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Liu X, Boelter G, Vollmer W, Banzhaf M, den Blaauwen T. Peptidoglycan Endopeptidase PBP7 Facilitates the Recruitment of FtsN to the Divisome and Promotes Peptidoglycan Synthesis in Escherichia coli. Mol Microbiol 2024. [PMID: 39344863 DOI: 10.1111/mmi.15321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2024] [Revised: 09/07/2024] [Accepted: 09/10/2024] [Indexed: 10/01/2024]
Abstract
Escherichia coli has many periplasmic hydrolases to degrade and modify peptidoglycan (PG). However, the redundancy of eight PG endopeptidases makes it challenging to define specific roles to individual enzymes. Therefore, the cellular role of PBP7 (encoded by pbpG) is not clearly defined. In this work, we show that PBP7 localizes in the lateral cell envelope and at midcell. The C-terminal α-helix of PBP7 is crucial for midcell localization but not for its activity, which is dispensable for this localization. Additionally, midcell localization of PBP7 relies on the assembly of FtsZ up to FtsN in the divisome, and on the activity of PBP3. PBP7 was found to affect the assembly timing of FtsZ and FtsN in the divisome. The absence of PBP7 slows down the assembly of FtsN at midcell. The ΔpbpG mutant exhibited a weaker incorporation of the fluorescent D-amino acid HADA, reporting on transpeptidase activity, compared to wild-type cells. This could indicate reduced PG synthesis at the septum of the ΔpbpG strain, explaining the slower accumulation of FtsN and suggesting that endopeptidase-mediated PG cleavage may be a rate-limiting step for septal PG synthesis.
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Affiliation(s)
- Xinwei Liu
- Bacterial Cell Biology and Physiology, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam, The Netherlands
| | - Gabriela Boelter
- Institute of Microbiology & Infection and School of Biosciences, University of Birmingham, Edgbaston, Birmingham, UK
| | - Waldemar Vollmer
- Centre for Bacterial Cell Biology, Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Framlington Place, Newcastle upon Tyne, UK
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Manuel Banzhaf
- Institute of Microbiology & Infection and School of Biosciences, University of Birmingham, Edgbaston, Birmingham, UK
- Centre for Bacterial Cell Biology, Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Framlington Place, Newcastle upon Tyne, UK
| | - Tanneke den Blaauwen
- Bacterial Cell Biology and Physiology, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam, The Netherlands
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Li R, Lichstrahl MS, Zandi TA, Kahlert L, Townsend CA. The dabABC operon is a marker of C4-alkylated monobactam biosynthesis and responsible for ( 2S, 3R)-diaminobutyrate production. iScience 2024; 27:109202. [PMID: 38433893 PMCID: PMC10906522 DOI: 10.1016/j.isci.2024.109202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 01/12/2024] [Accepted: 02/07/2024] [Indexed: 03/05/2024] Open
Abstract
Non-ribosomal peptide synthetases (NRPSs) assemble metabolites of medicinal and commercial value. Both serine and threonine figure prominently in these processes and separately can be converted to the additional NRPS building blocks 2,3-diaminopropionate (Dap) and 2,3-diaminobutyrate (Dab). Here we bring extensive bioinformatics, in vivo and in vitro experimentation to compose a unified view of the biosynthesis of these widely distributed non-canonical amino acids that both derive by pyridoxal-mediated β-elimination of the activated O-phosphorylated substrates followed by β-addition of an amine donor. By examining monobactam biosynthesis in Pseudomonas and in Burkholderia species where it is silent, we show that (2S,3R)-Dab synthesis depends on an l-threonine kinase (DabA), a β-replacement reaction with l-aspartate (DabB) and an argininosuccinate lyase-like protein (DabC). The growing clinical importance of monobactams to both withstand Ambler Class B metallo-β-lactamases and retain their antibiotic activity make reprogrammed precursor and NRPS synthesis of modified monobactams a feasible and attractive goal.
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Affiliation(s)
- Rongfeng Li
- Department of Chemistry, The Johns Hopkins University, 3400 N Charles St, Baltimore, MD, USA
| | - Michael S. Lichstrahl
- Department of Chemistry, The Johns Hopkins University, 3400 N Charles St, Baltimore, MD, USA
| | - Trevor A. Zandi
- T. C. Jenkins Department of Biophysics, The Johns Hopkins University, Baltimore, MD, USA
| | - Lukas Kahlert
- Department of Chemistry, The Johns Hopkins University, 3400 N Charles St, Baltimore, MD, USA
| | - Craig A. Townsend
- Department of Chemistry, The Johns Hopkins University, 3400 N Charles St, Baltimore, MD, USA
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Verheul J, Lodge A, Yau HCL, Liu X, Boelter G, Liu X, Solovyova AS, Typas A, Banzhaf M, Vollmer W, den Blaauwen T. Early midcell localization of Escherichia coli PBP4 supports the function of peptidoglycan amidases. PLoS Genet 2022; 18:e1010222. [PMID: 35604931 PMCID: PMC9166362 DOI: 10.1371/journal.pgen.1010222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 06/03/2022] [Accepted: 04/27/2022] [Indexed: 11/24/2022] Open
Abstract
Insertion of new material into the Escherichia coli peptidoglycan (PG) sacculus between the cytoplasmic membrane and the outer membrane requires a well-organized balance between synthetic and hydrolytic activities to maintain cell shape and avoid lysis. Since most bacteria carry multiple enzymes carrying the same type of PG hydrolytic activity, we know little about the specific function of given enzymes. Here we show that the DD-carboxy/endopeptidase PBP4 localizes in a PBP1A/LpoA and FtsEX dependent fashion at midcell during septal PG synthesis. Midcell localization of PBP4 requires its non-catalytic domain 3 of unknown function, but not the activity of PBP4 or FtsE. Microscale thermophoresis with isolated proteins shows that PBP4 interacts with NlpI and the FtsEX-interacting protein EnvC, an activator of amidases AmiA and AmiB, which are needed to generate denuded glycan strands to recruit the initiator of septal PG synthesis, FtsN. The domain 3 of PBP4 is needed for the interaction with NlpI and EnvC, but not PBP1A or LpoA. In vivo crosslinking experiments confirm the interaction of PBP4 with PBP1A and LpoA. We propose that the interaction of PBP4 with EnvC, whilst not absolutely necessary for mid-cell recruitment of either protein, coordinates the activities of PBP4 and the amidases, which affects the formation of denuded glycan strands that attract FtsN. Consistent with this model, we found that the divisome assembly at midcell was premature in cells lacking PBP4, illustrating how the complexity of interactions affect the timing of cell division initiation. Peptidoglycan biosynthesis is a major target for antibacterials. The covalently closed peptidoglycan mesh, called sacculus, protects the bacterium from lysis due to its turgor. Sacculus growth is facilitated by the balanced activities of synthases and hydrolases, and disturbing this balance leads to cell lysis and bacterial death. Because of the large number and possible redundant functions of peptidoglycan hydrolases, it has been difficult to decipher their individual functions. In this paper we show that the DD-endopeptidase PBP4 localizes at midcell during septal peptidoglycan synthesis in Escherichia coli and is involved in the timing of the assembly and activation of the division machinery. This shows that inhibition of certain hydrolases could weaken the cells and might enhance antibiotic action.
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Affiliation(s)
- Jolanda Verheul
- Bacterial Cell Biology, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam, The Netherlands
| | - Adam Lodge
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Hamish C. L. Yau
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Xiaolong Liu
- Bacterial Cell Biology, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam, The Netherlands
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Gabriela Boelter
- Institute of Microbiology & Infection and School of Biosciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - Xinwei Liu
- Bacterial Cell Biology, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam, The Netherlands
| | | | - Athanasios Typas
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
- European Molecular Biology Laboratory, Structural & Computational Unit, Heidelberg, Germany
| | - Manuel Banzhaf
- Institute of Microbiology & Infection and School of Biosciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
- * E-mail: (MB); (WV); (TdB)
| | - Waldemar Vollmer
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
- * E-mail: (MB); (WV); (TdB)
| | - Tanneke den Blaauwen
- Bacterial Cell Biology, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam, The Netherlands
- * E-mail: (MB); (WV); (TdB)
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Turner J, Muraoka A, Bedenbaugh M, Childress B, Pernot L, Wiencek M, Peterson YK. The Chemical Relationship Among Beta-Lactam Antibiotics and Potential Impacts on Reactivity and Decomposition. Front Microbiol 2022; 13:807955. [PMID: 35401470 PMCID: PMC8988990 DOI: 10.3389/fmicb.2022.807955] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 02/14/2022] [Indexed: 12/05/2022] Open
Abstract
Beta-lactam antibiotics remain one of the most commonly prescribed drug classes, but they are limited by their propensity to cause hypersensitivity reactions (e.g., from allergy to anaphylaxis) as well as by the emergence of bacteria with a myriad of resistance mechanisms such as β-lactamases. While development efforts continue to focus on overcoming resistance, there are ongoing concerns regarding cross-contamination of β-lactams during manufacturing and compounding of these drugs. Additionally, there is a need to reduce levels of drugs such as β-lactam antibiotics in waste-water to mitigate the risk of environmental exposure. To help address future development of effective remediation chemistries and processes, it is desired to better understand the structural relationship among the most common β-lactams. This study includes the creation of a class-wide structural ordering of the entire β-lactam series, including both United States Food and Drug Association (US-FDA)-approved drugs and experimental therapies. The result is a structural relational map: the "Lactamome," which positions each substance according to architecture and chemical end-group. We utilized a novel method to compare the structural relationships of β-lactam antibiotics among the radial cladogram and describe the positioning with respect to efficacy, resistance to hydrolysis, reported hypersensitivity, and Woodward height. The resulting classification scheme may help with the development of broad-spectrum treatments that reduce the risk of occupational exposure and negative environmental impacts, assist practitioners with avoiding adverse patient reactions, and help direct future drug research.
