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Ramakrishnan G, Chandra NR, Srinivasan N. Recognizing drug targets using evolutionary information: implications for repurposing FDA-approved drugs against Mycobacterium tuberculosis H37Rv. MOLECULAR BIOSYSTEMS 2016; 11:3316-31. [PMID: 26429199 DOI: 10.1039/c5mb00476d] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Drug repurposing to explore target space has been gaining pace over the past decade with the upsurge in the use of systematic approaches for computational drug discovery. Such a cost and time-saving approach gains immense importance for pathogens of special interest, such as Mycobacterium tuberculosis H37Rv. We report a comprehensive approach to repurpose drugs, based on the exploration of evolutionary relationships inferred from the comparative sequence and structural analyses between targets of FDA-approved drugs and the proteins of M. tuberculosis. This approach has facilitated the identification of several polypharmacological drugs that could potentially target unexploited M. tuberculosis proteins. A total of 130 FDA-approved drugs, originally intended against other diseases, could be repurposed against 78 potential targets in M. tuberculosis. Additionally, we have also made an attempt to augment the chemical space by recognizing compounds structurally similar to FDA-approved drugs. For three of the attractive cases we have investigated the probable binding modes of the drugs in their corresponding M. tuberculosis targets by means of structural modelling. Such prospective targets and small molecules could be prioritized for experimental endeavours, and could significantly influence drug-discovery and drug-development programmes for tuberculosis.
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Affiliation(s)
- Gayatri Ramakrishnan
- Indian Institute of Science Mathematics Initiative, Indian Institute of Science, Bangalore-560012, India and Molecular Biophysics Unit, Indian Institute of Science, Bangalore-560012, India.
| | - Nagasuma R Chandra
- Department of Biochemistry, Indian Institute of Science, Bangalore-560012, India
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Ghimire S, van't Boveneind-Vrubleuskaya N, Akkerman OW, de Lange WCM, van Soolingen D, Kosterink JGW, van der Werf TS, Wilffert B, Touw DJ, Alffenaar JWC. Pharmacokinetic/pharmacodynamic-based optimization of levofloxacin administration in the treatment of MDR-TB. J Antimicrob Chemother 2016; 71:2691-703. [DOI: 10.1093/jac/dkw164] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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Alsultan A, An G, Peloquin CA. Limited sampling strategy and target attainment analysis for levofloxacin in patients with tuberculosis. Antimicrob Agents Chemother 2015; 59:3800-7. [PMID: 25870068 PMCID: PMC4468713 DOI: 10.1128/aac.00341-15] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 04/05/2015] [Indexed: 11/20/2022] Open
Abstract
There is an urgent need to improve and shorten the treatment of tuberculosis (TB) and multidrug resistant tuberculosis (MDR-TB). Levofloxacin, a newer fluoroquinolone, has potent activity against TB both in vitro and in vivo. Levofloxacin dosing can be optimized to improve the treatment of both TB and MDR-TB. Levofloxacin efficacy is linked primarily to the ratio of the area under the concentration-time curve for the free fraction of drug (fAUC) to the MIC. Since obtaining a full-time concentration profile is not feasible in the clinic, we developed a limited sampling strategy (LSS) to estimate the AUC. We also utilized Monte Carlo simulations to evaluate the dosing of levofloxacin. Pharmacokinetic data were obtained from 10 Brazilian TB patients. The pharmacokinetic data were fitted with a one-compartment model. LSSs were developed using two methods: linear regression and Bayesian approaches. Several LSSs predicted levofloxacin AUC with good accuracy and precision. The most accurate were the method using two samples collected at 4 and 6 h (R(2) = 0.91 using linear regression and 0.97 using Bayesian approaches) and that using samples collected at 2 and 6 h (R(2) = 0.90 using linear regression and 0.96 using Bayesian approaches). The 2-and-6-h approach also provides a good estimate of the maximum concentration of the drug in serum (Cmax). Our target attainment analysis showed that higher doses (17 to 20 mg/kg of body weight) of levofloxacin might be needed to improve its activity. Doses in the range of 17 to 20 mg/kg showed good target attainment for MICs from 0.25 to 0.50. At an MIC of 2, poor target attainment was observed across all doses. This LSS for levofloxacin can be used for therapeutic drug monitoring and for future pharmacokinetic/pharmacodynamic studies.
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Affiliation(s)
- Abdullah Alsultan
- University of Florida, College of Pharmacy, Department of Pharmacotherapy and Translational Research, and the Emerging Pathogens Institute, Gainesville, Florida, USA
| | - Guohua An
- University of Iowa, College of Pharmacy, Division of Pharmaceutics and Translational Therapeutics, Iowa City, Iowa, USA
| | - Charles A Peloquin
- University of Florida, College of Pharmacy, Department of Pharmacotherapy and Translational Research, and the Emerging Pathogens Institute, Gainesville, Florida, USA
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Targeting Mycobacterium tuberculosis topoisomerase I by small-molecule inhibitors. Antimicrob Agents Chemother 2014; 59:1549-57. [PMID: 25534741 DOI: 10.1128/aac.04516-14] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
We describe inhibition of Mycobacterium tuberculosis topoisomerase I (MttopoI), an essential mycobacterial enzyme, by two related compounds, imipramine and norclomipramine, of which imipramine is clinically used as an antidepressant. These molecules showed growth inhibition of both Mycobacterium smegmatis and M. tuberculosis cells. The mechanism of action of these two molecules was investigated by analyzing the individual steps of the topoisomerase I (topoI) reaction cycle. The compounds stimulated cleavage, thereby perturbing the cleavage-religation equilibrium. Consequently, these molecules inhibited the growth of the cells overexpressing topoI at a low MIC. Docking of the molecules on the MttopoI model suggested that they bind near the metal binding site of the enzyme. The DNA relaxation activity of the metal binding mutants harboring mutations in the DxDxE motif was differentially affected by the molecules, suggesting that the metal coordinating residues contribute to the interaction of the enzyme with the drug. Taken together, the results highlight the potential of these small molecules, which poison the M. tuberculosis and M. smegmatis topoisomerase I, as leads for the development of improved molecules to combat mycobacterial infections. Moreover, targeting metal coordination in topoisomerases might be a general strategy to develop new lead molecules.
