1
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Moussa AY. Endophytes: a uniquely tailored source of potential antibiotic adjuvants. Arch Microbiol 2024; 206:207. [PMID: 38581477 PMCID: PMC10998792 DOI: 10.1007/s00203-024-03891-y] [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: 12/25/2023] [Revised: 02/06/2024] [Accepted: 02/08/2024] [Indexed: 04/08/2024]
Abstract
Multidrug microbial resistance is risking an annual loss of more than 10 million people' lives by 2050. Solutions include the rational use of antibiotics and the use of drugs that reduce resistance or completely obliterate them. Here endophytes come to play due to their high-yield production and inherent nature to produce antimicrobial molecules. Around 40%, 45% and 17% of antibacterial agents were obtained from fungi, actinomycetes, and bacteria, respectively, whose secondary metabolites revealed effectiveness against resistant microbes such as MRSA, MRSE, and Shigella flexneri. Endophyte's role was not confined to bactericidal effect but extended to other mechanisms against MDR microbes, among which was the adjuvant role or the "magic bullets". Scarce focus was given to antibiotic adjuvants, and many laboratories today just screen for the antimicrobial activity without considering combinations with traditional antibiotics, which means real loss of promising resistance combating molecules. While some examples of synthetic adjuvants were introduced in the last decade, the number is still far from covering the disused antibiotics and restoring them back to clinical use. The data compiled in this article demonstrated the significance of quorum sensing as a foreseen mechanism for adjuvants from endophytes secondary metabolites, which call for urgent in-depth studies of their molecular mechanisms. This review, comprehensively and for the first time, sheds light on the significance of endophytes secondary metabolites in solving AMR problem as AB adjuvants.
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Affiliation(s)
- Ashaimaa Y Moussa
- Department of Pharmacognosy, Faculty of Pharmacy, Ain-Shams University, African Union Organization Street, Abbassia, Cairo, 11566, Egypt.
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2
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Jeremia L, Deprez BE, Dey D, Conn GL, Wuest WM. Ribosome-targeting antibiotics and resistance via ribosomal RNA methylation. RSC Med Chem 2023; 14:624-643. [PMID: 37122541 PMCID: PMC10131624 DOI: 10.1039/d2md00459c] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 02/17/2023] [Indexed: 03/05/2023] Open
Abstract
The rise of multidrug-resistant bacterial infections is a cause of global concern. There is an urgent need to both revitalize antibacterial agents that are ineffective due to resistance while concurrently developing new antibiotics with novel targets and mechanisms of action. Pathogen associated resistance-conferring ribosomal RNA (rRNA) methyltransferases are a growing threat that, as a group, collectively render a total of seven clinically-relevant ribosome-targeting antibiotic classes ineffective. Increasing frequency of identification and their growing prevalence relative to other resistance mechanisms suggests that these resistance determinants are rapidly spreading among human pathogens and could contribute significantly to the increased likelihood of a post-antibiotic era. Herein, with a view toward stimulating future studies to counter the effects of these rRNA methyltransferases, we summarize their prevalence, the fitness cost(s) to bacteria of their acquisition and expression, and current efforts toward targeting clinically relevant enzymes of this class.