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Affiliation(s)
- Jonathan Turner
- College of Medicine, Medical University of South Carolina, Charleston, SC, United States
- College of Pharmacy, Medical University of South Carolina, Charleston, SC, United States
| | - Alyssa Muraoka
- College of Pharmacy, Medical University of South Carolina, Charleston, SC, United States
| | | | - Blaine Childress
- South Carolina Research Authority, Greenville, SC, United States
| | | | | | - Yuri K. Peterson
- College of Pharmacy, Medical University of South Carolina, Charleston, SC, United States
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Kaur R, Rani P, Atanasov AG, Alzahrani Q, Gupta R, Kapoor B, Gulati M, Chawla P. Discovery and Development of Antibacterial Agents: Fortuitous and Designed. Mini Rev Med Chem 2021; 22:984-1029. [PMID: 34939541 DOI: 10.2174/1570193x19666211221150119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2021] [Revised: 10/18/2021] [Accepted: 10/25/2021] [Indexed: 11/22/2022]
Abstract
Today, antibacterial drug resistance has turned into a significant public health issue. Repeated intake, suboptimal and/or unnecessary use of antibiotics, and, additionally, the transfer of resistance genes are the critical elements that make microorganisms resistant to conventional antibiotics. A substantial number of antibacterials that were successfully utilized earlier for prophylaxis and therapeutic purposes have been rendered inadequate due to this phenomenon. Therefore, the exploration of new molecules has become a continuous endeavour. Many such molecules are at various stages of investigation. A surprisingly high number of new molecules are currently in the stage of phase 3 clinical trials. A few new agents have been commercialized in the last decade. These include solithromycin, plazomicin, lefamulin, omadacycline, eravacycline, delafloxacin, zabofloxacin, finafloxacin, nemonoxacin, gepotidacin, zoliflodacin, cefiderocol, BAL30072, avycaz, zerbaxa, vabomere, relebactam, tedizolid, cadazolid, sutezolid, triclosan and afabiacin. This article aims to review the investigational and recently approved antibacterials with a focus on their structure, mechanisms of action/resistance, and spectrum of activity. Delving deep, their success or otherwise in various phases of clinical trials is also discussed while attributing the same to various causal factors.
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Affiliation(s)
- Ravleen Kaur
- Department of Health Sciences, Cape Breton University, Sydney, Nova Scotia. Canada
| | - Pooja Rani
- School of Pharmaceutical Sciences, Lovely Professional University, Phagwara. India
| | - Atanas G Atanasov
- Ludwig Boltzmann Institute of Digital Health and Patient Safety, Medical University of Vienna, Vienna. Austria
| | - Qushmua Alzahrani
- Department of Pharmacy/Nursing/Medicine Health and Environment, University of the Region of Joinville (UNIVILLE) volunteer researcher, Joinville. Brazil
| | - Reena Gupta
- School of Pharmaceutical Sciences, Lovely Professional University, Phagwara . India
| | - Bhupinder Kapoor
- School of Pharmaceutical Sciences, Lovely Professional University, Phagwara . India
| | - Monica Gulati
- School of Pharmaceutical Sciences, Lovely Professional University, Phagwara . India
| | - Pooja Chawla
- Department of Pharmaceutical Chemistry and Analysis, ISF College of Pharmacy, Ghal Kalan Moga, Punjab 142001. India
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Liu R, Miller PA, Miller MJ. Conjugation of Aztreonam, a Synthetic Monocyclic β-Lactam Antibiotic, to a Siderophore Mimetic Significantly Expands Activity Against Gram-Negative Bacteria. ACS Infect Dis 2021; 7:2979-2986. [PMID: 34668698 DOI: 10.1021/acsinfecdis.1c00458] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Monocyclic β-lactams with antibiotic activity were first synthesized more than 40 years ago. Extensive early structure-activity relationship (SAR) studies, especially in the 1980s, emphasized the need for heteroatom activation of monocyclic β-lactams and led to studies of oxamazins, monobactams, monosulfactams, and monocarbams with various side chains and peripheral substitution that revealed potent activity against select strains of Gram-negative bacteria. Aztreonam, still the only clinically used monobactam, has notable activity against many Gram-negative bacteria but limited activity against some of the most problematic multidrug resistant (MDR) strains of Pseudomonas aeruginosa and Acinetobacter baumannii. Herein, we report that extension of the side chain of aztreonam is tolerated and especially that coupling of the side chain free acid with a bis-catechol siderophore mimetic significantly improves activity against the MDR strains of Gram-negative bacteria that are of most significant concern.
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Affiliation(s)
- Rui Liu
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Patricia A. Miller
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Marvin J. Miller
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
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Recruitment of the TolA protein to cell constriction sites in Escherichia coli via three separate mechanisms, and a critical role for FtsWI activity in recruitment of both TolA and TolQ. J Bacteriol 2021; 204:e0046421. [PMID: 34748387 DOI: 10.1128/jb.00464-21] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The Tol-Pal system of Gram-negative bacteria helps maintain integrity of the cell envelope and ensures that invagination of the envelope layers during cell fission occurs in a well-coordinated manner. In E. coli, the five Tol-Pal proteins (TolQ, R, A, B and Pal) accumulate at cell constriction sites in a manner that normally requires the activity of the cell constriction initiation protein FtsN. While septal recruitment of TolR, TolB and Pal also requires the presence of TolQ and/or TolA, each of the the latter two can recognize constriction sites independently of the other system proteins. What attracts TolQ or TolA to these sites is unclear. We show that FtsN attracts both proteins in an indirect fashion, and that PBP1A, PBP1B and CpoB are dispensable for their septal recruitment. However, the β-lactam aztreonam readily interferes with septal accumulation of both TolQ and TolA, indicating that FtsN-stimulated production of septal peptidoglycan by the FtsWI synthase is critical to their recruitment. We also discovered that each of TolA's three domains can recognize division sites in a separate fashion. Notably, the middle domain (TolAII) is responsible for directing TolA to constriction sites in the absence of other Tol-Pal proteins and CpoB, while recruitment of TolAI and TolAIII requires TolQ and a combination of TolB, Pal, and CpoB, respectively. Additionally, we describe the construction and use of functional fluorescent sandwich fusions of the ZipA division protein, which should be more broadly valuable in future studies of the E. coli cell division machinery. IMPORTANCE Cell division (cytokinesis) is a fundamental biological process that is incompletely understood for any organism. Division of bacterial cells relies on a ring-like machinery called the septal ring or divisome that assembles along the circumference of the mother cell at the site where constriction will eventually occur. In the well-studied bacterium Escherichia coli, this machinery contains over thirty distinct proteins. We studied how two such proteins, TolA and TolQ, which also play a role in maintaining integrity of the outer-membrane, are recruited to the machinery. We find that TolA can be recruited by three separate mechanisms, and that both proteins rely on the activity of a well-studied cell division enzyme for their recruitment.
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Bahr G, González LJ, Vila AJ. Metallo-β-lactamases in the Age of Multidrug Resistance: From Structure and Mechanism to Evolution, Dissemination, and Inhibitor Design. Chem Rev 2021; 121:7957-8094. [PMID: 34129337 PMCID: PMC9062786 DOI: 10.1021/acs.chemrev.1c00138] [Citation(s) in RCA: 106] [Impact Index Per Article: 35.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Antimicrobial resistance is one of the major problems in current practical medicine. The spread of genes coding for resistance determinants among bacteria challenges the use of approved antibiotics, narrowing the options for treatment. Resistance to carbapenems, last resort antibiotics, is a major concern. Metallo-β-lactamases (MBLs) hydrolyze carbapenems, penicillins, and cephalosporins, becoming central to this problem. These enzymes diverge with respect to serine-β-lactamases by exhibiting a different fold, active site, and catalytic features. Elucidating their catalytic mechanism has been a big challenge in the field that has limited the development of useful inhibitors. This review covers exhaustively the details of the active-site chemistries, the diversity of MBL alleles, the catalytic mechanism against different substrates, and how this information has helped developing inhibitors. We also discuss here different aspects critical to understand the success of MBLs in conferring resistance: the molecular determinants of their dissemination, their cell physiology, from the biogenesis to the processing involved in the transit to the periplasm, and the uptake of the Zn(II) ions upon metal starvation conditions, such as those encountered during an infection. In this regard, the chemical, biochemical and microbiological aspects provide an integrative view of the current knowledge of MBLs.
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Affiliation(s)
- Guillermo Bahr
- Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Universidad Nacional de Rosario, Ocampo y Esmeralda S/N, 2000 Rosario, Argentina
- Area Biofísica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina
| | - Lisandro J. González
- Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Universidad Nacional de Rosario, Ocampo y Esmeralda S/N, 2000 Rosario, Argentina
- Area Biofísica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina
| | - Alejandro J. Vila
- Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Universidad Nacional de Rosario, Ocampo y Esmeralda S/N, 2000 Rosario, Argentina
- Area Biofísica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina
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Lima LM, Silva BNMD, Barbosa G, Barreiro EJ. β-lactam antibiotics: An overview from a medicinal chemistry perspective. Eur J Med Chem 2020; 208:112829. [DOI: 10.1016/j.ejmech.2020.112829] [Citation(s) in RCA: 96] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 09/06/2020] [Accepted: 09/07/2020] [Indexed: 11/27/2022]
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Vrancianu CO, Gheorghe I, Dobre EG, Barbu IC, Cristian RE, Popa M, Lee SH, Limban C, Vlad IM, Chifiriuc MC. Emerging Strategies to Combat β-Lactamase Producing ESKAPE Pathogens. Int J Mol Sci 2020; 21:E8527. [PMID: 33198306 PMCID: PMC7697847 DOI: 10.3390/ijms21228527] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 11/09/2020] [Accepted: 11/10/2020] [Indexed: 02/06/2023] Open
Abstract
Since the discovery of penicillin by Alexander Fleming in 1929 as a therapeutic agent against staphylococci, β-lactam antibiotics (BLAs) remained the most successful antibiotic classes against the majority of bacterial strains, reaching a percentage of 65% of all medical prescriptions. Unfortunately, the emergence and diversification of β-lactamases pose indefinite health issues, limiting the clinical effectiveness of all current BLAs. One solution is to develop β-lactamase inhibitors (BLIs) capable of restoring the activity of β-lactam drugs. In this review, we will briefly present the older and new BLAs classes, their mechanisms of action, and an update of the BLIs capable of restoring the activity of β-lactam drugs against ESKAPE (Enterococcus spp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) pathogens. Subsequently, we will discuss several promising alternative approaches such as bacteriophages, antimicrobial peptides, nanoparticles, CRISPR (clustered regularly interspaced short palindromic repeats) cas technology, or vaccination developed to limit antimicrobial resistance in this endless fight against Gram-negative pathogens.