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Mustaev A, Malik M, Zhao X, Kurepina N, Luan G, Oppegard LM, Hiasa H, Marks KR, Kerns RJ, Berger JM, Drlica K. Fluoroquinolone-gyrase-DNA complexes: two modes of drug binding. J Biol Chem 2014; 289:12300-12. [PMID: 24497635 DOI: 10.1074/jbc.m113.529164] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
DNA gyrase and topoisomerase IV control bacterial DNA topology by breaking DNA, passing duplex DNA through the break, and then resealing the break. This process is subject to reversible corruption by fluoroquinolones, antibacterials that form drug-enzyme-DNA complexes in which the DNA is broken. The complexes, called cleaved complexes because of the presence of DNA breaks, have been crystallized and found to have the fluoroquinolone C-7 ring system facing the GyrB/ParE subunits. As expected from x-ray crystallography, a thiol-reactive, C-7-modified chloroacetyl derivative of ciprofloxacin (Cip-AcCl) formed cross-linked cleaved complexes with mutant GyrB-Cys(466) gyrase as evidenced by resistance to reversal by both EDTA and thermal treatments. Surprisingly, cross-linking was also readily seen with complexes formed by mutant GyrA-G81C gyrase, thereby revealing a novel drug-gyrase interaction not observed in crystal structures. The cross-link between fluoroquinolone and GyrA-G81C gyrase correlated with exceptional bacteriostatic activity for Cip-AcCl with a quinolone-resistant GyrA-G81C variant of Escherichia coli and its Mycobacterium smegmatis equivalent (GyrA-G89C). Cip-AcCl-mediated, irreversible inhibition of DNA replication provided further evidence for a GyrA-drug cross-link. Collectively these data establish the existence of interactions between the fluoroquinolone C-7 ring and both GyrA and GyrB. Because the GyrA-Gly(81) and GyrB-Glu(466) residues are far apart (17 Å) in the crystal structure of cleaved complexes, two modes of quinolone binding must exist. The presence of two binding modes raises the possibility that multiple quinolone-enzyme-DNA complexes can form, a discovery that opens new avenues for exploring and exploiting relationships between drug structure and activity with type II DNA topoisomerases.
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Affiliation(s)
- Arkady Mustaev
- From the Public Health Research Institute and Department of Microbiology and Molecular Genetics, New Jersey Medical School, Rutgers Biomedical and Health Sciences, Newark, New Jersey 07103
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Maruri F, Sterling TR, Kaiga AW, Blackman A, van der Heijden YF, Mayer C, Cambau E, Aubry A. A systematic review of gyrase mutations associated with fluoroquinolone-resistant Mycobacterium tuberculosis and a proposed gyrase numbering system. J Antimicrob Chemother 2012; 67:819-31. [PMID: 22279180 PMCID: PMC3299416 DOI: 10.1093/jac/dkr566] [Citation(s) in RCA: 174] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Revised: 11/28/2011] [Accepted: 12/07/2011] [Indexed: 11/14/2022] Open
Abstract
Fluoroquinolone resistance in Mycobacterium tuberculosis has become increasingly important. A review of mutations in DNA gyrase, the fluoroquinolone target, is needed to improve the molecular detection of resistance. We performed a systematic review of studies reporting mutations in DNA gyrase genes in clinical M. tuberculosis isolates. From 42 studies that met inclusion criteria, 1220 fluoroquinolone-resistant M. tuberculosis isolates underwent sequencing of the quinolone resistance-determining region (QRDR) of gyrA; 780 (64%) had mutations. The QRDR of gyrB was sequenced in 534 resistant isolates; 17 (3%) had mutations. Mutations at gyrA codons 90, 91 or 94 were present in 654/1220 (54%) resistant isolates. Four different GyrB numbering systems were reported, resulting in mutation location discrepancies. We propose a consensus numbering system. Most fluoroquinolone-resistant M. tuberculosis isolates had mutations in DNA gyrase, but a substantial proportion did not. The proposed consensus numbering system can improve molecular detection of resistance and identification of novel mutations.
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Affiliation(s)
- Fernanda Maruri
- Division of Infectious Diseases, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Timothy R. Sterling
- Division of Infectious Diseases, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA
- Center for Health Services Research, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Anne W. Kaiga
- Department of Epidemiology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Amondrea Blackman
- Division of Infectious Diseases, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Yuri F. van der Heijden
- Division of Infectious Diseases, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Claudine Mayer
- Unité de Dynamique Structurale des Macromolécules, Département de Biologie Structurale et Chimie, Institut Pasteur, Paris, France
- URA 2185, Centre National de la Recherche Scientifique (CNRS), Paris, France
- Université Paris Diderot-Paris 07, EA3964, Paris, France
| | - Emmanuelle Cambau
- Université Paris Diderot-Paris 07, EA3964, Paris, France
- Centre National de Référence des Mycobactéries et de la Résistance des Mycobactéries aux Antituberculeux, F-75013 Paris, France
- Assistance Publique Hôpitaux de Paris, Groupe Hospitalier Saint Louis-Lariboisière-Fernand Widal, Paris, France
| | - Alexandra Aubry
- Centre National de Référence des Mycobactéries et de la Résistance des Mycobactéries aux Antituberculeux, F-75013 Paris, France
- Pierre et Marie Curie Université Paris 06, EA1541, Bactériologie-Hygiène, Paris, France
- Assistance Publique Hôpitaux de Paris, Groupe Hospitalier Pitié-Salpêtrière, Paris, France
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High-resolution melting analysis for the rapid detection of fluoroquinolone and streptomycin resistance in Mycobacterium tuberculosis. PLoS One 2012; 7:e31934. [PMID: 22363772 PMCID: PMC3283711 DOI: 10.1371/journal.pone.0031934] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Accepted: 01/18/2012] [Indexed: 01/13/2023] Open
Abstract
Background Molecular methods for the detection of drug-resistant tuberculosis are potentially more rapid than conventional culture-based drug susceptibility testing, facilitating the commencement of appropriate treatment for patients with drug resistant tuberculosis. We aimed to develop and evaluate high-resolution melting (HRM) assays for the detection of mutations within gyrA, rpsL, and rrs, for the determination of fluoroquinolone and streptomycin resistance in Mycobacterium tuberculosis (MTB). Methodology/Principal Findings A blinded series of DNA samples extracted from a total of 92 clinical isolates of MTB were analyzed by HRM analysis, and the results were verified using DNA sequencing. The sensitivity and specificity of the HRM assays in comparison with drug susceptibility testing were 74.1% and 100.0% for the detection of fluoroquinolone resistance, and 87.5% and 100.0% for streptomycin resistance. Five isolates with low level resistance to ofloxacin had no mutations detected in gyrA, possibly due to the action of efflux pumps, or false negativity due to mixed infections. One fluoroquinolone-resistant isolate had a mutation in a region of gyrA not encompassed by our assay. Six streptomycin-resistant strains had undetectable mutations by HRM and DNA sequencing, which may be explained by the fact that not all streptomycin-resistant isolates have mutations within rpsL and rrs, and suggesting that other targets may be involved. Conclusion The HRM assays described here are potentially useful adjunct tests for the efficient determination of fluoroquinolone and streptomycin resistance in MTB, and could facilitate the timely administration of appropriate treatment for patients infected with drug-resistant TB.