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Affiliation(s)
- Learnmore Jeremia
- Department of Chemistry, Emory University 1515 Dickey Dr. Atlanta GA 30322 USA
| | - Benjamin E Deprez
- Department of Chemistry, Emory University 1515 Dickey Dr. Atlanta GA 30322 USA
| | - Debayan Dey
- Department of Biochemistry, Emory University School of Medicine 1510 Clifton Rd. Atlanta GA 30322 USA
| | - Graeme L Conn
- Department of Biochemistry, Emory University School of Medicine 1510 Clifton Rd. Atlanta GA 30322 USA
- Emory Antibiotic Resistance Center, Emory University School of Medicine 1510 Clifton Rd. Atlanta GA 30322 USA
| | - William M Wuest
- Department of Chemistry, Emory University 1515 Dickey Dr. Atlanta GA 30322 USA
- Emory Antibiotic Resistance Center, Emory University School of Medicine 1510 Clifton Rd. Atlanta GA 30322 USA
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3
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Dhanda G, Acharya Y, Haldar J. Antibiotic Adjuvants: A Versatile Approach to Combat Antibiotic Resistance. ACS OMEGA 2023; 8:10757-10783. [PMID: 37008128 PMCID: PMC10061514 DOI: 10.1021/acsomega.3c00312] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 02/21/2023] [Indexed: 06/13/2023]
Abstract
The problem of antibiotic resistance is on the rise, with multidrug-resistant strains emerging even to the last resort antibiotics. The drug discovery process is often stalled by stringent cut-offs required for effective drug design. In such a scenario, it is prudent to delve into the varying mechanisms of resistance to existing antibiotics and target them to improve antibiotic efficacy. Nonantibiotic compounds called antibiotic adjuvants which target bacterial resistance can be used in combination with obsolete drugs for an improved therapeutic regime. The field of "antibiotic adjuvants" has gained significant traction in recent years where mechanisms other than β-lactamase inhibition have been explored. This review discusses the multitude of acquired and inherent resistance mechanisms employed by bacteria to resist antibiotic action. The major focus of this review is how to target these resistance mechanisms by the use of antibiotic adjuvants. Different types of direct acting and indirect resistance breakers are discussed including enzyme inhibitors, efflux pump inhibitors, inhibitors of teichoic acid synthesis, and other cellular processes. The multifaceted class of membrane-targeting compounds with poly pharmacological effects and the potential of host immune-modulating compounds have also been reviewed. We conclude with providing insights about the existing challenges preventing clinical translation of different classes of adjuvants, especially membrane-perturbing compounds, and a framework about the possible directions which can be pursued to fill this gap. Antibiotic-adjuvant combinatorial therapy indeed has immense potential to be used as an upcoming orthogonal strategy to conventional antibiotic discovery.
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Affiliation(s)
- Geetika Dhanda
- Antimicrobial
Research Laboratory, New Chemistry Unit and School of Advanced
Materials, Jawaharlal Nehru Centre for Advanced
Scientific Research (JNCASR), Jakkur, Bengaluru 560064, Karnataka, India
| | - Yash Acharya
- Antimicrobial
Research Laboratory, New Chemistry Unit and School of Advanced
Materials, Jawaharlal Nehru Centre for Advanced
Scientific Research (JNCASR), Jakkur, Bengaluru 560064, Karnataka, India
| | - Jayanta Haldar
- Antimicrobial
Research Laboratory, New Chemistry Unit and School of Advanced
Materials, Jawaharlal Nehru Centre for Advanced
Scientific Research (JNCASR), Jakkur, Bengaluru 560064, Karnataka, India
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4
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Fischer TR, Meidner L, Schwickert M, Weber M, Zimmermann RA, Kersten C, Schirmeister T, Helm M. Chemical biology and medicinal chemistry of RNA methyltransferases. Nucleic Acids Res 2022; 50:4216-4245. [PMID: 35412633 PMCID: PMC9071492 DOI: 10.1093/nar/gkac224] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 03/17/2022] [Accepted: 04/08/2022] [Indexed: 12/24/2022] Open
Abstract
RNA methyltransferases (MTases) are ubiquitous enzymes whose hitherto low profile in medicinal chemistry, contrasts with the surging interest in RNA methylation, the arguably most important aspect of the new field of epitranscriptomics. As MTases become validated as drug targets in all major fields of biomedicine, the development of small molecule compounds as tools and inhibitors is picking up considerable momentum, in academia as well as in biotech. Here we discuss the development of small molecules for two related aspects of chemical biology. Firstly, derivates of the ubiquitous cofactor S-adenosyl-l-methionine (SAM) are being developed as bioconjugation tools for targeted transfer of functional groups and labels to increasingly visible targets. Secondly, SAM-derived compounds are being investigated for their ability to act as inhibitors of RNA MTases. Drug development is moving from derivatives of cosubstrates towards higher generation compounds that may address allosteric sites in addition to the catalytic centre. Progress in assay development and screening techniques from medicinal chemistry have led to recent breakthroughs, e.g. in addressing human enzymes targeted for their role in cancer. Spurred by the current pandemic, new inhibitors against coronaviral MTases have emerged at a spectacular rate, including a repurposed drug which is now in clinical trial.