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Affiliation(s)
- Corneliu Ovidiu Vrancianu
- Microbiology Immunology Department and The Research Institute of the University of Bucharest, Faculty of Biology, University of Bucharest, 020956 Bucharest, Romania; (C.O.V.); (E.-G.D.); (I.C.B.); (M.P.); (M.C.C.)
| | - Irina Gheorghe
- Microbiology Immunology Department and The Research Institute of the University of Bucharest, Faculty of Biology, University of Bucharest, 020956 Bucharest, Romania; (C.O.V.); (E.-G.D.); (I.C.B.); (M.P.); (M.C.C.)
| | - Elena-Georgiana Dobre
- Microbiology Immunology Department and The Research Institute of the University of Bucharest, Faculty of Biology, University of Bucharest, 020956 Bucharest, Romania; (C.O.V.); (E.-G.D.); (I.C.B.); (M.P.); (M.C.C.)
| | - Ilda Czobor Barbu
- Microbiology Immunology Department and The Research Institute of the University of Bucharest, Faculty of Biology, University of Bucharest, 020956 Bucharest, Romania; (C.O.V.); (E.-G.D.); (I.C.B.); (M.P.); (M.C.C.)
| | - Roxana Elena Cristian
- Department of Biochemistry and Molecular Biology, Faculty of Biology, University of Bucharest, 020956 Bucharest, Romania;
| | - Marcela Popa
- Microbiology Immunology Department and The Research Institute of the University of Bucharest, Faculty of Biology, University of Bucharest, 020956 Bucharest, Romania; (C.O.V.); (E.-G.D.); (I.C.B.); (M.P.); (M.C.C.)
| | - Sang Hee Lee
- Department of Biological Sciences, Myongji University, 03674 Myongjiro, Yongin 449-728, Gyeonggido, Korea;
- National Leading Research Laboratory, Department of Biological Sciences, Myongji University, 116 Myongjiro, Yongin 17058, Gyeonggido, Korea
| | - Carmen Limban
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, “Carol Davila” University of Medicine and Pharmacy, Traian Vuia no.6, 020956 Bucharest, Romania; (C.L.); (I.M.V.)
| | - Ilinca Margareta Vlad
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, “Carol Davila” University of Medicine and Pharmacy, Traian Vuia no.6, 020956 Bucharest, Romania; (C.L.); (I.M.V.)
| | - Mariana Carmen Chifiriuc
- Microbiology Immunology Department and The Research Institute of the University of Bucharest, Faculty of Biology, University of Bucharest, 020956 Bucharest, Romania; (C.O.V.); (E.-G.D.); (I.C.B.); (M.P.); (M.C.C.)
- Academy of Romanian Scientists, 030167 Bucharest, Romania
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Therapeutic Effect and Mechanisms of the Novel Monosulfactam 0073. Antimicrob Agents Chemother 2020; 64:AAC.00529-20. [PMID: 32718961 DOI: 10.1128/aac.00529-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 07/08/2020] [Indexed: 02/05/2023] Open
Abstract
This study aimed to evaluate the antimicrobial activity of the novel monosulfactam 0073 against multidrug-resistant Gram-negative bacteria in vitro and in vivo and to characterize the mechanisms underlying 0073 activity. The in vitro activities of 0073, aztreonam, and the combination with avibactam were assessed by MIC and time-kill assays. The safety of 0073 was evaluated using 3-(4,5-dimethylthizol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and acute toxicity assays. Murine thigh infection and pneumonia models were employed to define in vivo efficacy. A penicillin-binding protein (PBP) competition assay and confocal microscopy were conducted. The inhibitory action of 0073 against β-lactamases was evaluated by the half-maximal inhibitory concentration (IC50), and resistance development was evaluated via serial passage. The monosulfactam 0073 showed promising antimicrobial activity against Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter baumannii isolates producing metallo-β-lactamases (MBLs) and serine β-lactamases. In preliminary experiments, compound 0073 exhibited safety both in vitro and in vivo In the murine thigh infection model and the pneumonia models in which infection was induced by P. aeruginosa and Klebsiella pneumoniae, 0073 significantly reduced the bacterial burden. Compound 0073 targeted several PBPs and exerted inhibitory effects against some serine β-lactamases. Finally, 0073 showed a reduced propensity for resistance selection compared with that of aztreonam. The novel monosulfactam 0073 exhibited increased activity against β-lactamase-producing Gram-negative organisms compared with the activity of aztreonam and showed good safety profiles both in vitro and in vivo The underlying mechanisms may be attributed to the affinity of 0073 for several PBPs and its inhibitory activity against some serine β-lactamases. These data indicate that 0073 represents a potential treatment for infections caused by β-lactamase-producing multidrug-resistant bacteria.
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Antimicrobials as Single and Combination Therapy for Colistin-Resistant Pseudomonas aeruginosa at a University Hospital in Thailand. Antibiotics (Basel) 2020; 9:antibiotics9080475. [PMID: 32756327 PMCID: PMC7459651 DOI: 10.3390/antibiotics9080475] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 07/29/2020] [Accepted: 07/31/2020] [Indexed: 11/24/2022] Open
Abstract
Global infections with colistin-resistant Pseudomonas aeruginosa (CoR-PA) are increasing; there are currently very few studies focused on the antimicrobial susceptibility of CoR-PA isolates, and none from Thailand. Here, we investigated the impact of various antimicrobials, alone and in combination, via the in vitro testing of CoR-PA clinical isolates. Eighteen CoR-PA isolates were obtained from patients treated at Phramongkutklao Hospital from January 2010 through June 2019; these were classified into six different clonal types by using the enterobacterial repetitive intergenic consensus (ERIC)-PCR method, with a high prevalence of Group A (27.8%). The antimicrobial susceptibility was determined as the minimal inhibitory concentrations (MICs) using the epsilometer-test (E-test) method. The synergistic activities of six antimicrobial combinations were reported via the fractional-inhibitory-concentration index. All CoR-PA isolates were susceptible to amikacin, meropenem, and ceftolozane/tazobactam, but only 5.56% were susceptible to imipenem. In vitro synergistic activities were detected for amikacin with aztreonam, piperacillin/tazobactam, meropenem, and ceftazidime for 16.67%, 11.11%, 11.11%, and 5.55%, respectively. One CoR-PA isolate carried the blaVIM metallo-β-lactamase gene; none carried mcr-1 genes or detected plasmid-mediated AmpC β-lactamase or an overproduction of chromosomal AmpC β-lactamase. Seven CoR-PA isolates (38.89%) were capable of biofilm formation. In conclusion, CoR-PA isolates are highly susceptible to antimicrobials; the synergy observed in response to the various agents should be examined in a clinical setting.
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13
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Ferrer-Espada R, Sánchez-Gómez S, Pitts B, Stewart PS, Martínez-de-Tejada G. Permeability enhancers sensitize β-lactamase-expressing Enterobacteriaceae and Pseudomonas aeruginosa to β-lactamase inhibitors, thereby restoring their β-lactam susceptibility. Int J Antimicrob Agents 2020; 56:105986. [PMID: 32335279 DOI: 10.1016/j.ijantimicag.2020.105986] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 04/07/2020] [Accepted: 04/08/2020] [Indexed: 11/16/2022]
Abstract
OBJECTIVES β-lactamases are the major resistance determinant for β-lactam antibiotics in Gram-negative bacteria. Although there are β-lactamase inhibitors (BLIs) available, β-lactam-BLI combinations are increasingly being neutralised by diverse mechanisms of bacterial resistance. This study hypothesised that permeability-increasing antimicrobial peptides (AMPs) could lower the amount of BLIs necessary to sensitise bacteria to antibiotics that are β-lactamase substrates. METHODS To test this hypothesis, checkerboard assays were performed to measure the ability of several AMPs to synergise with piperacillin, ticarcillin, amoxicillin, ampicillin, and ceftazidime in the presence of either tazobactam, clavulanic acid, sulbactam, aztreonam, phenylboronic acid (PBA), or oxacillin. Assays were performed using planktonic and biofilm-forming cells of Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae overexpressing β-lactamases. RESULTS Synergy between polymyxin B nonapeptide (PMBN) and tazobactam boosted piperacillin activity by a factor of 128 in Escherichia coli (from 256 to 2 mg/L, fractional inhibitory concentration index (FICI) ≤ 0.02) and by a factor of at least 64 in Klebsiella pneumoniae (from 1024 mg/L to 16 mg/L, FICI ≤ 0.05). Synergy between PMBN and PBA enhanced ceftazidime activity 133 times in Pseudomonas aeruginosa (from 16 mg/L to 0.12 mg/L, FICI ≤ 0.03). As a consequence, MICs of all the tested antibiotics were brought down to therapeutic range. In addition, the combinations also reduced several orders of magnitude the amount of inhibitor needed for antibiotic sensitisation. Ceftazidime/PBA/PMBN at 50 times the planktonic MIC caused a 10 million-fold reduction in the viability of mature biofilms. CONCLUSION This study proved that AMPs can synergise with BLIs and that this phenomenon can be exploited to sensitise bacteria to antibiotics.
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Affiliation(s)
- Raquel Ferrer-Espada
- University of Navarra, Department of Microbiology and Parasitology, Pamplona, Spain; Navarra Institute for Health Research (idiSNA), Pamplona, Spain.
| | | | - Betsey Pitts
- Center for Biofilm Engineering, Montana State University, Bozeman, Mt, USA
| | - Philip S Stewart
- Center for Biofilm Engineering, Montana State University, Bozeman, Mt, USA
| | - Guillermo Martínez-de-Tejada
- University of Navarra, Department of Microbiology and Parasitology, Pamplona, Spain; Navarra Institute for Health Research (idiSNA), Pamplona, Spain
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14
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Fuiano G, Sepe V, Viscione M, Nani E, Conte G. Effectiveness of Single Daily Intraperitoneal Administration of Aztreonam and Cefuroxime in the Treatment of Peritonitis in Continuous Ambulatory Peritoneal Dialysis (CAPD). Perit Dial Int 2020. [DOI: 10.1177/089686088900900408] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
To discover if the management of peritonitis in continuous ambulatory peritoneal dialysis (CAPD) may be effectively simplified by single daily i.p. administration of aztreonam (A) and cefuroxime (C), 10 adult CAPD patients (pts) with peritonitis were trained to start the following treatment procedure: a) sterile collection of dialysate effluent for cultures; b) 4 rapid in-and-out exchanges with antibiotic free dialysate; c) addition of 2 g C and 2 g A to a 2-L exchange for 6-h dwell time (the same dosage was repeated once a day in the overnight exchange); d) routine CAPD exchanges. Concentrations of C and A were measured in dialysate and serum of the patients 2, 12, 18, and 21–23 h after the i.p. administration: C remained within therapeutic range in all samples, while serum and dialysate A levels fell below such range 16 h after the i.p. administration. Seventeen peritonitis episodes occurred during the observation period (12 months): initial dialysate cultures grew Staph. aureus in 6 episodes, Staph epidermidis in 6, Pseudomonas aer. in 2, Streptococcus faecalis in 1, Citrobacter in 1, and Candida in 1. All patients but 1 (with Candida-positive culture) responded to this treatment with no relapse in 2 months. We conclude that once a day i.p. administration of 2 g aztreonam plus 2 g of cefuroxime is an effective and simple way of treating CAPD pts with gram-positive and gram-negative peritonitis.
