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Anthwal D, Lavania S, Gupta RK, Verma A, Myneedu VP, Sharma PP, Verma H, Malhotra V, Gupta A, Gupta NK, Sarin R, Haldar S, Tyagi JS. Development and evaluation of novel bio-safe filter paper-based kits for sputum microscopy and transport to directly detect Mycobacterium tuberculosis and associated drug resistance. PLoS One 2019; 14:e0220967. [PMID: 31408508 PMCID: PMC6692035 DOI: 10.1371/journal.pone.0220967] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 07/26/2019] [Indexed: 11/18/2022] Open
Abstract
India has the highest burden of Tuberculosis (TB) and multidrug-resistant TB (MDR-TB) worldwide. Innovative technology is the need of the hour to identify these cases that remain either undiagnosed or inadequately diagnosed due to the unavailability of appropriate tools at primary healthcare settings. We developed and evaluated 3 kits, namely ‘TB Detect’ (containing BioFM-Filter device), ‘TB Concentration and Transport’ (containing Trans-Filter device) and ‘TB DNA Extraction’ kits. These kits enable bio-safe equipment-free concentration of sputum on filters and improved fluorescence microscopy at primary healthcare centres, ambient temperature transport of dried inactivated sputum filters to central laboratories and molecular detection of drug resistance by PCR and DNA sequencing (Mol-DST). In a 2-site evaluation (n = 1190 sputum specimens) on presumptive TB patients, BioFM-Filter smear exhibited a significant increase in positivity of 7% and 4% over ZN smear and LED-FM smear (p<0.05), respectively and an increment in smear grade status (1+ or 2+ to 3+) of 16% over ZN smear and 20% over LED-FM smear. The sensitivity of Mol-DST in presumptive MDR-TB and XDR-TB cases (n = 148) was 90% for Rifampicin (95% confidence interval [CI], 78–96%), 84% for Isoniazid (95% CI, 72–92%), 83% for Fluoroquinolones (95% CI, 66–93%) and 75% for Aminoglycosides (95% CI, 35–97%), using phenotypic DST as the reference standard. Test specificity was 88–93% and concordance was ~89–92% (κ value 0.8–0.9). The patient-friendly kits described here address several of the existing challenges and are designed to provide ‘Universal Access’ to rapid TB diagnosis, including drug-resistant disease. Their utility was demonstrated by application to sputum at 2 sites in India. Our findings pave the way for larger studies in different point-of-care settings, including high-density urban areas and remote geographical locations.
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Affiliation(s)
- Divya Anthwal
- Center for Bio-design and Diagnostics, Translational Health Science and Technology Institute, NCR Biotech Science Cluster, 3rd Milestone, Faridabad–Gurgaon Expressway, Faridabad, India
| | - Surabhi Lavania
- Department of Biotechnology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
| | - Rakesh Kumar Gupta
- Center for Bio-design and Diagnostics, Translational Health Science and Technology Institute, NCR Biotech Science Cluster, 3rd Milestone, Faridabad–Gurgaon Expressway, Faridabad, India
| | - Ajoy Verma
- Department of Microbiology, National Institute of Tuberculosis and Respiratory Diseases, Mehrauli, New Delhi, India
| | - Vithal Prasad Myneedu
- Department of Microbiology, National Institute of Tuberculosis and Respiratory Diseases, Mehrauli, New Delhi, India
| | - Prem Prakash Sharma
- Department of Microbiology, National Institute of Tuberculosis and Respiratory Diseases, Mehrauli, New Delhi, India
| | | | | | - Ashawant Gupta
- Advanced Microdevices Pvt Ltd, Industrial Area, Ambala Cantt, India
| | | | - Rohit Sarin
- Department of Microbiology, National Institute of Tuberculosis and Respiratory Diseases, Mehrauli, New Delhi, India
- * E-mail: (JST); (SH); (RS)
| | - Sagarika Haldar
- Center for Bio-design and Diagnostics, Translational Health Science and Technology Institute, NCR Biotech Science Cluster, 3rd Milestone, Faridabad–Gurgaon Expressway, Faridabad, India
- * E-mail: (JST); (SH); (RS)
| | - Jaya Sivaswami Tyagi