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Affiliation(s)
- Tim R Fischer
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University Mainz, Staudingerweg 5, 55128Mainz, Germany
| | - Laurenz Meidner
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University Mainz, Staudingerweg 5, 55128Mainz, Germany
| | - Marvin Schwickert
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University Mainz, Staudingerweg 5, 55128Mainz, Germany
| | - Marlies Weber
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University Mainz, Staudingerweg 5, 55128Mainz, Germany
| | - Robert A Zimmermann
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University Mainz, Staudingerweg 5, 55128Mainz, Germany
| | - Christian Kersten
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University Mainz, Staudingerweg 5, 55128Mainz, Germany
| | - Tanja Schirmeister
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University Mainz, Staudingerweg 5, 55128Mainz, Germany
| | - Mark Helm
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University Mainz, Staudingerweg 5, 55128Mainz, Germany
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Crystal structure and functional analysis of mycobacterial erythromycin resistance methyltransferase Erm38 reveals its RNA binding site. J Biol Chem 2022; 298:101571. [PMID: 35007529 PMCID: PMC8844858 DOI: 10.1016/j.jbc.2022.101571] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 12/29/2021] [Accepted: 12/30/2021] [Indexed: 02/04/2023] Open
Abstract
Erythromycin resistance methyltransferases (Erms) confer resistance to macrolide, lincosamide, and streptogramin antibiotics in Gram-positive bacteria and mycobacteria. Although structural information for ErmAM, ErmC, and ErmE exists from Gram-positive bacteria, little is known about the Erms in mycobacteria, as there are limited biochemical data and no structures available. Here, we present crystal structures of Erm38 from Mycobacterium smegmatis in apoprotein and cofactor-bound forms. Based on structural analysis and mutagenesis, we identified several catalytically critical, positively charged residues at a putative RNA-binding site. We found that mutation of any of these sites is sufficient to abolish methylation activity, whereas the corresponding RNA-binding affinity of Erm38 remains unchanged. The methylation reaction thus appears to require a precise ensemble of amino acids to accurately position the RNA substrate, such that the target nucleotide can be methylated. In addition, we computationally constructed a model of Erm38 in complex with a 32-mer RNA substrate. This model shows the RNA substrate stably bound to Erm38 by a patch of positively charged residues. Furthermore, a π-π stacking interaction between a key aromatic residue of Erm38 and a target adenine of the RNA substrate forms a critical interaction needed for methylation. Taken together, these data provide valuable insights into Erm–RNA interactions, which will aid subsequent structure-based drug design efforts.
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Potential Target Site for Inhibitors in MLS B Antibiotic Resistance. Antibiotics (Basel) 2021; 10:antibiotics10030264. [PMID: 33807634 PMCID: PMC7998614 DOI: 10.3390/antibiotics10030264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 02/24/2021] [Accepted: 02/24/2021] [Indexed: 11/17/2022] Open
Abstract
Macrolide-lincosamide-streptogramin B antibiotic resistance occurs through the action of erythromycin ribosome methylation (Erm) family proteins, causing problems due to their prevalence and high minimal inhibitory concentration, and feasibilities have been sought to develop inhibitors. Erms exhibit high conservation next to the N-terminal end region (NTER) as in ErmS, 64SQNF67. Side chains of homologous S, Q and F in ErmC' are surface-exposed, located closely together and exhibit intrinsic flexibility; these residues form a motif X. In S64 mutations, S64G, S64A and S64C exhibited 71%, 21% and 20% activity compared to the wild-type, respectively, conferring cell resistance. However, mutants harboring larger side chains did not confer resistance and retain the methylation activity in vitro. All mutants of Q65, Q65N, Q65E, Q65R, and Q65H lost their methyl group transferring activity in vivo and in vitro. At position F67, a size reduction of side-chain (F67A) or a positive charge (F67H) greatly reduced the activity to about 4% whereas F67L with a small size reduction caused a moderate loss, more than half of the activity. The increased size by F67Y and F67W reduced the activity by about 75%. In addition to stabilization of the cofactor, these amino acids could interact with substrate RNA near the methylatable adenine presumably to be catalytically well oriented with the SAM (S-adenosyl-L-methionine). These amino acids together with the NTER beside them could serve as unique potential inhibitor development sites. This region constitutes a divergent element due to the NTER which has variable length and distinct amino acids context in each Erm. The NTER or part of it plays critical roles in selective recognition of substrate RNA by Erms and this presumed target site might assume distinct local structure by induced conformational change with binding to substrate RNA and SAM, and contribute to the specific recognition of substrate RNA.