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Affiliation(s)
- G. Fuiano
- Departments of Nephrology, Faculty of Medicine of Catanzaro
| | - V. Sepe
- Departments of Nephrology, Faculty of Medicine of Catanzaro
| | - M. Viscione
- Departments of Nephrology, Faculty of Medicine of Catanzaro
| | - E. Nani
- Microbiology, 2nd Faculty of Medicine of Naples, Faculty of Medicine of Catanzaro
| | - G. Conte
- Department of Nephrology, Faculty of Medicine of Catanzaro
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15
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Lu Z, Wang H, Zhang A, Liu X, Zhou W, Yang C, Guddat L, Yang H, Schofield CJ, Rao Z. Structures of Mycobacterium tuberculosis Penicillin-Binding Protein 3 in Complex with Five β-Lactam Antibiotics Reveal Mechanism of Inactivation. Mol Pharmacol 2020; 97:287-294. [DOI: 10.1124/mol.119.118042] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 01/14/2020] [Indexed: 11/22/2022] Open
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16
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Gordon EM, Duncton MAJ, Wang BJ, Qi L, Fan D, Li X, Ni ZJ, Ding P, Grygorash R, Low E, Yu G, Sun J. Toward Orally Absorbed Prodrugs of the Antibiotic Aztreonam. Design of Novel Prodrugs of Sulfate Containing Drugs. Part 2. ACS Med Chem Lett 2020; 11:162-165. [PMID: 32071683 DOI: 10.1021/acsmedchemlett.9b00534] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 01/08/2020] [Indexed: 11/30/2022] Open
Abstract
Aztreonam, first discovered in 1980, is an FDA approved, intravenous, monocyclic beta-lactam antibiotic. Aztreonam is active against Gram-negative bacteria and is still used today. The oral bioavailability of aztreonam in humans is less than 1%. Herein we describe the design and synthesis of potential oral prodrugs of aztreonam.
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Affiliation(s)
- Eric M Gordon
- Arixa Pharmaceuticals, 525 University Avenue, Suite 1350, Palo Alto, California 94301, United States
| | - Matthew A J Duncton
- Arixa Pharmaceuticals, 525 University Avenue, Suite 1350, Palo Alto, California 94301, United States
| | - Brian J Wang
- Synterys, Inc., 29540 Kohoutek Way, Union City, California 94587, United States
| | - Longwu Qi
- Acme Bioscience, Inc., 3941 East Bayshore Road, Palo Alto, California 94303, United States
| | - Dazhong Fan
- Acme Bioscience, Inc., 3941 East Bayshore Road, Palo Alto, California 94303, United States
| | - Xianfeng Li
- Acme Bioscience, Inc., 3941 East Bayshore Road, Palo Alto, California 94303, United States
| | - Zhi-Jie Ni
- Acme Bioscience, Inc., 3941 East Bayshore Road, Palo Alto, California 94303, United States
| | - Pingyu Ding
- Synterys, Inc., 29540 Kohoutek Way, Union City, California 94587, United States
| | - Ruslan Grygorash
- Synterys, Inc., 29540 Kohoutek Way, Union City, California 94587, United States
| | - Eddy Low
- Synterys, Inc., 29540 Kohoutek Way, Union City, California 94587, United States
| | - Guijun Yu
- Synterys, Inc., 29540 Kohoutek Way, Union City, California 94587, United States
| | - Jiawei Sun
- Synterys, Inc., 29540 Kohoutek Way, Union City, California 94587, United States
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17
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Ferreira RJ, Kasson PM. Antibiotic Uptake Across Gram-Negative Outer Membranes: Better Predictions Towards Better Antibiotics. ACS Infect Dis 2019; 5:2096-2104. [PMID: 31593635 DOI: 10.1021/acsinfecdis.9b00201] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Crossing the Gram-negative bacterial membrane poses a major barrier to antibiotic development, as many small molecules that can biochemically inhibit key bacterial processes are rendered microbiologically ineffective by their poor cellular uptake. The outer membrane is the major permeability barrier for many drug-like molecules, and the chemical properties that enable efficient uptake into mammalian cells fail to predict bacterial uptake. We have developed a computational method for accurate prospective prediction of outer membrane uptake of drug-like molecules, which we combine with a new medium-throughput experimental assay of outer membrane vesicle swelling. Parallel molecular dynamics simulations of compound uptake through Escherichia coli (E. coli) OmpF are used to successfully and quantitatively predict experimental permeabilities measured via either outer membrane swelling or prior liposome-swelling measurements. These simulations are analyzed using an inhomogeneous solubility-diffusion model to yield predictions of permeability. For most polar molecules we test, outer membrane permeability also correlates well with whole-cell uptake. The ability to accurately predict and measure outer membrane uptake of a wide variety of small molecules will enable simpler determination of which molecular scaffolds and which derivatives are most promising prior to extensive chemical synthesis. It will also assist in formulating a more systematic understanding of the chemical determinants of outer membrane permeability.
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Affiliation(s)
- Ricardo J. Ferreira
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Box 596, 75124 Uppsala, Sweden
| | - Peter M. Kasson
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Box 596, 75124 Uppsala, Sweden
- Departments of Biomedical Engineering and Molecular Physiology and Biological Physics, University of Virginia, Box 800886, Charlottesville, Virginia 22908, United States
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18
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El-Shorbagi AN, Chaudhary S. Monobactams: A Unique Natural Scaffold of Four-Membered Ring Skeleton, Recent Development to Clinically Overcome Infections by Multidrug- Resistant Microbes. LETT DRUG DES DISCOV 2019. [DOI: 10.2174/1570180816666190516113202] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Background:
Monobactam antibiotics have been testified to demonstrate significant antibacterial
activity especially the treatment of infections by superbug microbes. Recently, research has
been focused on the structural modifications, and new generation of this privileged natural scaffold.
Objective:
Efforts have been made to discover the structure-antibacterial relationship of monbactams
in order to avoid the aimless work involving the ongoing generated analogues. This review aims to
summarize the current knowledge and development of monobactams as a broad-spectrum antibacterial
scaffolds. The recent structural modifications that expand the activity, especially in the infections
by resistant-strains, combinational therapies and dosing, as well as the possibility of crosshypersensitivity/
reactivity/tolerability with penicillins and cephalosporins will also be summarized
and inferred. Different approaches will be covered with emphasis on chemical methods and Structure-
Activity Relationship (SAR), in addition to the proposed mechanisms of action. Clinical investigation
of monobactams tackling various aspects will not be missed in this review.
Conclusion:
The conclusion includes the novels approaches, that could be followed to design new
research projects and reduce the pitfalls in the future development of monobactams.
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Affiliation(s)
- Abdel Nasser El-Shorbagi
- Department of Medicinal Chemistry, College of Pharmacy, University of Sharjah, Sharjah 27272, United Arab Emirates
| | - Sachin Chaudhary
- Department of Medicinal Chemistry, College of Pharmacy, University of Sharjah, Sharjah 27272, United Arab Emirates
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19
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Targeting the Nonmevalonate Pathway in Burkholderia cenocepacia Increases Susceptibility to Certain β-Lactam Antibiotics. Antimicrob Agents Chemother 2018; 62:AAC.02607-17. [PMID: 29439968 DOI: 10.1128/aac.02607-17] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 02/07/2018] [Indexed: 11/20/2022] Open
Abstract
The nonmevalonate pathway is the sole pathway for isoprenoid biosynthesis in Burkholderia cenocepacia and is possibly a novel target for the development of antibacterial chemotherapy. The goals of the present study were to evaluate the essentiality of dxr, the second gene of the nonmevalonate pathway, in B. cenocepacia and to determine whether interfering with the nonmevalonate pathway increases susceptibility toward antibiotics. To this end, a rhamnose-inducible conditional dxr knockdown mutant of B. cenocepacia strain K56-2 (B. cenocepacia K56-2dxr) was constructed, using a plasmid which enables the delivery of a rhamnose-inducible promoter in the chromosome. Expression of dxr is essential for bacterial growth; the growth defect observed in the dxr mutant could be complemented by expressing dxr in trans under the control of a constitutive promoter, but not by providing 2-C-methyl-d-erythritol-4-phosphate, the reaction product of DXR (1-deoxy-d-xylulose 5-phosphate reductoisomerase). B. cenocepacia K56-2dxr showed markedly increased susceptibility to the β-lactam antibiotics aztreonam, ceftazidime, and cefotaxime, while susceptibility to other antibiotics was not (or was much less) affected; this increased susceptibility could also be complemented by in trans expression of dxr A similarly increased susceptibility was observed when antibiotics were combined with FR900098, a known DXR inhibitor. Our data confirm that the nonmevalonate pathway is essential in B. cenocepacia and suggest that combining potent DXR inhibitors with selected β-lactam antibiotics is a useful strategy to combat B. cenocepacia infections.
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20
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Carosso S, Liu R, Miller PA, Hecker SJ, Glinka T, Miller MJ. Methodology for Monobactam Diversification: Syntheses and Studies of 4-Thiomethyl Substituted β-Lactams with Activity against Gram-Negative Bacteria, Including Carbapenemase Producing Acinetobacter baumannii. J Med Chem 2017; 60:8933-8944. [PMID: 28994597 DOI: 10.1021/acs.jmedchem.7b01164] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Bromine induced lactamization of vinyl acetohydroxamates facilitated syntheses of monocyclic β-lactams suitable for incorporation of a thiomethyl and extended functionality at the C(4) position. Elaboration of the resulting substituted N-hydroxy-2-azetidinones allowed incorporation of functionalized α-amino substituents appropriate for enhancement of antibiotic activity. Evaluation of antibacterial activity against a panel of Gram-positive and Gram-negative bacteria revealed structure-activity relationships (SAR) and identification of potent new monobactam antibiotics. The corresponding bis-catechol conjugate, 42, has excellent activity against Gram-negative bacteria including carbapenemase and carbacephalosporinase producing strains of Acinetobacter baumannii, which have been listed by the WHO as being of critical concern worldwide.
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Affiliation(s)
- Serena Carosso
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Rui Liu
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Patricia A Miller
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
| | - Scott J Hecker
- Rempex Pharmaceuticals, The Medicines Company , 3013 Science Park Road, First Floor, San Diego, California 92121, United States
| | - Tomasz Glinka
- Rempex Pharmaceuticals, The Medicines Company , 3013 Science Park Road, First Floor, San Diego, California 92121, United States
| | - Marvin J Miller
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
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21
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Talele TT. Natural-Products-Inspired Use of the gem-Dimethyl Group in Medicinal Chemistry. J Med Chem 2017; 61:2166-2210. [DOI: 10.1021/acs.jmedchem.7b00315] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Tanaji T. Talele
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John’s University, Queens, New York 11439, United States
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22
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Polar delivery of Legionella type IV secretion system substrates is essential for virulence. Proc Natl Acad Sci U S A 2017; 114:8077-8082. [PMID: 28696299 DOI: 10.1073/pnas.1621438114] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
A recurrent emerging theme is the targeting of proteins to subcellular microdomains within bacterial cells, particularly to the poles. In most cases, it has been assumed that this localization is critical to the protein's function. Legionella pneumophila uses a type IVB secretion system (T4BSS) to export a large number of protein substrates into the cytoplasm of host cells. Here we show that the Legionella export apparatus is localized to the bacterial poles, as is consistent with many T4SS substrates being retained on the phagosomal membrane adjacent to the poles of the bacterium. More significantly, we were able to demonstrate that polar secretion of substrates is critically required for Legionella's alteration of the host endocytic pathway, an activity required for this pathogen's virulence.