- Center for Bio-design and Diagnostics, Translational Health Science and Technology Institute, NCR Biotech Science Cluster, 3rd Milestone, Faridabad–Gurgaon Expressway, Faridabad, India
- Department of Biotechnology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
- * E-mail: (JST); (SH); (RS)
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Genetics and roadblocks of drug resistant tuberculosis. INFECTION GENETICS AND EVOLUTION 2018; 72:113-130. [PMID: 30261266 DOI: 10.1016/j.meegid.2018.09.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 09/20/2018] [Accepted: 09/22/2018] [Indexed: 11/22/2022]
Abstract
Considering the extensive evolutionary history of Mycobacterium tuberculosis, anti-Tuberculosis (TB) drug therapy exerts a recent selective pressure. However, in a microorganism devoid of horizontal gene transfer and with a strictly clonal populational structure such as M. tuberculosis the usual, but not sole, path to overcome drug susceptibility is through de novo mutations on a relatively strict set of genes. The possible allelic diversity that can be associated with drug resistance through several mechanisms such as target alteration or target overexpression, will dictate how these genes can become associated with drug resistance. The success demonstrated by this pathogenic microbe in this latter process and its ability to spread is currently one of the major obstacles to an effective TB elimination. This article reviews the action mechanism of the more important anti-TB drugs, including bedaquiline and delamanid, along with new findings on specific resistance mechanisms. With the development, validation and endorsement of new in vitro molecular tests for drug resistance, knowledge on these resistance mechanisms and microevolutionary dynamics leading to the emergence and fixation of drug resistance mutations within the host is highly important. Additionally, the fitness toll imposed by resistance development is also herein discussed together with known compensatory mechanisms. By elucidating the possible mechanisms that enable one strain to reacquire the original fitness levels, it will be theoretically possible to make more informed decisions and develop novel strategies that can force M. tuberculosis microevolutionary trajectory down through a path of decreasing fitness levels.
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Bentaleb EM, El Messaoudi MD, Abid M, Messaoudi M, Yetisen AK, Sefrioui H, Amzazi S, Ait Benhassou H. Plasmid-based high-resolution melting analysis for accurate detection of rpoB mutations in Mycobacterium tuberculosis isolates from Moroccan patients. BMC Infect Dis 2017; 17:548. [PMID: 28784099 PMCID: PMC5547500 DOI: 10.1186/s12879-017-2666-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 08/02/2017] [Indexed: 11/16/2022] Open
Abstract
Background Rapid diagnosis of drug resistance in tuberculosis (TB) is pivotal for the timely initiation of effective antibiotic treatment to prevent the spread of drug-resistant strains. The development of low-cost, rapid and robust methods for drug-resistant TB detection is highly desirable for resource-limited settings. Methods We report the use of an in house plasmid-based quantitative polymerase chain reaction-high-resolution melting (qPCR-HRM) analysis for the detection of mutations related to rifampicin-resistant Mycobacterium tuberculosis (MTB) in clinical isolates from Moroccan patients. Five recombinant plasmids containing predominant mutations (S531L, S531W, H526Y and D516V) and the wild-type sequence of the Rifampicin Resistance-Determining Region (RRDR) have been used as controls to screen 45 rifampicin-resistant and 22 rifampicin-susceptible MTB isolates. Results The sensitivity and the specificity of the qPCR-HRM analysis were 88.8% and 100% respectively as compared to rifampicin Drug Susceptibility Testing (DST). The results of qPCR-HRM and DNA sequencing had a concordance of 100%. Conclusion Our qPCR-HRM assay is a sensitive, accurate and cost-effective assay for the high-throughput screening of mutation-based drug resistance in TB reference laboratories.