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7
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Abstract
Many antibiotics available in the clinic today directly inhibit bacterial translation. Despite the past success of such drugs, their efficacy is diminishing with the spread of antibiotic resistance. Through the use of ribosomal modifications, ribosomal protection proteins, translation elongation factors and mistranslation, many pathogens are able to establish resistance to common therapeutics. However, current efforts in drug discovery are focused on overcoming these obstacles through the modification or discovery of new treatment options. Here, we provide an overview for common mechanisms of resistance to translation-targeting drugs and summarize several important breakthroughs in recent drug development.
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Affiliation(s)
- Anne Witzky
- 1 Department of Molecular Genetics, Ohio State University , Columbus, OH 43210 , USA.,2 Center for RNA Biology, Ohio State University , Columbus, OH 43210 , USA
| | - Rodney Tollerson
- 2 Center for RNA Biology, Ohio State University , Columbus, OH 43210 , USA.,3 Department of Microbiology, Ohio State University , Columbus, OH 43210 , USA
| | - Michael Ibba
- 2 Center for RNA Biology, Ohio State University , Columbus, OH 43210 , USA.,3 Department of Microbiology, Ohio State University , Columbus, OH 43210 , USA
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Drug combinations: a strategy to extend the life of antibiotics in the 21st century. Nat Rev Microbiol 2019; 17:141-155. [PMID: 30683887 DOI: 10.1038/s41579-018-0141-x] [Citation(s) in RCA: 449] [Impact Index Per Article: 89.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 11/22/2018] [Indexed: 01/03/2023]
Abstract
Antimicrobial resistance threatens a resurgence of life-threatening bacterial infections and the potential demise of many aspects of modern medicine. Despite intensive drug discovery efforts, no new classes of antibiotics have been developed into new medicines for decades, in large part owing to the stringent chemical, biological and pharmacological requisites for effective antibiotic drugs. Combinations of antibiotics and of antibiotics with non-antibiotic activity-enhancing compounds offer a productive strategy to address the widespread emergence of antibiotic-resistant strains. In this Review, we outline a theoretical and practical framework for the development of effective antibiotic combinations.
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9
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Foik IP, Tuszynska I, Feder M, Purta E, Stefaniak F, Bujnicki JM. Novel inhibitors of the rRNA ErmC' methyltransferase to block resistance to macrolides, lincosamides, streptogramine B antibiotics. Eur J Med Chem 2018; 146:60-67. [DOI: 10.1016/j.ejmech.2017.11.032] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 10/10/2017] [Accepted: 11/13/2017] [Indexed: 12/31/2022]
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10
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Vermote A, Van Calenbergh S. Small-Molecule Potentiators for Conventional Antibiotics against Staphylococcus aureus. ACS Infect Dis 2017; 3:780-796. [PMID: 28889735 DOI: 10.1021/acsinfecdis.7b00084] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Antimicrobial resistance constitutes a global health problem, while the discovery and development of novel antibiotics is stagnating. Methicillin-resistant Staphylococcus aureus, responsible for the establishment of recalcitrant, biofilm-related infections, is a well-known and notorious example of a highly resistant micro-organism. Since resistance development is unavoidable with conventional antibiotics that target bacterial viability, it is vital to develop alternative treatment options on top. Strategies aimed at more subtle manipulation of bacterial behavior have recently attracted attention. Here, we provide a literature overview of several small-molecule potentiators for antibiotics, identified for the treatment of Staphylococcus aureus infection. Typically, these potentiators are not bactericidal by themselves and function by reversing resistance mechanisms, by attenuating Staphylococcus aureus virulence, and/or by interfering with quorum sensing.