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23
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Mazuski JE, Tessier JM, May AK, Sawyer RG, Nadler EP, Rosengart MR, Chang PK, O'Neill PJ, Mollen KP, Huston JM, Diaz JJ, Prince JM. The Surgical Infection Society Revised Guidelines on the Management of Intra-Abdominal Infection. Surg Infect (Larchmt) 2017; 18:1-76. [PMID: 28085573 DOI: 10.1089/sur.2016.261] [Citation(s) in RCA: 331] [Impact Index Per Article: 47.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Previous evidence-based guidelines on the management of intra-abdominal infection (IAI) were published by the Surgical Infection Society (SIS) in 1992, 2002, and 2010. At the time the most recent guideline was released, the plan was to update the guideline every five years to ensure the timeliness and appropriateness of the recommendations. METHODS Based on the previous guidelines, the task force outlined a number of topics related to the treatment of patients with IAI and then developed key questions on these various topics. All questions were approached using general and specific literature searches, focusing on articles and other information published since 2008. These publications and additional materials published before 2008 were reviewed by the task force as a whole or by individual subgroups as to relevance to individual questions. Recommendations were developed by a process of iterative consensus, with all task force members voting to accept or reject each recommendation. Grading was based on the GRADE (Grades of Recommendation Assessment, Development, and Evaluation) system; the quality of the evidence was graded as high, moderate, or weak, and the strength of the recommendation was graded as strong or weak. Review of the document was performed by members of the SIS who were not on the task force. After responses were made to all critiques, the document was approved as an official guideline of the SIS by the Executive Council. RESULTS This guideline summarizes the current recommendations developed by the task force on the treatment of patients who have IAI. Evidence-based recommendations have been made regarding risk assessment in individual patients; source control; the timing, selection, and duration of antimicrobial therapy; and suggested approaches to patients who fail initial therapy. Additional recommendations related to the treatment of pediatric patients with IAI have been included. SUMMARY The current recommendations of the SIS regarding the treatment of patients with IAI are provided in this guideline.
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Affiliation(s)
- John E Mazuski
- 1 Department of Surgery, Washington University School of Medicine , Saint Louis, Missouri
| | | | - Addison K May
- 3 Department of Surgery, Vanderbilt University , Nashville, Tennessee
| | - Robert G Sawyer
- 4 Department of Surgery, University of Virginia , Charlottesville, Virginia
| | - Evan P Nadler
- 5 Division of Pediatric Surgery, Children's National Medical Center , Washington, DC
| | - Matthew R Rosengart
- 6 Department of Surgery, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Phillip K Chang
- 7 Department of Surgery, University of Kentucky , Lexington, Kentucky
| | | | - Kevin P Mollen
- 9 Division of Pediatric Surgery, Department of Surgery, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Jared M Huston
- 10 Department of Surgery, Hofstra Northwell School of Medicine , Hempstead, New York
| | - Jose J Diaz
- 11 Department of Surgery, University of Maryland School of Medicine , Baltimore, Maryland
| | - Jose M Prince
- 12 Departments of Surgery and Pediatrics, Hofstra-Northwell School of Medicine , Hempstead, New York
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24
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Abstract
Aztreonam is the first synthetic monobactam to undergo clinical studies in the U.S. Aztreonam has excellent activity against P. aeruginosa and Enterobacteriaceae, but poor activity against anaerobic and gram-positive organisms. Aztreonam has poor oral bioavailability, but can be given intramuscularly or intravenously in doses of 1–2 g q6–12h. Clinical trials of aztreonam have shown it to be effective in infections of urine, lung, skin, blood, bones and joints, and abdomen with an adverse reaction profile similar to β-lactams. Aztreonam may be an alternate to aminoglycoside therapy, with the advantage of not being nephrotoxic.
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25
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Xu H, Zhou W, Zhou D, Li J, Al-Huniti N. Evaluation of Aztreonam Dosing Regimens in Patients With Normal and Impaired Renal Function: A Population Pharmacokinetic Modeling and Monte Carlo Simulation Analysis. J Clin Pharmacol 2016; 57:336-344. [DOI: 10.1002/jcph.810] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 08/10/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Hongmei Xu
- Quantitative Clinical Pharmacology; AstraZeneca; Waltham MA USA
| | - Wangda Zhou
- Quantitative Clinical Pharmacology; AstraZeneca; Waltham MA USA
| | - Diansong Zhou
- Quantitative Clinical Pharmacology; AstraZeneca; Waltham MA USA
| | - Jianguo Li
- Quantitative Clinical Pharmacology; AstraZeneca; Waltham MA USA
| | - Nidal Al-Huniti
- Quantitative Clinical Pharmacology; AstraZeneca; Waltham MA USA
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26
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Abstract
β-Lactams are the most widely used class of antibiotics. Since the discovery of benzylpenicillin in the 1920s, thousands of new penicillin derivatives and related β-lactam classes of cephalosporins, cephamycins, monobactams, and carbapenems have been discovered. Each new class of β-lactam has been developed either to increase the spectrum of activity to include additional bacterial species or to address specific resistance mechanisms that have arisen in the targeted bacterial population. Resistance to β-lactams is primarily because of bacterially produced β-lactamase enzymes that hydrolyze the β-lactam ring, thereby inactivating the drug. The newest effort to circumvent resistance is the development of novel broad-spectrum β-lactamase inhibitors that work against many problematic β-lactamases, including cephalosporinases and serine-based carbapenemases, which severely limit therapeutic options. This work provides a comprehensive overview of β-lactam antibiotics that are currently in use, as well as a look ahead to several new compounds that are in the development pipeline.
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Affiliation(s)
- Karen Bush
- Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405
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27
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Strawa J, Wajs-Bonikowska A, Leszczyńska K, Ściepuk M, Nazaruk J. Chemical composition and antioxidant, antibacterial activity of Cirsium rivulare (Jacq) All. roots. Nat Prod Res 2016; 30:2730-2733. [DOI: 10.1080/14786419.2016.1138303] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Jakub Strawa
- Department of Pharmacognosy, Medical University of Bialystok, Bialystok, Poland
| | - Anna Wajs-Bonikowska
- Institute of General Food Chemistry, Lodz University of Technology, Lodz, Poland
| | | | - Małgorzata Ściepuk
- Department of Microbiology, Medical University of Bialystok, Bialystok, Poland
| | - Jolanta Nazaruk
- Department of Pharmacognosy, Medical University of Bialystok, Bialystok, Poland
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28
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Characterization of Piperacillin/Tazobactam-Resistant Klebsiella oxytoca Recovered from a Nosocomial Outbreak. PLoS One 2015; 10:e0142366. [PMID: 26539828 PMCID: PMC4634934 DOI: 10.1371/journal.pone.0142366] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 10/21/2015] [Indexed: 11/19/2022] Open
Abstract
We characterized 12 clinical isolates of Klebsiella oxytoca with the extended-spectrum β-lactamase (ESBL) phenotype (high minimum inhibitory concentration [MIC] values of ceftriaxone) recovered over 9 months at a university hospital in Japan. To determine the clonality of the isolates, we used pulsed-field gel electrophoresis (PFGE), multi-locus sequence typing (MLST), and PCR analyses to detect blaRBI, which encodes the β-lactamase RbiA, OXY-2-4 with overproduce-type promoter. Moreover, we performed the isoelectric focusing (IEF) of β-lactamases, and the determination of the MICs of β-lactams including piperacillin/tazobactam for 12 clinical isolates and E. coli HB101 with pKOB23, which contains blaRBI, by the agar dilution method. Finally, we performed the initial screening and phenotypic confirmatory tests for ESBLs. Each of the 12 clinical isolates had an identical PFGE pulsotype and MLST sequence type (ST9). All 12 clinical isolates harbored identical blaRBI. The IEF revealed that the clinical isolate produced only one β-lactamase. E. coli HB101 (pKOB23) and all 12 isolates demonstrated equally resistance to piperacillin/tazobactam (MICs, >128 μg/ml). The phenotypic confirmatory test after the initial screening test for ESBLs can discriminate β-lactamase RbiA-producing K. oxytoca from β-lactamase CTX-M-producing K. oxytoca. Twelve clinical isolates of K. oxytoca, which were recovered from an outbreak at one university hospital, had identical genotypes and produced β-lactamase RbiA that conferred resistance to piperacillin/tazobactam. In order to detect K. oxytoca isolates that produce RbiA to promote research concerning β-lactamase RbiA-producing K. oxytoca, the phenotypic confirmatory test after the initial screening test for ESBLs would be useful.
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van der Ploeg R, Goudelis ST, den Blaauwen T. Validation of FRET Assay for the Screening of Growth Inhibitors of Escherichia coli Reveals Elongasome Assembly Dynamics. Int J Mol Sci 2015; 16:17637-54. [PMID: 26263980 PMCID: PMC4581212 DOI: 10.3390/ijms160817637] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 07/21/2015] [Accepted: 07/24/2015] [Indexed: 11/16/2022] Open
Abstract
The increase in antibiotic resistant bacteria demands the development of new antibiotics against preferably new targets. The common approach is to test compounds for their ability to kill bacteria or to design molecules that inhibit essential protein activities in vitro. In the first case, the mode of action of the drug is unknown and in the second case, it is not known whether the compound will pass the impermeable barrier of the bacterial envelope. We developed an assay that detects the target of a compound, as well as its ability to pass the membrane(s) simultaneously. The Escherichia coli cytoskeletal protein MreB recruits protein complexes (elongasomes) that are essential for cell envelope growth. An in cell Förster Resonance Energy Transfer (FRET) assay was developed to detect the interaction between MreB molecules and between MreB and the elongasome proteins RodZ, RodA and PBP2. Inhibition of the polymerization of MreB by S-(3,4-dichlorobenzyl) isothiourea (A22) or of the activity of PBP2 by mecilinam resulted in loss or reduction of all measured interactions. This suggests that the interactions between the elongasome proteins are governed by a combination of weak affinities and substrate availability. This validated in cell FRET assay can be used to screen for cell envelope growth inhibitors.
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Affiliation(s)
- René van der Ploeg
- Bacterial Cell Biology, Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherland.
| | - Spyridon Theodoros Goudelis
- Bacterial Cell Biology, Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherland.
| | - Tanneke den Blaauwen
- Bacterial Cell Biology, Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherland.