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Maganti L, Das SK, Mascarenhas NM, Ghoshal N. Deciphering the Structural Requirements of Nucleoside Bisubstrate Analogues for Inhibition of MbtA in Mycobacterium tuberculosis: A FB-QSAR Study and Combinatorial Library Generation for Identifying Potential Hits. Mol Inform 2011; 30:863-72. [DOI: 10.1002/minf.201100056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Accepted: 07/05/2011] [Indexed: 11/06/2022]
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Soudani A, Hadjfredj S, Zribi M, Messaoud T, Masmoudi A, Majed B, Fendri C. First report of molecular characterization of fluoroquinolone-resistant Mycobacterium tuberculosis isolates from a Tunisian hospital. Clin Microbiol Infect 2010. [DOI: 10.1111/j.1469-0691.2010.03087.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Mutant selection window and characterization of allelic diversity for ciprofloxacin-resistant mutants of Rhodococcus equi. Antimicrob Agents Chemother 2010; 54:3520-3. [PMID: 20498313 DOI: 10.1128/aac.01670-09] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mutant prevention concentration (MPC) for ciprofloxacin was determined for two Rhodococcus equi strains. The MPC for both strains was 32 mug/ml, which is above the peak serum concentration of ciprofloxacin obtainable by oral administration in humans. Nine single nucleotide changes corresponding to eight amino acid substitutions in the quinolone resistance-determining regions of DNA gyrase subunits A and B were characterized. Only mutants with amino acid changes in Ser-83 of GyrA were highly resistant (>or=64 microg/ml). Our results suggest that ciprofloxacin monotherapy against R. equi infection may result in the emergence of ciprofloxacin-resistant mutants.
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Kumar A, Siddiqi MI. CoMFA based de novo design of Pyrrolidine Carboxamides as Inhibitors of Enoyl Acyl Carrier Protein Reductase from Mycobacterium tuberculosis. J Mol Model 2008; 14:923-35. [DOI: 10.1007/s00894-008-0326-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Accepted: 05/29/2008] [Indexed: 11/29/2022]
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Minimising moxifloxacin resistance with tuberculosis. THE LANCET. INFECTIOUS DISEASES 2008; 8:273-5. [DOI: 10.1016/s1473-3099(08)70077-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Singh N, Avery MA, McCurdy CR. Toward Mycobacterium tuberculosis DXR inhibitor design: homology modeling and molecular dynamics simulations. J Comput Aided Mol Des 2007; 21:511-22. [PMID: 17874041 DOI: 10.1007/s10822-007-9132-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2007] [Accepted: 08/28/2007] [Indexed: 10/22/2022]
Abstract
Mycobacterium tuberculosis 1-deoxy-D: -xylulose-5-phosphate reductoisomerase (MtDXR) is a potential target for antitubercular chemotherapy. In the absence of its crystallographic structure, our aim was to develop a structural model of MtDXR. This will allow us to gain early insight into the structure and function of the enzyme and its likely binding to ligands and cofactors and thus, facilitate structure-based inhibitor design. To achieve this goal, initial models of MtDXR were generated using MODELER. The best quality model was refined using a series of minimizations and molecular dynamics simulations. A protein-ligand complex was also developed from the initial homology model of the target protein by including information about the known ligand as spatial restraints and optimizing the mutual interactions between the ligand and the binding site. The final model was evaluated on the basis of its ability to explain several site-directed mutagenesis data. Furthermore, a comparison of the homology model with the X-ray structure published in the final stages of the project shows excellent agreement and validates the approach. The knowledge gained from the current study should prove useful in the design and development of inhibitors as potential novel therapeutic agents against tuberculosis by either de novo drug design or virtual screening of large chemical databases.
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Affiliation(s)
- Nidhi Singh
- Department of Medicinal Chemistry, Laboratory for Applied Drug Design and Synthesis, University of Mississippi, University, MS, 38677-1848, USA
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Goessens WHF, Mouton JW, ten Kate MT, Bijl AJ, Ott A, Bakker-Woudenberg IAJM. Role of ceftazidime dose regimen on the selection of resistant Enterobacter cloacae in the intestinal flora of rats treated for an experimental pulmonary infection. J Antimicrob Chemother 2007; 59:507-16. [PMID: 17289765 DOI: 10.1093/jac/dkl529] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES The effect of ceftazidime dosing increments and frequency of dosing on the selection of ceftazidime-resistant Enterobacter cloacae in the intestine was studied in rats, during treatment of a pulmonary infection caused by Klebsiella pneumoniae. METHODS Rats with pulmonary infection (n = 10 per group) received therapy with doses of ceftazidime at 3.1 to 400 mg/kg per day at a frequency of every 6,12 or 24 h for 18 days, starting 24 h after bacterial inoculation of the lung. Emergence of resistance in intestinal E. cloacae was monitored by culturing fresh stool specimens at days 0, 8, 15, 22, 29, 36 and 43 on agar plates with (6.4 mg/L) and without ceftazidime. Pharmacodynamic indices and time within the mutant selection window (MSW) were assessed in infected rats for each regimen. Ceftazidime-resistant E. cloacae mutants were characterized by determination of the beta-lactamase activity under cefoxitin-induced and non-induced conditions. RESULTS A reduction of intestinal ceftazidime-susceptible E. cloacae was observed and showed a significant correlation with the fAUC/MIC at days 8, 15 and 22 and with the fCmax on days 8, 15, 22, 29 and 36. More rats treated with 12-25 and 50-100 mg/kg per day every 6 h were found colonized with ceftazidime-resistant E. cloacae mutants than animals treated every 12 h or every 24 h. The proportion of rats colonized with ceftazidime-resistant E. cloacae mutants at days 15, 36 and 43 correlated with the time during which ceftazidime plasma concentrations were within the boundaries of the MSW. Only at day 15 was a correlation demonstrated between the fCmax and significantly fewer rats colonized with ceftazidime-resistant E. cloacae. Ceftazidime-resistant E. cloacae mutants (MIC >or= 128 mg/L) were characterized as stable derepressed mutants. CONCLUSIONS Colonization with stable derepressed ceftazidime-resistant E. cloacae mutants particularly occurred when rats were exposed to moderate doses of ceftazidime (12-25 or 50-100 mg/kg per day) administered every 6 h. Emergence of resistance was correlated with time within the MSW.