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Affiliation(s)
- El Mehdi Bentaleb
- Medical Biotechnology Center, Moroccan Foundation for Advanced Science, Innovation and Research (MAScIR), Rabat Design Center, Avenue Mohamed El Jazouli - Madinat Al Irfane, 10100, Rabat, Morocco.,Laboratory of Biochemistry and Immunology, Faculty of Sciences, Mohammed V University, Rabat, Morocco
| | | | - Mohammed Abid
- Laboratory of Mycobacteria Genetics, Pasteur Institute of Morocco, Tangier, Morocco
| | - Malika Messaoudi
- Laboratory of Tuberculosis, Pasteur Institute of Morocco, Casablanca, Morocco
| | - Ali K Yetisen
- Harvard-MIT Division of Health Sciences and Technology, Harvard University and Massachusetts Institute of Technology, 65 Landsdowne Street, Cambridge, MA, 02139, USA
| | - Hassan Sefrioui
- Medical Biotechnology Center, Moroccan Foundation for Advanced Science, Innovation and Research (MAScIR), Rabat Design Center, Avenue Mohamed El Jazouli - Madinat Al Irfane, 10100, Rabat, Morocco
| | - Saaïd Amzazi
- Laboratory of Biochemistry and Immunology, Faculty of Sciences, Mohammed V University, Rabat, Morocco
| | - Hassan Ait Benhassou
- Medical Biotechnology Center, Moroccan Foundation for Advanced Science, Innovation and Research (MAScIR), Rabat Design Center, Avenue Mohamed El Jazouli - Madinat Al Irfane, 10100, Rabat, Morocco.
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Drobniewski F, Cooke M, Jordan J, Casali N, Mugwagwa T, Broda A, Townsend C, Sivaramakrishnan A, Green N, Jit M, Lipman M, Lord J, White PJ, Abubakar I. Systematic review, meta-analysis and economic modelling of molecular diagnostic tests for antibiotic resistance in tuberculosis. Health Technol Assess 2016; 19:1-188, vii-viii. [PMID: 25952553 DOI: 10.3310/hta19340] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Drug-resistant tuberculosis (TB), especially multidrug-resistant (MDR, resistance to rifampicin and isoniazid) disease, is associated with a worse patient outcome. Drug resistance diagnosed using microbiological culture takes days to weeks, as TB bacteria grow slowly. Rapid molecular tests for drug resistance detection (1 day) are commercially available and may promote faster initiation of appropriate treatment. OBJECTIVES To (1) conduct a systematic review of evidence regarding diagnostic accuracy of molecular genetic tests for drug resistance, (2) conduct a health-economic evaluation of screening and diagnostic strategies, including comparison of alternative models of service provision and assessment of the value of targeting rapid testing at high-risk subgroups, and (3) construct a transmission-dynamic mathematical model that translates the estimates of diagnostic accuracy into estimates of clinical impact. REVIEW METHODS AND DATA SOURCES A standardised search strategy identified relevant studies from EMBASE, PubMed, MEDLINE, Bioscience Information Service (BIOSIS), System for Information on Grey Literature in Europe Social Policy & Practice (SIGLE) and Web of Science, published between 1 January 2000 and 15 August 2013. Additional 'grey' sources were included. Quality was assessed using quality assessment of diagnostic accuracy studies version 2 (QUADAS-2). For each diagnostic strategy and population subgroup, a care pathway was constructed to specify which medical treatments and health services that individuals would receive from presentation to the point where they either did or did not complete TB treatment successfully. A total cost was estimated from a health service perspective for each care pathway, and the health impact was estimated in terms of the mean discounted quality-adjusted life-years (QALYs) lost as a result of disease and treatment. Costs and QALYs were both discounted at 3.5% per year. An integrated transmission-dynamic and economic model was used to evaluate the cost-effectiveness of introducing rapid molecular testing (in addition to culture and drug sensitivity testing). Probabilistic sensitivity analysis was performed to evaluate the impact on cost-effectiveness of diagnostic and treatment time delays, diagnosis and treatment costs, and associated QALYs. RESULTS A total of 8922 titles and abstracts were identified, with 557 papers being potentially eligible. Of these, 56 studies contained sufficient test information for analysis. All three commercial tests performed well when detecting drug resistance in clinical samples, although with evidence of heterogeneity between studies. Pooled sensitivity for GenoType® MTBDRplus (Hain Lifescience, Nehren, Germany) (isoniazid and rifampicin resistance), INNO-LiPA Rif.TB® (Fujirebio Europe, Ghent, Belgium) (rifampicin resistance) and Xpert® MTB/RIF (Cepheid Inc., Sunnyvale, CA, USA) (rifampicin resistance) was 83.4%, 94.6%, 95.4% and 96.8%, respectively; equivalent pooled specificity was 99.6%, 98.2%, 99.7% and 98.4%, respectively. Results of the transmission model suggest that all of the rapid assays considered here, if added to the current diagnostic pathway, would be cost-saving and achieve a reduction in expected QALY loss compared with current practice. GenoType MTBDRplus appeared to be the most cost-effective of the rapid tests in the South Asian population, although results were similar for GeneXpert. In all other scenarios GeneXpert appeared to be the most cost-effective strategy. CONCLUSIONS Rapid molecular tests for rifampicin and isoniazid resistance were sensitive and specific. They may also be cost-effective when added to culture drug susceptibility testing in the UK. There is global interest in point-of-care testing and further work is needed to review the performance of emerging tests and the wider health-economic impact of decentralised testing in clinics and primary care, as well as non-health-care settings, such as shelters and prisons. STUDY REGISTRATION This study is registered as PROSPERO CRD42011001537. FUNDING The National Institute for Health Research Health Technology Assessment programme.