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Kocaoglu O, Carlson EE. Profiling of β-lactam selectivity for penicillin-binding proteins in Escherichia coli strain DC2. Antimicrob Agents Chemother 2015; 59:2785-90. [PMID: 25733506 PMCID: PMC4394777 DOI: 10.1128/aac.04552-14] [Citation(s) in RCA: 110] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 02/24/2015] [Indexed: 02/07/2023] Open
Abstract
Penicillin-binding proteins (PBPs) are integral players in bacterial cell division, and their catalytic activities can be monitored with β-lactam-containing chemical probes. Compounds that target a single PBP could provide important information about the specific role(s) of each enzyme, making identification of such molecules important. We evaluated 22 commercially available β-lactams for inhibition of the PBPs in live Escherichia coli strain DC2. Whole cells were titrated with β-lactam antibiotics and subsequently incubated with a fluorescent penicillin derivative, Bocillin-FL (Boc-FL), to label uninhibited PBPs. Protein visualization was accomplished by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) separation and fluorescent scanning. The examined β-lactams exhibited diverse PBP selectivities, with amdinocillin (mecillinam) showing selectivity for PBP2, aztreonam, piperacillin, cefuroxime, cefotaxime, and ceftriaxone for PBP3, and amoxicillin and cephalexin for PBP4. The remaining β-lactams did not block any PBPs in the DC2 strain of E. coli or inhibited more than one PBP at all examined concentrations in this Gram-negative organism.
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Affiliation(s)
- Ozden Kocaoglu
- Department of Molecular and Cellular Biochemistry, Indiana University Bloomington, Bloomington, Indiana, USA
| | - Erin E Carlson
- Department of Molecular and Cellular Biochemistry, Indiana University Bloomington, Bloomington, Indiana, USA Department of Chemistry, Indiana University Bloomington, Bloomington, Indiana, USA
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Murphy-Benenato KE, Bhagunde PR, Chen A, Davis HE, Durand-Réville TF, Ehmann DE, Galullo V, Harris JJ, Hatoum-Mokdad H, Jahić H, Kim A, Manjunatha MR, Manyak EL, Mueller J, Patey S, Quiroga O, Rooney M, Sha L, Shapiro AB, Sylvester M, Tan B, Tsai AS, Uria-Nickelsen M, Wu Y, Zambrowski M, Zhao SX. Discovery of Efficacious Pseudomonas aeruginosa-Targeted Siderophore-Conjugated Monocarbams by Application of a Semi-mechanistic Pharmacokinetic/Pharmacodynamic Model. J Med Chem 2015; 58:2195-205. [DOI: 10.1021/jm501506f] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | - M. R. Manjunatha
- Infection
Innovative Medicines, AstraZeneca India Pvt. Ltd., Bellary Road, Bangalore 560024, India
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Salinity-dependent impacts of ProQ, Prc, and Spr deficiencies on Escherichia coli cell structure. J Bacteriol 2014; 196:1286-96. [PMID: 24443528 DOI: 10.1128/jb.00827-13] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
ProQ is a cytoplasmic protein with RNA chaperone activities that reside in FinO- and Hfq-like domains. Lesions at proQ decrease the level of the osmoregulatory glycine betaine transporter ProP. Lesions at proQ eliminated ProQ and Prc, the periplasmic protease encoded by the downstream gene prc. They dramatically slowed the growth of Escherichia coli populations and altered the morphologies of E. coli cells in high-salinity medium. ProQ and Prc deficiencies were associated with different phenotypes. ProQ-deficient bacteria were elongated unless glycine betaine was provided. High-salinity cultures of Prc-deficient bacteria included spherical cells with an enlarged periplasm and an eccentric nucleoid. The nucleoid-containing compartment was bounded by the cytoplasmic membrane and peptidoglycan. This phenotype was not evident in bacteria cultivated at low or moderate salinity, nor was it associated with murein lipoprotein (Lpp) deficiency, and it differed from those elicited by the MreB inhibitor A-22 or the FtsI inhibitor aztreonam at low or high salinity. It was suppressed by deletion of spr, which encodes one of three murein hydrolases that are redundantly essential for enlargement of the murein sacculus. Prc deficiency may alter bacterial morphology by impairing control of Spr activity at high salinity. ProQ and Prc deficiencies lowered the ProP activity of bacteria cultivated at moderate salinity by approximately 70% and 30%, respectively, but did not affect other osmoregulatory functions. The effects of ProQ and Prc deficiencies on ProP activity are indirect, reflecting their roles in the maintenance of cell structure.
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Bycroft BW, Shute RE. The molecular basis for the mode of action of Beta-lactam antibiotics and mechanisms of resistance. Pharm Res 2013; 2:3-14. [PMID: 24272507 DOI: 10.1023/a:1016305704057] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
This review on the molecular basis for the mode of action of β-lactam antibiotics and mechanisms of resistance is divided into three main sections. Firstly, a brief introduction to the β-lactam antibiotic family is presented from the standpoint of their natural product origins. The second section is concerned with bacterial cell wall structure and biosynthesis, and the mode of action of β-lactam antibiotics. It includes an attempted rationalization of the multiple enzyme targets of penicillin, the so-called "penicillin binding proteins", into one or two lethal sites of action and the interaction of these enzymes with β-lactams in terms of their analogy to the natural substrate and to the substrate-enzyme transition state. The final part covers the phenomenon of bacterial resistance to β-lactam antibiotic therapy and deals with the two most important manifestations of resistance; permeability and the production of β-lactamases. This latter more crucial factor is then expanded with particular reference to the irreversible inhibition of these enzymes by suicide inactivators; a general theory for irreversible β-lactamase inhibition is discussed and the future prospects within this whole area are briefly overviewed.
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Affiliation(s)
- B W Bycroft
- Department of Pharmacy, University of Nottingham, UK
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Vieira M, Pinheiro C, Fernandes R, Noronha JP, Prudêncio C. Antimicrobial activity of quinoxaline 1,4-dioxide with 2- and 3-substituted derivatives. Microbiol Res 2013; 169:287-93. [PMID: 23928379 DOI: 10.1016/j.micres.2013.06.015] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 06/11/2013] [Accepted: 06/12/2013] [Indexed: 10/26/2022]
Abstract
Quinoxaline is a chemical compound that presents a structure that is similar to quinolone antibiotics. The present work reports the study of the antimicrobial activity of quinoxaline N,N-dioxide and some derivatives against bacterial and yeast strains. The compounds studied were quinoxaline-1,4-dioxide (QNX), 2-methylquinoxaline-1,4-dioxide (2MQNX), 2-methyl-3-benzoylquinoxaline-1,4-dioxide (2M3BenzoylQNX), 2-methyl-3-benzylquinoxaline-1,4-dioxide (2M3BQNX), 2-amino-3-cyanoquinoxaline-1,4-dioxide (2A3CQNX), 3-methyl-2-quinoxalinecarboxamide-1,4-dioxide (3M2QNXC), 2-hydroxyphenazine-N,N-dioxide (2HF) and 3-methyl-N-(2-methylphenyl)quinoxalinecarboxamide-1,4-dioxide (3MN(2MF)QNXC). The prokaryotic strains used were Staphylococcus aureus ATCC 6538, S. aureus ATCC 6538P, S. aureus ATCC 29213, Escherichia coli ATCC 25922, E. coli S3R9, E. coli S3R22, E. coli TEM-1 CTX-M9, E. coli TEM-1, E. coli AmpC Mox-2, E. coli CTX-M2 e E. coli CTX-M9. The Candida albicans ATCC 10231 and Saccharomyces cerevisiae PYCC 4072 were used as eukaryotic strains. For the compounds that presented activity using the disk diffusion method, the minimum inhibitory concentration (MIC) was determined. The alterations of cellular viability were evaluated in a time-course assay. Death curves for bacteria and growth curves for S. cerevisiae PYCC 4072 were also accessed. The results obtained suggest potential new drugs for antimicrobial activity chemotherapy since the MIC's determined present low values and cellular viability tests show the complete elimination of the bacterial strain. Also, the cellular viability tests for the eukaryotic model, S. cerevisiae, indicate low toxicity for the compounds tested.
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Affiliation(s)
- Mónica Vieira
- REQUIMTE/CQFB, Departamento de Química, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal; Ciências Químicas e das Biomoléculas, Centro de Investigação em Saúde e Ambiente, Escola Superior de Tecnologias da Saúde, Instituto Politécnico do Porto, Rua Valente Perfeito, 322, 4400-330 Vila Nova de Gaia, Portugal.
| | - Cátia Pinheiro
- Ciências Químicas e das Biomoléculas, Centro de Investigação em Saúde e Ambiente, Escola Superior de Tecnologias da Saúde, Instituto Politécnico do Porto, Rua Valente Perfeito, 322, 4400-330 Vila Nova de Gaia, Portugal
| | - Rúben Fernandes
- Ciências Químicas e das Biomoléculas, Centro de Investigação em Saúde e Ambiente, Escola Superior de Tecnologias da Saúde, Instituto Politécnico do Porto, Rua Valente Perfeito, 322, 4400-330 Vila Nova de Gaia, Portugal; Centro de Farmacologia e Biopatologia Química (U38-FCT), Faculdade de Medicina, Universidade do Porto, Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal
| | - João Paulo Noronha
- REQUIMTE/CQFB, Departamento de Química, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - Cristina Prudêncio
- Ciências Químicas e das Biomoléculas, Centro de Investigação em Saúde e Ambiente, Escola Superior de Tecnologias da Saúde, Instituto Politécnico do Porto, Rua Valente Perfeito, 322, 4400-330 Vila Nova de Gaia, Portugal; Centro de Farmacologia e Biopatologia Química (U38-FCT), Faculdade de Medicina, Universidade do Porto, Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal; CHUC, Centro Hospitalar da Universidade de Coimbra, Coimbra, Portugal
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Abstract
The beta-lactam family of antimicrobials, in particular penicillins and cephalosporins, is the mainstay of treatment for community-acquired infections. However, the emergence of resistant isolates to these agents has raised concerns regarding the continued efficacy of existing therapies. Resistance to beta-lactams is most commonly expressed by the microbial production of beta-lactamases that hydrolyze the beta-lactam ring. Three further resistance mechanisms include conformational changes in penicillin-binding proteins (PBPs); permeability changes in the outer membrane; and active efflux of the antimicrobial. In addition to the pre-requisite efficacy and tolerability profiles, new beta-lactams should address these four resistance mechanisms. Overcoming resistance may be a serendipitous event or arrived at by design. A unique synthetic beta-lactam class, which demonstrates promise in terms of its activity against the range of bacteria responsible for community-acquired infections and its inherent stability to hydrolysis by beta-lactamases, is the penems. This discrete class of hybrid molecules combines properties from the penicillin (penam) and cephalosporin (cephem) beta-lactam classes. Faropenem is an example of a penem with a broad spectrum of activity designed to address these resistance issues.