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Affiliation(s)
- W H F Goessens
- Department of Medical Microbiology & Infectious Diseases, Erasmus University Medical Center Rotterdam, Rotterdam, The Netherlands.
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Matrat S, Veziris N, Mayer C, Jarlier V, Truffot-Pernot C, Camuset J, Bouvet E, Cambau E, Aubry A. Functional analysis of DNA gyrase mutant enzymes carrying mutations at position 88 in the A subunit found in clinical strains of Mycobacterium tuberculosis resistant to fluoroquinolones. Antimicrob Agents Chemother 2006; 50:4170-3. [PMID: 17015625 PMCID: PMC1694005 DOI: 10.1128/aac.00944-06] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We investigated the enzymatic efficiency and inhibition by quinolones of Mycobacterium tuberculosis DNA gyrases carrying the previously described GyrA G88C mutation and the novel GyrA G88A mutation harbored by two multidrug-resistant clinical strains and reproduced by site-directed mutagenesis. Fluoroquinolone MICs and 50% inhibitory concentrations for both mutants were 2- to 43-fold higher than for the wild type, demonstrating that these mutations confer fluoroquinolone resistance in M. tuberculosis.
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Affiliation(s)
- Stéphanie Matrat
- Laboratoire de Bactériologie, Centre National de Référence des Mycobactéries et de la Résistance des Mycobactéries aux Antituberculeux, site Pitié-Salpêtrière, Université Paris 6, Assistance Publique-Hôpitaux de Paris, Paris, France
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Sullivan TJ, Truglio JJ, Boyne ME, Novichenok P, Zhang X, Stratton CF, Li HJ, Kaur T, Amin A, Johnson F, Slayden RA, Kisker C, Tonge PJ. High affinity InhA inhibitors with activity against drug-resistant strains of Mycobacterium tuberculosis. ACS Chem Biol 2006; 1:43-53. [PMID: 17163639 DOI: 10.1021/cb0500042] [Citation(s) in RCA: 182] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Novel chemotherapeutics for treating multidrug-resistant (MDR) strains of Mycobacterium tuberculosis (MTB) are required to combat the spread of tuberculosis, a disease that kills more than 2 million people annually. Using structure-based drug design, we have developed a series of alkyl diphenyl ethers that are uncompetitive inhibitors of InhA, the enoyl reductase enzyme in the MTB fatty acid biosynthesis pathway. The most potent compound has a Ki' value of 1 nM for InhA and MIC99 values of 2-3 microg mL(-1) (6-10 microM) for both drug-sensitive and drug-resistant strains of MTB. Overexpression of InhA in MTB results in a 9-12-fold increase in MIC99, consistent with the belief that these compounds target InhA within the cell. In addition, transcriptional response studies reveal that the alkyl diphenyl ethers fail to upregulate a putative efflux pump and aromatic dioxygenase, detoxification mechanisms that are triggered by the lead compound triclosan. These diphenyl ether-based InhA inhibitors do not require activation by the mycobacterial KatG enzyme, thereby circumventing the normal mechanism of resistance to the front line drug isoniazid (INH) and thus accounting for their activity against INH-resistant strains of MTB.
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Affiliation(s)
- Todd J Sullivan
- Department of Chemistry, SUNY Stony Brook, Stony Brook, New York 11794-3400, USA
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Wehbeh W, Rojas-Diaz R, Li X, Mariano N, Grenner L, Segal-Maurer S, Tommasulo B, Drlica K, Urban C, Rahal JJ. Fluoroquinolone-resistant Streptococcus agalactiae: epidemiology and mechanism of resistance. Antimicrob Agents Chemother 2005; 49:2495-7. [PMID: 15917553 PMCID: PMC1140524 DOI: 10.1128/aac.49.6.2495-2497.2005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Quinolone-resistant Streptococcus agalactiae bacteria were recovered from single-patient isolates and found to contain mutations in the gyrase and topoisomerase IV genes. Pulsed-field gel electrophoresis demonstrated that four isolates from the same long-term care facility were closely related; in seven cases, quinolone-resistant Haemophilus influenzae and S. agalactiae bacteria were isolated from the same patient.
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Affiliation(s)
- Wehbeh Wehbeh
- Infectious Disease Section, Department of Medicine and Lang Research Center, New York Hospital Queens, 56-45 Main Street, Flushing, NY 11355, USA.
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Giannoni F, Iona E, Sementilli F, Brunori L, Pardini M, Migliori GB, Orefici G, Fattorini L. Evaluation of a new line probe assay for rapid identification of gyrA mutations in Mycobacterium tuberculosis. Antimicrob Agents Chemother 2005; 49:2928-33. [PMID: 15980370 PMCID: PMC1168684 DOI: 10.1128/aac.49.7.2928-2933.2005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2004] [Revised: 01/21/2005] [Accepted: 03/03/2005] [Indexed: 11/20/2022] Open
Abstract
Resistance of Mycobacterium tuberculosis to fluoroquinolones (FQ) results mostly from mutations in the gyrA gene. We developed a reverse hybridization-based line probe assay in which oligonucleotide probes carrying the wild-type gyrA sequence, a serine-to-threonine (S95T) polymorphism, and gyrA mutations (A90V, A90V-S95T, S91P, S91P-S95T, D94A, D94N, D94G-S95T, D94H-S95T) were immobilized on nitrocellulose strips and hybridized with digoxigenin-labeled PCR products obtained from M. tuberculosis strains. When a mutated PCR product was used, hybridization occurred to the corresponding mutated probe but not to the wild-type probe. A panel of M. tuberculosis complex strains including 19 ofloxacin-resistant (OFL-R) and 9 ofloxacin-susceptible (OFL-S) M. tuberculosis strains was studied for detection and identification of gyrA mutations by the line probe assay and nucleotide sequencing, in comparison with testing of in vitro susceptibility to FQ. Results were 100% concordant with those of nucleotide sequencing. The S95T polymorphism, which is not related to FQ resistance, was found in 5 OFL-S and 2 OFL-R strains; the other 17 OFL-R strains harbored single mutations associated with serine or threonine at codon 95. No mutations were found in the other OFL-S strains. Overall, on the basis of the MICs on solid medium, the new line probe assay correctly identified all OFL-S and 17 out of 19 (89.5%) OFL-R strains. A nested-PCR protocol was also evaluated for the assay to amplify PCR products from M. tuberculosis-spiked sputa, with a good specificity and a sensitivity of 2 x 10(3) M. tuberculosis CFU per ml of sputum.
