microbiology, University of Chicago, Chicago, IL, USA
| | - Paola Nol Bernardino
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA
- Department of Microbiology, University of Chicago, Chicago, IL, USA
| | - Raphaël Méheust
- Génomique Métabolique, CEA, Genoscope, Institut François Jacob, Université d'Évry, Université Paris-Saclay, CNRS, Evry, France
| | - Joshua Stemczynski
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA
- Department of Microbiology, University of Chicago, Chicago, IL, USA
| | - Kaylie Scorza
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA
- Department of Microbiology, University of Chicago, Chicago, IL, USA
| | | | - Deepti Sharan
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA
- Department of Microbiology, University of Chicago, Chicago, IL, USA
| | - Emily Waligurski
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA
| | - Rita Smith
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA
| | | | - William Leiter
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA
| | - David Moran
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA
| | - Mary McMillin
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA
| | - Matthew A Odenwald
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA
- Section of Gastroenterology, Hepatology, and Nutrition, Department of Medicine, University of Chicago, Chicago, IL, USA
| | - Anthony T Iavarone
- QB3/Chemistry Mass Spectrometry Facility, University of California, Berkeley, Berkeley, CA, USA
| | | | | | - Eric G Pamer
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA
- Department of Microbiology, University of Chicago, Chicago, IL, USA
- Section of Infectious Diseases & Global Health, Department of Medicine, University of Chicago, Chicago, IL, USA
| | - A Murat Eren
- Helmholtz Institute for Functional Marine Biodiversity, Oldenburg, Germany
- Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg, Oldenbug, Germany
| | - Samuel H Light
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA.
- Department of Microbiology, University of Chicago, Chicago, IL, USA.
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Abbondio M, Tanca A, De Diego L, Sau R, Bibbò S, Pes GM, Dore MP, Uzzau S. Metaproteomic assessment of gut microbial and host functional perturbations in Helicobacter pylori-infected patients subjected to an antimicrobial protocol. Gut Microbes 2023; 15:2291170. [PMID: 38063474 PMCID: PMC10730194 DOI: 10.1080/19490976.2023.2291170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 11/30/2023] [Indexed: 12/18/2023] Open
Abstract
The impact of therapeutic interventions on the human gut microbiota (GM) is a clinical issue of paramount interest given the strong interconnection between microbial dynamics and human health. Orally administered antibiotics are known to reduce GM biomass and modify GM taxonomic profile. However, the impact of antimicrobial therapies on GM functions and biochemical pathways has scarcely been studied. Here, we characterized the fecal metaproteome of 10 Helicobacter pylori-infected patients before (T0) and after 10 days (T1) of a successful quadruple therapy (bismuth, tetracycline, metronidazole, and rabeprazole) and 30 days after therapy cessation (T2), to investigate how GM and host functions change during the eradication and healing processes. At T1, the abundance ratio between microbial and host proteins was reversed compared with that at T0 and T2. Several pathobionts (including Klebsiella, Proteus, Enterococcus, Muribaculum, and Enterocloster) were increased at T1. Therapy reshaped the relative contributions of the functions required to produce acetate, propionate, and butyrate. Proteins related to the uptake and processing of complex glycans were increased. Microbial cross-feeding with sialic acid, fucose, and rhamnose was enhanced, whereas hydrogen sulfide production was reduced. Finally, microbial proteins involved in antibiotic resistance and inflammation were more abundant after therapy. Moreover, a reduction in host proteins with known roles in inflammation and H. pylori-mediated carcinogenesis was observed. In conclusion, our results support the use of metaproteomics to monitor drug-induced remodeling of GM and host functions, opening the way for investigating new antimicrobial therapies aimed at preserving gut environmental homeostasis.