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Affiliation(s)
- Arno Vermote
- Laboratory for Medicinal Chemistry, Ghent University, Ottergemsesteenweg 460, B-9000 Ghent, Belgium
| | - Serge Van Calenbergh
- Laboratory for Medicinal Chemistry, Ghent University, Ottergemsesteenweg 460, B-9000 Ghent, Belgium
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11
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Mou KT, Muppirala UK, Severin AJ, Clark TA, Boitano M, Plummer PJ. A comparative analysis of methylome profiles of Campylobacter jejuni sheep abortion isolate and gastroenteric strains using PacBio data. Front Microbiol 2015; 5:782. [PMID: 25642218 PMCID: PMC4294202 DOI: 10.3389/fmicb.2014.00782] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Accepted: 12/20/2014] [Indexed: 12/13/2022] Open
Abstract
Campylobacter jejuni is a leading cause of human gastrointestinal disease and small ruminant abortions in the United States. The recent emergence of a highly virulent, tetracycline-resistant C. jejuni subsp. jejuni sheep abortion clone (clone SA) in the United States, and that strain's association with human disease, has resulted in a heightened awareness of the zoonotic potential of this organism. Pacific Biosciences' Single Molecule, Real-Time sequencing technology was used to explore the variation in the genome-wide methylation patterns of the abortifacient clone SA (IA3902) and phenotypically distinct gastrointestinal-specific C. jejuni strains (NCTC 11168 and 81-176). Several notable differences were discovered that distinguished the methylome of IA3902 from that of 11168 and 81-176: identification of motifs novel to IA3902, genome-specific hypo- and hypermethylated regions, strain level variability in genes methylated, and differences in the types of methylation motifs present in each strain. These observations suggest a possible role of methylation in the contrasting disease presentations of these three C. jejuni strains. In addition, the methylation profiles between IA3902 and a luxS mutant were explored to determine if variations in methylation patterns could be identified that might explain the role of LuxS-dependent methyl recycling in IA3902 abortifacient potential.
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Affiliation(s)
- Kathy T Mou
- Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University Ames, IA, USA
| | - Usha K Muppirala
- Genome Informatics Facility, Office of Biotechnology, Iowa State University Ames, IA, USA
| | - Andrew J Severin
- Genome Informatics Facility, Office of Biotechnology, Iowa State University Ames, IA, USA
| | | | | | - Paul J Plummer
- Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University Ames, IA, USA
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12
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Speculative strategies for new antibacterials: all roads should not lead to Rome. J Antibiot (Tokyo) 2013; 66:371-86. [PMID: 23612725 DOI: 10.1038/ja.2013.27] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Revised: 03/07/2013] [Accepted: 03/11/2013] [Indexed: 12/28/2022]
Abstract
In concert with improvements in personal hygiene and public sanitation, the discovery and development of antibiotics during the latter half of the last century has reduced substantially the morbidity and mortality associated with bacterial diseases. However, the past decade has witnessed a sharp reduction in interest in antibacterial drug development by 'big pharma', compounded by a decline in the breadth of chemical space for new antibacterial molecules and a failure to exploit the plethora of cellular processes potentially targetable by novel classes of antibacterial molecules. This review focuses on some strategies relating to antibacterial chemotherapy, paths less trodden, which the author considers worthy of further exploration.