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Affiliation(s)
- Federico Giannoni
- Dipartimento di Malattie Infettive, Parassitarie e Immunomediate, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
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Bozeman L, Burman W, Metchock B, Welch L, Weiner M. Fluoroquinolone Susceptibility among Mycobacterium tuberculosis Isolates from the United States and Canada. Clin Infect Dis 2005; 40:386-91. [PMID: 15668861 DOI: 10.1086/427292] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2004] [Accepted: 09/22/2004] [Indexed: 11/03/2022] Open
Abstract
BACKGROUND There is increasing interest in the possible role of new fluoroquinolone antibiotics for treatment of tuberculosis, but widespread use of fluoroquinolones for treatment of other bacterial infections may select for resistant strains of Mycobacterium tuberculosis. METHODS We evaluated fluoroquinolone susceptibility using the proportion method (critical ciprofloxacin concentration for susceptibility testing, 2.0 mu g/mL) in isolates obtained from patients enrolled in Tuberculosis Trial Consortium clinical trials during the period of 1995-2001 and in a referral sample of isolates sent to the Centers for Disease Control and Prevention (Atlanta, GA) during the period of 1996-2000 for additional testing, often because of drug resistance. RESULTS Of the 1373 isolates from the clinical trials, 1324 (96%) were susceptible to isoniazid and rifampin; 2 (0.15%) of these isolates were also resistant to ciprofloxacin. Of the 1852 isolates from the referral sample, 603 (32.6%) were resistant to isoniazid and rifampin (i.e., multidrug resistant), 849 (45.7%) were resistant to >or=1 first-line drug but were not resistant to both isoniazid and rifampin, and 400 (21.6%) were susceptible to all first-line agents. Ciprofloxacin resistance was found in 33 (1.8%) of the referral-sample isolates. Most ciprofloxacin-resistant isolates (25 [75.8%]) were resistant to isoniazid and rifampin. CONCLUSIONS Despite widespread use of fluoroquinolones for treatment of common bacterial infections, resistance among clinical isolates of M. tuberculosis in the United States and Canada remains rare, occurring primarily among multidrug-resistant strains.
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Affiliation(s)
- Lorna Bozeman
- Division of Tuberculosis Elimination, Centers for Disease Control and Prevention, Atlanta, GA, USA
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20
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Sanders CA, Nieda RR, Desmond EP. Validation of the use of Middlebrook 7H10 agar, BACTEC MGIT 960, and BACTEC 460 12B media for testing the susceptibility of Mycobacterium tuberculosis to levofloxacin. J Clin Microbiol 2005; 42:5225-8. [PMID: 15528718 PMCID: PMC525139 DOI: 10.1128/jcm.42.11.5225-5228.2004] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Levofloxacin, the active l-isomer of the quinolone ofloxacin, is now widely accepted for treatment of multidrug-resistant tuberculosis. Because the drug is now widely used, we sought to establish susceptibility test conditions for Mycobacterium tuberculosis against levofloxacin by the traditional reference method, agar proportion (AP), the commonly used BACTEC 460 radiometric system, and the newer BACTEC MGIT 960 method. To determine the stability of levofloxacin in the two newer test systems (BACTEC 460 and BACTEC MGIT 960), media containing subinhibitory levels of levofloxacin were prepared and stored at 4 and 37 degrees C for 14 days. The stored media were inoculated with H37Rv, and the drug activity was compared to freshly prepared media. Results show that levofloxacin is stable over the course of testing. Next, optimum levofloxacin test concentrations were determined for AP, BACTEC 460, and BACTEC MGIT 960 methods. MICs were determined for 32 pan-susceptible isolates of M. tuberculosis obtained from presumably untreated patients and 14 quinolone-resistant isolates. The levofloxacin-resistant strains either were isolated from patients who remained culture-positive despite treatment with a quinolone agent (six strains) or contained known mutations in gyrA (eight strains). Levofloxacin MICs resulted in a bimodal pattern with values for resistant strains consistently higher than those for pan-susceptible strains. Results show that levofloxacin concentrations of 2 microg/ml (BACTEC 460 and BACTEC MGIT 960) and 1 microg/ml (AP) inhibited the growth of all pan-susceptible strains while permitting the growth of all levofloxacin-resistant strains. Confirmatory tests with a subset of pan-susceptible and levofloxacin-resistant isolates validated the selected test concentrations.