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Affiliation(s)
- Marcello Abbondio
- Department of Biomedical Sciences, University of Sassari, Sassari, Italy
| | - Alessandro Tanca
- Department of Biomedical Sciences, University of Sassari, Sassari, Italy
| | - Laura De Diego
- Department of Biomedical Sciences, University of Sassari, Sassari, Italy
| | - Rosangela Sau
- Department of Biomedical Sciences, University of Sassari, Sassari, Italy
| | - Stefano Bibbò
- Department of Medicine, Surgery and Pharmacy, University of Sassari, Sassari, Italy
| | - Giovanni Mario Pes
- Department of Medicine, Surgery and Pharmacy, University of Sassari, Sassari, Italy
| | - Maria Pina Dore
- Department of Medicine, Surgery and Pharmacy, University of Sassari, Sassari, Italy
| | - Sergio Uzzau
- Department of Biomedical Sciences, University of Sassari, Sassari, Italy
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Paunkov A, Hummel K, Strasser D, Sóki J, Leitsch D. Proteomic analysis of metronidazole resistance in the human facultative pathogen Bacteroides fragilis. Front Microbiol 2023; 14:1158086. [PMID: 37065137 PMCID: PMC10102347 DOI: 10.3389/fmicb.2023.1158086] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 03/14/2023] [Indexed: 04/03/2023] Open
Abstract
The anaerobic gut bacteria and opportunistic pathogen Bacteroides fragilis can cause life-threatening infections when leaving its niche and reaching body sites outside of the gut. The antimicrobial metronidazole is a mainstay in the treatment of anaerobic infections and also highly effective against Bacteroides spp. Although resistance rates have remained low in general, metronidazole resistance does occur in B. fragilis and can favor fatal disease outcomes. Most metronidazole-resistant Bacteroides isolates harbor nim genes, commonly believed to encode for nitroreductases which deactivate metronidazole. Recent research, however, suggests that the mode of resistance mediated by Nim proteins might be more complex than anticipated because they affect the cellular metabolism, e.g., by increasing the activity of pyruvate:ferredoxin oxidoreductase (PFOR). Moreover, although nim genes confer only low-level metronidazole resistance to Bacteroides, high-level resistance can be much easier induced in the laboratory in the presence of a nim gene than without. Due to these observations, we hypothesized that nim genes might induce changes in the B. fragilis proteome and performed comparative mass-spectrometric analyses with B. fragilis 638R, either with or without the nimA gene. Further, we compared protein expression profiles in both strains after induction of high-level metronidazole resistance. Interestingly, only few proteins were repeatedly found to be differentially expressed in strain 638R with the nimA gene, one of them being the flavodiiron protein FprA, an enzyme involved in oxygen scavenging. After induction of metronidazole resistance, a far higher number of proteins were found to be differentially expressed in 638R without nimA than in 638R with nimA. In the former, factors for the import of hemin were strongly downregulated, indicating impaired iron import, whereas in the latter, the observed changes were not only less numerous but also less specific. Both resistant strains, however, displayed a reduced capability of scavenging oxygen. Susceptibility to metronidazole could be widely restored in resistant 638R without nimA by supplementing growth media with ferrous iron sulfate, but not so in resistant 638R with the nimA gene. Finally, based on the results of this study, we present a novel hypothetic model of metronidazole resistance and NimA function.
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Affiliation(s)
- Ana Paunkov
- Institute for Specific Prophylaxis and Tropical Medicine, Center for Pathophysiology, Infectiology, and Immunology, Medical University of Vienna, Vienna, Austria
| | - Karin Hummel
- VetCore Facility for Research, University of Veterinary Medicine, Vienna, Austria
| | - Doris Strasser
- Institute for Specific Prophylaxis and Tropical Medicine, Center for Pathophysiology, Infectiology, and Immunology, Medical University of Vienna, Vienna, Austria
| | - József Sóki
- Faculty of Medicine, Institute of Medical Microbiology, University of Szeged, Szeged, Hungary
| | - David Leitsch
- Institute for Specific Prophylaxis and Tropical Medicine, Center for Pathophysiology, Infectiology, and Immunology, Medical University of Vienna, Vienna, Austria
- *Correspondence: David Leitsch,
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