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Affiliation(s)
- S G B Amyes
- Medical Microbiology, University of Edinburgh Medical School, Teviot Place, Edinburgh, EH8 9AG, UK
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Zheng SY, Yu B, Zhang K, Chen M, Hua YH, Yuan S, Watt RM, Zheng BJ, Yuen KY, Huang JD. Comparative immunological evaluation of recombinant Salmonella Typhimurium strains expressing model antigens as live oral vaccines. BMC Immunol 2012; 13:54. [PMID: 23013063 PMCID: PMC3503649 DOI: 10.1186/1471-2172-13-54] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Accepted: 09/04/2012] [Indexed: 11/10/2022] Open
Abstract
Background Despite the development of various systems to generate live recombinant Salmonella Typhimurium vaccine strains, little work has been performed to systematically evaluate and compare their relative immunogenicity. Such information would provide invaluable guidance for the future rational design of live recombinant Salmonella oral vaccines. Result To compare vaccine strains encoded with different antigen delivery and expression strategies, a series of recombinant Salmonella Typhimurium strains were constructed that expressed either the enhanced green fluorescent protein (EGFP) or a fragment of the hemagglutinin (HA) protein from the H5N1 influenza virus, as model antigens. The antigens were expressed from the chromosome, from high or low-copy plasmids, or encoded on a eukaryotic expression plasmid. Antigens were targeted for expression in either the cytoplasm or the outer membrane. Combinations of strategies were employed to evaluate the efficacy of combined delivery/expression approaches. After investigating in vitro and in vivo antigen expression, growth and infection abilities; the immunogenicity of the constructed recombinant Salmonella strains was evaluated in mice. Using the soluble model antigen EGFP, our results indicated that vaccine strains with high and stable antigen expression exhibited high B cell responses, whilst eukaryotic expression or colonization with good construct stability was critical for T cell responses. For the insoluble model antigen HA, an outer membrane expression strategy induced better B cell and T cell responses than a cytoplasmic strategy. Most notably, the combination of two different expression strategies did not increase the immune response elicited. Conclusion Through systematically evaluating and comparing the immunogenicity of the constructed recombinant Salmonella strains in mice, we identified their respective advantages and deleterious or synergistic effects. Different construction strategies were optimally-required for soluble versus insoluble forms of the protein antigens. If an antigen, such as EGFP, is soluble and expressed at high levels, a low-copy plasmid-cytoplasmic expression strategy is recommended; since it provokes the highest B cell responses and also induces good T cell responses. If a T cell response is preferred, a eukaryotic expression plasmid or a chromosome-based, cytoplasmic-expression strategy is more effective. For insoluble antigens such as HA, an outer membrane expression strategy is recommended.
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Affiliation(s)
- Song-yue Zheng
- Department of Biochemistry, the University of Hong Kong, Pokfulam, Hong Kong
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Chang SC, Hsu TH, Chu YH, Lin HM, Lee MJ. Micronization of aztreonam with supercritical anti-solvent process. J Taiwan Inst Chem Eng 2012. [DOI: 10.1016/j.jtice.2012.04.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Yu Q, Griffin EF, Moreau-Marquis S, Schwartzman JD, Stanton BA, O'Toole GA. In vitro evaluation of tobramycin and aztreonam versus Pseudomonas aeruginosa biofilms on cystic fibrosis-derived human airway epithelial cells. J Antimicrob Chemother 2012; 67:2673-81. [PMID: 22843834 DOI: 10.1093/jac/dks296] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
OBJECTIVES Aztreonam for inhalation solution (AZLI) was recently approved by the FDA for treating cystic fibrosis (CF) patients infected with Pseudomonas aeruginosa. Here we investigated the effect of aztreonam alone or in combination with tobramycin on P. aeruginosa biofilms grown on CF airway epithelial cells. METHODS P. aeruginosa biofilms, produced by laboratory strains or clinical isolates, were formed on confluent CF airway cells before treatment overnight with aztreonam or tobramycin alone or in combination. Alternatively, antibiotics were added 1 h after bacterial inoculation to assess their ability to impair biofilm formation at 5 h. Bacterial cfu remaining after treatment were then determined by plate counting. RESULTS In the absence of antibiotics, all strains developed biofilms that disrupted CF airway epithelial monolayers overnight. Tobramycin reduced the cfu of all strains grown as biofilms. Aztreonam reduced the cfu of some strains by ∼1 log unit without preserving the integrity of cystic fibrosis airway cell monolayers, while decreasing the biofilms of other clinical isolates by ∼4 log units and protecting the monolayers from being compromised. The combination of aztreonam and tobramycin reduced the cfu of two strains by an additional 0.5 and 2 log units, respectively. Of all the mechanisms explored, Psl exopolysaccharide production might explain the variations in biofilm tolerance to aztreonam in some of the strains. CONCLUSIONS Effects of aztreonam on P. aeruginosa biofilms in the in vitro co-culture model are strain-dependent. The simultaneous application of aztreonam and tobramycin may be beneficial for a subset of CF patients by eliminating susceptible P. aeruginosa strains.
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Affiliation(s)
- Qianru Yu
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USA
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Zeitler K, Salvas B, Stevens V, Brown J. Aztreonam lysine for inhalation: new formulation of an old antibiotic. Am J Health Syst Pharm 2012; 69:107-15. [PMID: 22215356 DOI: 10.2146/ajhp100624] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
PURPOSE The pharmacology, safety, efficacy, pharmacokinetics, pharmacodynamics, current place in therapy, and potential future therapeutic uses of inhaled aztreonam are reviewed. SUMMARY Inhaled aztreonam, a newly formulated lysine salt of the original monobactam antibiotic, is approved for the treatment of respiratory symptoms in patients with cystic fibrosis (CF) who are colonized with Pseudomonas aeruginosa. Its spectrum of activity is limited to susceptible gram-negative organisms, including P. aeruginosa. Lyophilized aztreonam lysine is diluted with 0.17% sodium chloride and administered using the Altera nebulizer system, which produces appropriate-sized particles for proper deposition in the lungs to achieve high sputum and low systemic concentrations. Mean sputum drug concentrations are highest 10 minutes after dose administration, and plasma concentrations peak one hour after inhalation. Aztreonam is excreted via active tubular secretion and glomerular filtration. Caution is advised in patients with renal or hepatic impairment, breastfeeding women, and patients age 65 years or older. Like the older i.v. formulation, inhaled aztreonam displays time-dependent killing. Phase III clinical trials have shown improvements in respiratory symptoms, decreased P. aeruginosa sputum density, prolonged time intervals between antibiotic treatments, and efficacy without the development of resistance in the face of repeated exposures. This formulation is available only from select specialty pharmacies and should only be used with the Altera nebulizer system. CONCLUSION Inhaled aztreonam has shown efficacy and safety in patients seven years of age or older with CF who have P. aeruginosa airway infections. This product may complement existing therapies and offers the advantage of a new inhaled formulation to aid in treatment regimens.
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Affiliation(s)
- Kristen Zeitler
- School of Pharmacy and Pharmaceutical Science, State University of New York at Buffalo, Buffalo, NY 14260, USA
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Han S, Caspers N, Zaniewski RP, Lacey BM, Tomaras AP, Feng X, Geoghegan KF, Shanmugasundaram V. Distinctive attributes of β-lactam target proteins in Acinetobacter baumannii relevant to development of new antibiotics. J Am Chem Soc 2011; 133:20536-45. [PMID: 22050378 DOI: 10.1021/ja208835z] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Multi-drug-resistant forms of the Gram-negative pathogen Acinetobacter baumannii are an emerging threat to human health and further complicate the general problem of treating serious bacterial infections. Meeting this challenge requires an improved understanding of the relationships between the structures of major therapeutic targets in this organism and the activity levels exhibited against it by different antibiotics. Here we report the first crystal structures of A. baumannii penicillin-binding proteins (PBPs) covalently inactivated by four β-lactam antibiotics. We also relate the results to kinetic, biophysical, and computational data. The structure of the class A protein PBP1a was solved in apo form and for its covalent conjugates with benzyl penicillin, imipenem, aztreonam, and the siderophore-conjugated monocarbam MC-1. It included a novel domain genetically spliced into a surface loop of the transpeptidase domain that contains three conserved loops. Also reported here is the first high-resolution structure of the A. baumannii class B enzyme PBP3 in apo form. Comparison of this structure with that of MC-1-derivatized PBP3 of Pseudomonas aeruginosa identified differences between these orthologous proteins in A. baumannii and P. aeruginosa. Thermodynamic analyses indicated that desolvation effects in the PBP3 ligand-binding sites contributed significantly to the thermal stability of the enzyme-antibiotic covalent complexes. Across a significant range of values, they correlated well with results from studies of inactivation kinetics and the protein structures. The structural, biophysical, and computational data help rationalize differences in the functional performance of antibiotics against different protein targets and can be used to guide the design of future agents.
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Affiliation(s)
- Seungil Han
- Pfizer Worldwide Research, Eastern Point Road, Groton, Connecticut 06340, USA.
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Kirkby S, Novak K, McCoy K. Aztreonam (for inhalation solution) for the treatment of chronic lung infections in patients with cystic fibrosis: an evidence-based review. CORE EVIDENCE 2011; 6:59-66. [PMID: 22022288 PMCID: PMC3195667 DOI: 10.2147/ce.s11181] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Indexed: 12/04/2022]
Abstract
Cystic fibrosis (CF) is a genetic disease caused by abnormal chloride transport across cellular membranes. In the respiratory tract, this molecular defect causes obstruction of the airways by mucus and chronic endobronchial infection. The majority of patients suffer early death from chronic respiratory disease. Pseudomonas aeruginosa is the predominant chronic airway pathogen in older children and adults with CF and is associated with worse outcomes. However, overall survival in CF has been greatly improved in recent decades due in large part to the aggressive treatment of chronic infections such as P. aeruginosa. While intravenous and oral antibiotics are commonly used in the management of CF respiratory infections, inhaled anti-infective therapies offer the benefit of delivering the drug directly to the site of infection and avoiding potential toxicities associated with systemic absorption. Aztreonam lysine (AZLI) has recently been developed as an inhaled antibiotic for chronic use in CF patients with endobronchial P. aeruginosa infection. This paper reviews background data and the clinical studies which contributed to AZLI’s formal FDA approval and growing role in the management of CF pulmonary disease.