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21
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Cheng AFB, Yew WW, Chan EWC, Chin ML, Hui MMM, Chan RCY. Multiplex PCR amplimer conformation analysis for rapid detection of gyrA mutations in fluoroquinolone-resistant Mycobacterium tuberculosis clinical isolates. Antimicrob Agents Chemother 2004; 48:596-601. [PMID: 14742214 PMCID: PMC321542 DOI: 10.1128/aac.48.2.596-601.2004] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A new strategy known as multiplex PCR amplimer conformation was developed for detection of mutation in the gyrA gene of 138 clinical isolates of Mycobacterium tuberculosis. The method generated a single-stranded and heteroduplex DNA banding pattern of multiplex PCR amplimers of the region of interest that was extremely sensitive to specific mutations, thus enabling much more sensitive and reliable mutation analysis compared to the standard single-stranded conformation polymorphism technique. The genetic profiles of the gyrA gene of the 138 isolates as detected by MPAC were confirmed by nucleotide sequencing and were found to correlate strongly with the in vitro susceptibilities of the mutant strains to six fluoroquinolones (ofloxacin, levofloxacin, sparfloxacin, moxifloxacin, gatifloxacin, and sitafloxacin). All 32 isolates that contained gyrA mutations exhibited cross-resistance to the six fluoroquinolones (ofloxacin MIC for 90% of strains > 16 mg/liter), although moxifloxacin, gatifloxacin, and sitafloxacin (MIC for 90% of strains </= 4 mg/liter) were apparently more active than ofloxacin, levofloxacin, and sparfloxacin (MIC for 90% of strains >/==" BORDER="0"> 16 mg/liter). All gyrA mutations were clustered in codons 90, 91, and 94, and aspartic acid 94 was most frequently mutated. Twenty-three isolates without gyrA mutations were also found to exhibit reduced susceptibility to ofloxacin (MIC for 90% of strains = 4 mg/liter), but largely remained susceptible to other drugs (MIC for 90% of strains </= 1 mg/liter). Another 83 isolates without mutations were fully susceptible to all six fluoroquinolones (ofloxacin MIC for 90% of strains = 1 mg/liter). In conclusion, high-level phenotypic resistance to fluoroquinolones among M. tuberculosis clinical isolates, which appears to be predominantly due to gyrA mutations, may be readily detected by genotyping techniques such as multiplex PCR amplimer conformation.
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Affiliation(s)
- Augustine F B Cheng
- Department of Microbiology, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong, China.
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22
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Perlman DC, Segal Y, Rosenkranz S, Rainey PM, Peloquin CA, Remmel RP, Chirgwin K, Salomon N, Hafner R. The Clinical Pharmacokinetics of Pyrazinamide in HIV‐Infected Persons with Tuberculosis. Clin Infect Dis 2004; 38:556-64. [PMID: 14765350 DOI: 10.1086/381096] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2003] [Accepted: 09/23/2003] [Indexed: 11/04/2022] Open
Abstract
The pharmacokinetics of pyrazinamide (PZA) in patients with human immunodeficiency virus (HIV)-related tuberculosis are incompletely characterized. Serum PZA concentrations were determined at 2, 6, and 10 h after dosing in 48 subjects with HIV-related tuberculosis. Estimates of drug exposure using 2-h concentrations and 2- and 3-time point estimates of area under time-concentration curves (AUCs) were compared. For daily dosing, 2-h concentrations less than low and very low literature-defined cut points (i.e., 20 and 10 mg/L) were noted for 2 subjects (4%) and 1 subject (2%), respectively. For intermittent PZA dosing, 1 subject (4%) had a 2-h concentration that was less than the low cut point (25 mg/L). Correlations between 2-h concentration and AUC estimates based on 2- or 3-time point concentration determinations were strong. In HIV-infected persons receiving antituberculosis regimens containing PZA, lower-than-expected 2-h concentrations are uncommon. For therapeutic monitoring of PZA drug exposure, determination of a 2-h postdose concentration appears as reliable as 2- or 3-time point estimates of the AUC for PZA.
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Rawat R, Whitty A, Tonge PJ. The isoniazid-NAD adduct is a slow, tight-binding inhibitor of InhA, the Mycobacterium tuberculosis enoyl reductase: adduct affinity and drug resistance. Proc Natl Acad Sci U S A 2003; 100:13881-6. [PMID: 14623976 PMCID: PMC283515 DOI: 10.1073/pnas.2235848100] [Citation(s) in RCA: 230] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Isoniazid (INH), a frontline antitubercular drug, inhibits InhA, the enoyl reductase from Mycobacterium tuberculosis, by forming a covalent adduct with the NAD cofactor. Here, we report that the INH-NAD adduct is a slow, tight-binding competitive inhibitor of InhA. Demonstration that the adduct binds to WT InhA by a two-step enzyme inhibition mechanism, with initial, weak binding (K(-1) = 16 +/- 11 nM) followed by slow conversion to a final inhibited complex (EI*) with overall Ki = 0.75 +/- 0.08 nM, reconciles existing contradictory values for the inhibitory potency of INH-NAD for InhA. The first order rate constant for conversion of the initial EI complex to EI* (k2 = 0.13 +/- 0.01 min(-1)) is similar to the maximum rate constant observed for InhA inhibition in reaction mixtures containing InhA, INH, NADH, and the INH-activating enzyme KatG (catalase/peroxidase from M. tuberculosis), consistent with an inhibition mechanism in which the adduct forms in solution rather than on the enzyme. Importantly, three mutations that correlate with INH resistance, I21V, I47T, and S94A, have little impact on the inhibition constants. Thus, drug resistance does not result simply from a reduction in affinity of INH-NAD for pure InhA. Instead, we hypothesize that protein-protein interactions within the FASII complex are critical to the mechanism of INH action. Finally, for M161V, an InhA mutation that correlates with resistance to the common biocide triclosan in Mycobacterium smegmatis, binding to form the initial EI complex is significantly weakened, explaining why this mutant inactivates more slowly than WT InhA when incubated with INH, NADH, and KatG.
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Affiliation(s)
- Richa Rawat
- Department of Chemistry, Stony Brook University, Stony Brook, NY 11794-3400, USA
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Ginsburg AS, Woolwine SC, Hooper N, Benjamin WH, Bishai WR, Dorman SE, Sterling TR. The rapid development of fluoroquinolone resistance in M. tuberculosis. N Engl J Med 2003; 349:1977-8. [PMID: 14614180 DOI: 10.1056/nejm200311133492023] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Ginsburg AS, Hooper N, Parrish N, Dooley KE, Dorman SE, Booth J, Diener-West M, Merz WG, Bishai WR, Sterling TR. Fluoroquinolone resistance in patients with newly diagnosed tuberculosis. Clin Infect Dis 2003; 37:1448-52. [PMID: 14614666 DOI: 10.1086/379328] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2003] [Accepted: 07/20/2003] [Indexed: 11/03/2022] Open
Abstract
Fluoroquinolones are widely used for the treatment of bacterial infections and are also second-line therapy for tuberculosis. However, fluoroquinolone resistance in patients with newly diagnosed cases of tuberculosis is not routinely assessed. We performed in vitro susceptibility testing of Mycobacterium tuberculosis to fluoroquinolones for all culture-confirmed tuberculosis cases in adults that were diagnosed at Johns Hopkins Hospital (Baltimore) between January 1998 and March 2002. Fifty-five patients were included in the study; 19 received fluoroquinolone monotherapy before the initiation of antituberculosis therapy. Two of 55 M. tuberculosis isolates (4%; 95% CI, 1%-13%) had decreased susceptibility to fluoroquinolones, including 2 of 19 of those from patients who had received fluoroquinolones (11%; 95% CI, 1%-33%) and 0 of 36 isolates from those who had not (95% CI, 0%-10%). The 2 fluoroquinolone-resistant M. tuberculosis strains were both from patients with acquired immunodeficiency syndrome and a CD4+ lymphocyte count of <50 cells/mm3. The incidence of M. tuberculosis fluoroquinolone resistance in this small sample of patients with newly diagnosed tuberculosis was high, particularly among patients with prior fluoroquinolone exposure.