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Bernal P, Molina-Santiago C, Daddaoua A, Llamas MA. Antibiotic adjuvants: identification and clinical use. Microb Biotechnol 2013; 6:445-9. [PMID: 23445397 PMCID: PMC3918149 DOI: 10.1111/1751-7915.12044] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Affiliation(s)
- Patricia Bernal
- Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas-CSIC, 18008 Granada, Spain
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14
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Pieren M, Tigges M. Adjuvant strategies for potentiation of antibiotics to overcome antimicrobial resistance. Curr Opin Pharmacol 2012; 12:551-5. [PMID: 22835931 DOI: 10.1016/j.coph.2012.07.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Revised: 07/05/2012] [Accepted: 07/06/2012] [Indexed: 12/17/2022]
Abstract
Alarming facts about the occurrence and spreading of multiple antibiotic resistant bacteria have caught the attention of global surveillance authorities and public media. The demand for novel effective antimicrobial drugs is high and on the rise while, at the same time, the supply of fresh 'magic bullets' is drying up. This review summarizes examples of recent strategies for development of adjunctive antibiotic therapies that overcome microbial resistance and thus rejuvenate the existing arsenal of drugs. Recent studies have demonstrated the potential of compounds that inhibit the action of the repressor protein implicated in ethionamide resistance, thus stimulating activation of the drug and thereby restoring the activity of the antibiotic for treatment of Mycobacterium tuberculosis. Such specific interference with regulators or signal transduction mechanisms involved in antibiotic resistance or virulence provides a new toolbox for novel combinations of antimicrobial drugs with adjuvant molecules lacking intrinsic antibiotic activity. In addition to the development of new antibiotics and vaccination initiatives this strategy of restoring or potentiating the activity of existing antibiotics may help to postpone the day when antibiotics are no longer generally efficacious.
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Affiliation(s)
- Michel Pieren
- BioVersys AG, Hochbergerstrasse 60c, c/o Technologycenter, CH-4057 Basel, Switzerland
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15
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McCusker KP, Fujimori DG. The chemistry of peptidyltransferase center-targeted antibiotics: enzymatic resistance and approaches to countering resistance. ACS Chem Biol 2012; 7:64-72. [PMID: 22208312 DOI: 10.1021/cb200418f] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The continued ability to treat bacterial infections requires effective antibiotics. The development of new therapeutics is guided by knowledge of the mechanisms of action of and resistance to these antibiotics. Continued efforts to understand and counteract antibiotic resistance mechanisms at a molecular level have the potential to direct development of new therapeutic strategies in addition to providing insight into the underlying biochemical functions impacted by antibiotics. The interaction of antibiotics with the peptidyltransferase center and adjacent exit tunnel within the bacterial ribosome is the predominant mechanism by which antibiotics impede translation, thus stalling growth. Resistance enzymes catalyze the chemical modification of the RNA that composes these functional regions, leading to diminished binding of antibiotics. This review discusses recent advances in the elucidation of chemical mechanisms underlying resistance and driving the development of new antibiotics.
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Affiliation(s)
- Kevin P. McCusker
- Department of Cellular and Molecular Pharmacology and ‡Department of Pharmaceutical Chemistry, University of California, San Francisco, 600 16th St, MC2280, San Francisco, California 94158, United States
| | - Danica Galonić Fujimori
- Department of Cellular and Molecular Pharmacology and ‡Department of Pharmaceutical Chemistry, University of California, San Francisco, 600 16th St, MC2280, San Francisco, California 94158, United States
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Shin WH, Heo L, Lee J, Ko J, Seok C, Lee J. LigDockCSA: Protein-ligand docking using conformational space annealing. J Comput Chem 2011; 32:3226-32. [DOI: 10.1002/jcc.21905] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Revised: 06/17/2011] [Accepted: 07/06/2011] [Indexed: 11/12/2022]
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17
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Abstract
The unremitting emergence of multidrug-resistant bacterial pathogens highlights a matching need for new therapeutic options. For example, new carbapenemases such as KPC (class A Klebsiella pneumoniae) and NDM-1 (New Delhi metallo-β-lactamase 1) are surfacing, resulting in almost total resistance to β-lactam antibiotics. Furthermore, resistance is quickly disseminated, not only in the healthcare sector, but also within the community at large, because many resistance determinants are carried on mobile genetic elements readily shared among pathogens. The absence of new antibiotics has led to a growing reliance on older, more toxic drugs such as colistin, but resistance to these is already arising. One approach to combat this growing problem is the use of combination drug antibiotic adjuvant therapy, which potentiates the activity of antibiotics. Here, we review the current situation and discuss potential drug combinations that may increase the potency of antibiotics in the future. Adjuvant therapies include antibiotic combinations, synergy between antibiotics and nonantibiotics, inhibition of resistance and molecules that alter the physiology of antibiotic-insensitive cells, such as those in biofilms. We provide a rationale for these multicomponent strategies, highlighting current research and important considerations for their clinical use and pharmacological properties.