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Affiliation(s)
- Stephen Kirkby
- Section of Pulmonary Medicine, Nationwide Children's Hospital
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Novel genetic environment of the plasmid-mediated KPC-3 gene detected in Escherichia coli and Citrobacter freundii isolates from China. Eur J Clin Microbiol Infect Dis 2010; 30:575-80. [PMID: 21153909 PMCID: PMC3052496 DOI: 10.1007/s10096-010-1124-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 11/20/2010] [Indexed: 11/09/2022]
Abstract
The imipenem and meropenem-resistant strains Citrobacter freundii HS70 and Escherichia coli HS510 were isolated from patients in Shanghai, China. By isoelectric focusing, PCR amplification and sequencing, these strains were each found to produce four β-lactamases: TEM-1, KPC-3, SHV-7 and CTX-M-14. A conjugation experiment and plasmid restriction digestion revealed that the blaKPC-3 gene was located on the same plasmid in both isolates. Bidirectional primer walking sequencing showed that the nucleotide sequence surrounding the 3.8 kb blaKPC-3 contained a 671-bp insertion similar to that previously characterized in China. The insertion was located between the promoter and the coding region of the blaKPC-3 gene. Susceptibility testing performed on recombinant strains carrying the blaKPC-3 gene with or without the insertion revealed that minimum inhibitory concentrations of imipenem, meropenem, cefepime, and cefotaxime for E. coli EMU-KPC3 (without insertion) were four times higher than that of E. coli EKPC3 (with insertion). The 671 bp insertion reduced blaKPC-3 expression significantly. Taken together, these results suggest that KPC-3-producing C. freundii and E. coli have begun to emerge in our hospital.
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Structural basis for effectiveness of siderophore-conjugated monocarbams against clinically relevant strains of Pseudomonas aeruginosa. Proc Natl Acad Sci U S A 2010; 107:22002-7. [PMID: 21135211 DOI: 10.1073/pnas.1013092107] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen that causes nosocomial infections for which there are limited treatment options. Penicillin-binding protein PBP3, a key therapeutic target, is an essential enzyme responsible for the final steps of peptidoglycan synthesis and is covalently inactivated by β-lactam antibiotics. Here we disclose the first high resolution cocrystal structures of the P. aeruginosa PBP3 with both novel and marketed β-lactams. These structures reveal a conformational rearrangement of Tyr532 and Phe533 and a ligand-induced conformational change of Tyr409 and Arg489. The well-known affinity of the monobactam aztreonam for P. aeruginosa PBP3 is due to a distinct hydrophobic aromatic wall composed of Tyr503, Tyr532, and Phe533 interacting with the gem-dimethyl group. The structure of MC-1, a new siderophore-conjugated monocarbam complexed with PBP3 provides molecular insights for lead optimization. Importantly, we have identified a novel conformation that is distinct to the high-molecular-weight class B PBP subfamily, which is identifiable by common features such as a hydrophobic aromatic wall formed by Tyr503, Tyr532, and Phe533 and the structural flexibility of Tyr409 flanked by two glycine residues. This is also the first example of a siderophore-conjugated triazolone-linked monocarbam complexed with any PBP. Energetic analysis of tightly and loosely held computed hydration sites indicates protein desolvation effects contribute significantly to PBP3 binding, and analysis of hydration site energies allows rank ordering of the second-order acylation rate constants. Taken together, these structural, biochemical, and computational studies provide a molecular basis for recognition of P. aeruginosa PBP3 and open avenues for future design of inhibitors of this class of PBPs.
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Xie L, Xu M, Yang T, Zhu C, Zhu B, Hu Y. Studies on amino acid replacement and inhibitory activity of a beta-lactamase inhibitory peptide. BIOCHEMISTRY (MOSCOW) 2010; 75:336-41. [PMID: 20370612 DOI: 10.1134/s0006297910030107] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An SHV beta-lactamase gene was amplified from a beta-lactam resistant Klebsiella pneumoniae K-71 genomic DNA. After expression and purification, we demonstrated that peptide P1 could inhibit the hydrolysis activity of both TEM-1 and SHV beta-lactamase in vitro. Three mutations were introduced into P1 in which the first residue S was replaced by F, the 18th residue V was mutated to Y, and the 15th residue Y was substituted with A, C, G, and R to obtain the mutants of P1-A, P1-C, P1-G, and P1-R, respectively. The mutant peptides were purified and their inhibitory constants against TEM-1 and SHV beta-lactamase were determined. All these beta-lactamase inhibitory peptides could inhibit the activity of both beta-lactamases, while the mutant peptides showed stronger inhibitory activities against TEM-1 beta-lactamase than against SHV beta-lactamase. Inhibition data suggested that P1-A improved the beta-lactamase inhibitory activity by over 3-fold compare to P1. When P1-A was incubated with K. pneumoniae K-71 in Luria-Bertani medium containing ampicillin, it showed a much stronger growth of inhibition ratio over P1. This study gives us a good candidate for development of novel beta-lactamase inhibitors.
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Affiliation(s)
- Liping Xie
- State Key Laboratory of New Drug and Pharmaceutical Process, Shanghai Institute of Pharmaceutical Industry, Shanghai, China
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Abstract
In February 2010, aztreonam for inhalation solution (Cayston; Gilead) - an inhalable formulation of the monobactam antibiotic aztreonam and lysine - was approved by the US FDA to improve respiratory symptoms in patients with cystic fibrosis infected with Pseudomonas aeruginosa.
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Abstract
Since the introduction of penicillin, beta-lactam antibiotics have been the antimicrobial agents of choice. Unfortunately, the efficacy of these life-saving antibiotics is significantly threatened by bacterial beta-lactamases. beta-Lactamases are now responsible for resistance to penicillins, extended-spectrum cephalosporins, monobactams, and carbapenems. In order to overcome beta-lactamase-mediated resistance, beta-lactamase inhibitors (clavulanate, sulbactam, and tazobactam) were introduced into clinical practice. These inhibitors greatly enhance the efficacy of their partner beta-lactams (amoxicillin, ampicillin, piperacillin, and ticarcillin) in the treatment of serious Enterobacteriaceae and penicillin-resistant staphylococcal infections. However, selective pressure from excess antibiotic use accelerated the emergence of resistance to beta-lactam-beta-lactamase inhibitor combinations. Furthermore, the prevalence of clinically relevant beta-lactamases from other classes that are resistant to inhibition is rapidly increasing. There is an urgent need for effective inhibitors that can restore the activity of beta-lactams. Here, we review the catalytic mechanisms of each beta-lactamase class. We then discuss approaches for circumventing beta-lactamase-mediated resistance, including properties and characteristics of mechanism-based inactivators. We next highlight the mechanisms of action and salient clinical and microbiological features of beta-lactamase inhibitors. We also emphasize their therapeutic applications. We close by focusing on novel compounds and the chemical features of these agents that may contribute to a "second generation" of inhibitors. The goal for the next 3 decades will be to design inhibitors that will be effective for more than a single class of beta-lactamases.
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Affiliation(s)
- Sarah M. Drawz
- Departments of Pathology, Medicine, Pharmacology, Molecular Biology and Microbiology, Case Western Reserve University School of Medicine, Cleveland, Ohio, Research Service, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, Ohio
| | - Robert A. Bonomo
- Departments of Pathology, Medicine, Pharmacology, Molecular Biology and Microbiology, Case Western Reserve University School of Medicine, Cleveland, Ohio, Research Service, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, Ohio
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Hydrolysis and inhibition profiles of beta-lactamases from molecular classes A to D with doripenem, imipenem, and meropenem. Antimicrob Agents Chemother 2009; 54:565-9. [PMID: 19884379 DOI: 10.1128/aac.01004-09] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The stability of doripenem to hydrolysis by beta-lactamases from molecular classes A to D was compared to the stability for imipenem and meropenem. Doripenem was stable to hydrolysis by extended-spectrum beta-lactamases and AmpC type beta-lactamases and demonstrated high affinity for the AmpC enzymes. For the serine carbapenemases SME-3 and KPC-2 and metallo-beta-lactamases IMP-1 and VIM-2, doripenem hydrolysis was generally 2- to 150-fold slower than imipenem hydrolysis. SPM-1 hydrolyzed meropenem and doripenem fourfold faster than imipenem.
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Abstract
523 blood culture isolates collected during 18 months (July 1980-December 1981) were analysed by the agar dilution method for sensitivity to 33 antibiotics. Breakpoints corresponding to the SIR system were used but for N-formimidoyl-thienamycin (N-f-thienamycin), azthreonam and fosfomycin serial dilutions were made. Aminoglycosides (netilmicin, gentamicin, amikacin and tobramycin) inhibited from 90 to 86% of the strains. This was comparable to the percentage inhibited by some cephalosporins (cefotaxime, cefoperazone, ceftazidime, ceftriaxone, cefuroxime, cephamandole and moxalactam) ranging from 95 to 89%. A very high number of strains (99%) were inhibited by N-f-thienamycin. By combination of certain antibiotics more than 99% of the strains could be inhibited.
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Characterization of the new metallo-beta-lactamase VIM-13 and its integron-borne gene from a Pseudomonas aeruginosa clinical isolate in Spain. Antimicrob Agents Chemother 2008; 52:3589-96. [PMID: 18644957 DOI: 10.1128/aac.00465-08] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During a survey conducted to evaluate the incidence of class B carbapenemase (metallo-beta-lactamase [MBL])-producing Pseudomonas aeruginosa strains from hospitals in Majorca, Spain, five clinical isolates showed a positive Etest MBL screening test result. In one of them, strain PA-SL2, the presence of a new bla(VIM) derivative (bla(VIM-13)) was detected by PCR amplification with bla(VIM-1)-specific primers followed by sequencing. The bla(VIM-13)-producing isolate showed resistance to all beta-lactams (except aztreonam), gentamicin, tobramycin, and ciprofloxacin. VIM-13 exhibited 93% and 88% amino acid sequence identities with VIM-1 and VIM-2, respectively. bla(VIM-13) was cloned in parallel with bla(VIM-1), and the resistance profile conferred was analyzed both in Escherichia coli and in P. aeruginosa backgrounds. Compared to VIM-1, VIM-13 conferred slightly higher levels of resistance to piperacillin and lower levels of resistance to ceftazidime and cefepime. VIM-13 and VIM-1 were purified in parallel as well, and their kinetic parameters were compared. The k(cat)/K(m) ratios for the antibiotics mentioned above were in good agreement with the MIC data. Furthermore, EDTA inhibited the activity of VIM-13 approximately 25 times less than it inhibited the activity of VIM-1. VIM-13 was harbored in a class 1 integron, along with a new variant (Ala108Thr) of the aminoglycoside-modifying enzyme encoding gene aacA4, which confers resistance to gentamicin and tobramycin. Finally, the VIM-13 integron was apparently located in the chromosome, since transformation and conjugation experiments consistently yielded negative results and the bla(VIM-13) probe hybridized only with the genomic DNA.
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