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Affiliation(s)
- Amy Sarah Ginsburg
- Center for Tuberculosis Research, Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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Abstract
The history of chemotherapy of tuberculosis commenced in 1944 with the discovery of streptomycin. Currently, short-course chemotherapy comprising rifampicin, isoniazid, pyrazinamide and ethambutol/streptomycin administered under directly observed settings for 6 months (initially all four drugs followed by the former two drugs), constitutes the cornerstone treatment for pulmonary tuberculosis. Multi-drug resistant tuberculosis requires alternative chemotherapy, ideally in the form of individualised regimens, for management. To improve on the duration of chemotherapy for drug-susceptible tuberculosis and to achieve better treatment for multi-drug resistant tuberculosis as well as latent tuberculosis infection, there arises a genuine need for new drugs. The quest for new agents is, however, impeded by obstacles. Hopefully, tackling these through collaborative public-private partnerships on an international scale will lead to a fruitful outcome.
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Affiliation(s)
- Peter D O Davies
- Tuberculosis Research Unit, Cardiothoracic Centre, Liverpool, L14 3PE, UK.
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27
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Ginsburg AS, Grosset JH, Bishai WR. Fluoroquinolones, tuberculosis, and resistance. THE LANCET. INFECTIOUS DISEASES 2003; 3:432-42. [PMID: 12837348 DOI: 10.1016/s1473-3099(03)00671-6] [Citation(s) in RCA: 296] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Although the fluoroquinolones are presently used to treat tuberculosis primarily in cases involving resistance or intolerance to first-line antituberculosis therapy, these drugs are potential first-line agents and are under study for this indication. However, there is concern about the development of fluoroquinolone resistance in Mycobacterium tuberculosis, particularly when administered as monotherapy or as the only active agent in a failing multidrug regimen. Treatment failures as well as relapses have been documented under such conditions. With increasing numbers of fluoroquinolone prescriptions and the expanded use of these broad-spectrum agents for many infections, the selective pressure of fluoroquinolone use results in the ready emergence of fluoroquinolone resistance in a diversity of organisms, including M tuberculosis. Among M tuberculosis, resistance is emerging and may herald a significant future threat to the long-term clinical utility of fluoroquinolones. Discussion and education regarding appropriate use are necessary to preserve the effectiveness of this antibiotic class against the hazard of growing resistance.
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Affiliation(s)
- Amy Sarah Ginsburg
- Center for Tuberculosis Research, Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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28
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Parikh SL, Xiao G, Tonge PJ. Inhibition of InhA, the enoyl reductase from Mycobacterium tuberculosis, by triclosan and isoniazid. Biochemistry 2000; 39:7645-50. [PMID: 10869170 DOI: 10.1021/bi0008940] [Citation(s) in RCA: 176] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Structural and genetic studies indicate that the antibacterial compound triclosan, an additive in many personal care products, is an inhibitor of EnvM, the enoyl reductase from Escherichia coli. Here we show that triclosan specifically inhibits InhA, the enoyl reductase from Mycobacterium tuberculosis and a target for the antitubercular drug isoniazid. Binding of triclosan to wild-type InhA is uncompetitive with respect to both NADH and trans-2-dodecenoyl-CoA, with K(i)' values of 0.22+/-0.02 and 0.21+/-0.01 microM, respectively. Replacement of Y158, the catalytic tyrosine residue, with Phe, reduces the affinity of triclosan for the enzyme and results in noncompetitive inhibition, with K(i) and K(i)' values of 36+/-5 and 47+/-5 microM, respectively. Consequently, the Y158 hydroxyl group is important for triclosan binding, suggesting that triclosan binds in similar ways to both InhA and EnvM. In addition, the M161V and A124V InhA mutants, which result in resistance of Mycobacterium smegmatis to triclosan, show significantly reduced affinity for triclosan. Inhibition of M161V is noncompetitive with K(i)' = 4.3+/-0.5 microM and K(i) = 4.4+/-0.9 microM, while inhibition of A124V is uncompetitive with K(i)' = 0. 81 +/- 0.11 microM. These data support the hypothesis that the mycobacterial enoyl reductases are targets for triclosan. The M161V and A124V enzymes are also much less sensitive to isoniazid compared to the wild-type enzyme, indicating that triclosan can stimulate the emergence of isoniazid-resistant enoyl reductases. In contrast, I47T and I21V, two InhA mutations that occur in isoniazid-resistant clinical isolates of M. tuberculosis, show unimpaired inhibition by triclosan, with uncompetitive inhibition constants (K(i)') of 0.18+/-0.01 and 0.12+/- 0.01 microM, respectively. The latter result indicates that InhA inhibitors targeted at the enoyl substrate binding site may be effective against existing isoniazid-resistant strains of M. tuberculosis.