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18
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Hansen LH, Lobedanz S, Douthwaite S, Arar K, Wengel J, Kirpekar F, Vester B. Minimal substrate features for Erm methyltransferases defined by using a combinatorial oligonucleotide library. Chembiochem 2011; 12:610-4. [PMID: 21264994 DOI: 10.1002/cbic.201000606] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Indexed: 11/08/2022]
Abstract
Erm methyltransferases are prevalent in pathogenic bacteria and confer resistance to macrolide, lincosamide, and streptogramin B antibiotics by specifically methylating the 23S ribosomal RNA at nucleotide A2058. We have identified motifs within the rRNA substrate that are required for methylation by Erm. Substrate molecules were constructed in a combinatorial manner from two separate sets (top and bottom strands) of short RNA sequences. Modifications, including LNA monomers with locked sugar residues, were incorporated into the substrates to stabilize their structures. In functional substrates, the A2058 methylation target (on the 13- to 19-nucleotide top strand) was displayed in an unpaired sequence immediately following a conserved irregular helix, and these are the specific structural features recognized by Erm. Erm methylation was enhanced by stabilizing the top-strand conformation with an LNA residue at G2056. The bottom strand (nine to 19 nucleotides in length) was required for methylation and was still functional after extensive modification, including substitution with a DNA sequence. Although it remains possible that Erm makes some unspecific contact with the bottom strand, the main role played by the bottom strand appears to be in maintaining the conformation of the top strand. The addition of multiple LNA residues to the top strand impeded methylation; this indicates that the RNA substrate requires a certain amount of flexibility for accommodation into the active site of Erm. The combinatorial approach for identifying small but functional RNA substrates is a step towards making RNA-Erm complexes suitable for cocrystal determination, and for designing molecules that might block the substrate-recognition site of the enzyme.
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Affiliation(s)
- Lykke H Hansen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
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19
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Structural rearrangements in the active site of the Thermus thermophilus 16S rRNA methyltransferase KsgA in a binary complex with 5'-methylthioadenosine. J Mol Biol 2009; 388:271-82. [PMID: 19285505 DOI: 10.1016/j.jmb.2009.02.066] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2008] [Revised: 01/16/2009] [Accepted: 02/28/2009] [Indexed: 11/21/2022]
Abstract
Posttranscriptional modification of ribosomal RNA (rRNA) occurs in all kingdoms of life. The S-adenosyl-L-methionine-dependent methyltransferase KsgA introduces the most highly conserved rRNA modification, the dimethylation of A1518 and A1519 of 16S rRNA. Loss of this dimethylation confers resistance to the antibiotic kasugamycin. Here, we report biochemical studies and high-resolution crystal structures of KsgA from Thermus thermophilus. Methylation of 30S ribosomal subunits by T. thermophilus KsgA is more efficient at low concentrations of magnesium ions, suggesting that partially unfolded RNA is the preferred substrate. The overall structure is similar to that of other methyltransferases but contains an additional alpha-helix in a novel N-terminal extension. Comparison of the apoenzyme with complex structures with 5'-methylthioadenosine or adenosine bound in the cofactor-binding site reveals novel features when compared with related enzymes. Several mobile loop regions that restrict access to the cofactor-binding site are observed. In addition, the orientation of residues in the substrate-binding site indicates that conformational changes are required for binding two adjacent residues of the substrate rRNA.
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