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Affiliation(s)
- S L Parikh
- Department of Chemistry and Graduate Programs in Biophysics and Molecular and Cellular Biochemistry, State University of New York at Stony Brook, New York 11794-3400, USA
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Yew WW, Chan CK, Chau CH, Tam CM, Leung CC, Wong PC, Lee J. Outcomes of patients with multidrug-resistant pulmonary tuberculosis treated with ofloxacin/levofloxacin-containing regimens. Chest 2000; 117:744-51. [PMID: 10713001 DOI: 10.1378/chest.117.3.744] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
OBJECTIVE To analyze outcomes of patients with multidrug-resistant tuberculosis (MDR-TB) treated with ofloxacin/levofloxacin-containing regimens. MATERIALS AND METHODS From February 1990 through June 1997, 63 MDR-TB patients (with bacillary resistance to at least isoniazid and rifampin in vitro) were analyzed retrospectively. Twenty-two patients (34.9%) had had no previous antituberculosis chemotherapy. Each patient received either ofloxacin (53) or levofloxacin (10) even though 13 patients had bacilli resistant to ofloxacin in vitro. The other accompanying drugs mainly included aminoglycosides, cycloserine, ethionamide/prothionamide, and pyrazinamide. Sputum smear and culture examinations for acid-fast bacilli (AFB) were performed monthly for the initial 6 months and then at 2- to 3-month intervals until the end of treatment. Comparison was made between clinical successes and failures using univariate and multiple logistic regression analyses for the following variables: age, sex, presence of cavitation, extent of disease, sputum smear positivity, in vitro resistance to ofloxacin, in vitro resistance to streptomycin and/or ethambutol, treatment adherence, and the number of drugs per regimen. RESULTS Fifty-one patients (81.0%) were cured, nine patients (14.3%) failed, and three patients (4.7%) died. For the entire group, the mean duration of treatment was 14.0 months, and the mean number of drugs was 4.7. Mean durations of chemotherapy in successful and failed patients were 14.5 and 14.2 months, respectively. Mean time for sputum smear and culture conversions were 1.7 and 2.1 months, respectively. Only cavitation, resistance to ofloxacin, and poor adherence were found to be variables independently associated with adverse outcomes (p < 0.05; odds ratios = 15.9, 13.5, 12.8, respectively). Negative sputum cultures after 2 and 3 months of therapy were 100% predictive of cure. Positive sputum cultures after 2 and 3 months were 52.3% and 84.6% predictive of failure, respectively. One patient (2.1%) relapsed after apparent cure. Twenty-five patients experienced adverse drug reactions, but only 12 of them needed drug modifications. CONCLUSION Most MDR-TB patients can be treated effectively with ofloxacin/levofloxacin-containing regimens. Presence of cavitation, resistance to ofloxacin in vitro, and poor adherence to therapy portend treatment failure. Monitoring monthly sputum culture for AFB in the initial months of chemotherapy helps predict clinical outcomes.
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Affiliation(s)
- W W Yew
- Tuberculosis and Chest Unit, Grantham Hospital, Hong Kong, China
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Parikh S, Moynihan DP, Xiao G, Tonge PJ. Roles of tyrosine 158 and lysine 165 in the catalytic mechanism of InhA, the enoyl-ACP reductase from Mycobacterium tuberculosis. Biochemistry 1999; 38:13623-34. [PMID: 10521269 DOI: 10.1021/bi990529c] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The role of tyrosine 158 (Y158) and lysine 165 (K165) in the catalytic mechanism of InhA, the enoyl-ACP reductase from Mycobacterium tuberculosis, has been investigated. These residues have been identified as putative catalytic residues on the basis of structural and sequence homology with the short chain alcohol dehydrogenase family of enzymes. Replacement of Y158 with phenylalanine (Y158F) and with alanine (Y158A) results in 24- and 1500-fold decreases in k(cat), respectively, while leaving K(m) for the substrate, trans-2-dodecenoyl-CoA, unaffected. Remarkably, however, replacement of Y158 with serine (Y158S) results in an enzyme with wild-type activity. Kinetic isotope effect studies indicate that the transfer of a solvent-exchangeable proton is partially rate-limiting for the wild-type and Y158S enzymes, but not for the Y158A enzyme. These data indicate that Y158 does not function formally as a proton donor in the reaction but likely functions as an electrophilic catalyst, stabilizing the transition state for hydride transfer by hydrogen bonding to the substrate carbonyl. A conformational change involving rotation of the Y158 side chain upon binding of the enoyl substrate to the enzyme is proposed as an explanation for the inverse solvent isotope effect observed on V/K(DD-CoA) when either NADH or NADD is used as the reductant. These data are consistent with the recently published structure of a C16 fatty acid substrate bound to InhA that shows Y158 hydrogen bonded to the substrate carbonyl group and rotated from the position it occupies in the InhA-NADH binary complex [Rozwarski, D. A., Vilcheze, C., Sugantino, M., Bittman, R., and Sacchettini, J. C. (1999) J. Biol. Chem. 274, 15582-15589]. Finally, the role of K165 has been analyzed using site-directed mutagenesis. Replacement of K165 with glutamine (K165Q) and arginine (K165R) has no effect on the enzyme's catalytic ability or on its ability to bind NADH. However, the K165A and K165M enzymes are unable to bind NADH, indicating that K165 has a primary role in cofactor binding.
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Affiliation(s)
- S Parikh
- Department of Chemistry, State University of New York at Stony Brook 11794-3400, USA
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Oleksijew A, Meulbroek J, Ewing P, Jarvis K, Mitten M, Paige L, Tovcimak A, Nukkula M, Chu D, Alder JD. In vivo efficacy of ABT-255 against drug-sensitive and -resistant Mycobacterium tuberculosis strains. Antimicrob Agents Chemother 1998; 42:2674-7. [PMID: 9756775 PMCID: PMC105917 DOI: 10.1128/aac.42.10.2674] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Current therapy for pulmonary tuberculosis involves 6 months of treatment with isoniazid, pyrazinamide, rifampin, and ethambutol or streptomycin for reliable treatment efficacy. The long treatment period increases the probability of noncompliance, leading to the generation of multidrug-resistant isolates of Mycobacterium tuberculosis. A treatment option that significantly shortened the course of therapy, or a new class of antibacterial effective against drug-resistant M. tuberculosis would be of value. ABT-255 is a novel 2-pyridone antibacterial agent which demonstrates in vitro potency and in vivo efficacy against drug-susceptible and drug-resistant M. tuberculosis strains. By the Alamar blue reduction technique, the MIC of ABT-255 against susceptible strains of M. tuberculosis ranged from 0.016 to 0.031 microg/ml. The MIC of ABT-255 against rifampin- or ethambutol-resistant M. tuberculosis isolates was 0.031 microg/ml. In a murine model of pulmonary tuberculosis, 4 weeks of oral ABT-255 therapy produced a 2- to 5-log10 reduction in viable drug-susceptible M. tuberculosis counts from lung tissue. Against drug-resistant strains of M. tuberculosis, ABT-255 produced a 2- to 3-log10 reduction in viable bacterial counts from lung tissue. ABT-255 is a promising new antibacterial agent with activity against M. tuberculosis.
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Affiliation(s)
- A Oleksijew
- Experimental Therapeutics and Pharmacology, Abbott Laboratories, Abbott Park, Illinois 60064, USA.
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