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Affiliation(s)
- Francis Drobniewski
- Public Health England National Mycobacterium Reference Laboratory, London, UK
| | - Mary Cooke
- Centre for Infectious Disease Epidemiology, Research Department of Infection and Population Health, University College London, London, UK
| | - Jake Jordan
- Health Economics Research Group, Brunel University, Uxbridge, UK
| | - Nicola Casali
- Department of Infectious Diseases and Immunity, Imperial College London, London, UK
| | - Tendai Mugwagwa
- Modelling and Economics Unit, Centre for Infectious Disease Surveillance and Control, Public Health England, London, UK
| | - Agnieszka Broda
- Department of Infectious Diseases and Immunity, Imperial College London, London, UK
| | | | | | - Nathan Green
- Modelling and Economics Unit, Centre for Infectious Disease Surveillance and Control, Public Health England, London, UK
| | - Mark Jit
- Modelling and Economics Unit, Centre for Infectious Disease Surveillance and Control, Public Health England, London, UK
| | - Marc Lipman
- Division of Medicine, University College London, London, UK
| | - Joanne Lord
- Health Economics Research Group, Brunel University, Uxbridge, UK
| | - Peter J White
- Modelling and Economics Unit, Centre for Infectious Disease Surveillance and Control, Public Health England, London, UK
| | - Ibrahim Abubakar
- Centre for Infectious Disease Epidemiology, Research Department of Infection and Population Health, University College London, London, UK
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Sequence analysis for detection of drug resistance in Mycobacterium tuberculosis complex isolates from the Central Region of Cameroon. BMC Microbiol 2014; 14:113. [PMID: 24884632 PMCID: PMC4017682 DOI: 10.1186/1471-2180-14-113] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Accepted: 04/29/2014] [Indexed: 11/22/2022] Open
Abstract
Background The potential of genetic testing to rapidly diagnose drug resistance has lead to the development of new diagnostic assays. However, prior to implementation in a given setting, the association of specific mutations with specific drug resistance phenotypes should be evaluated. The purpose of this study was to evaluate molecular markers in predicting drug resistance in the Central Region of Cameroon. Results From April 2010 and March 2011, 725 smear positive pulmonary tuberculosis patients were enrolled and all positive cultures were tested for drug susceptibility. A total of 63 drug resistant and 100 drug sensitive Mycobacterium tuberculosis complex clinical isolates were screened for genetic mutations in katG, inhA, ahpC, rpoB, rpsL, rrs, gidB and embCAB loci using DNA sequencing. Of the 44 isoniazid resistant (INHR) isolates (24 high level, 1 μg/ml and 20 low level, 0.2 μg/ml), 73% (32/44) carried the katG315 and/or the -15 inhA promoter mutations. Of the 24 high level INHR, 17 (70.8%) harbored katG315 mutation, 1 a point mutation (-15C → T) in the inhA promoter and 6 were (25.0%) wild types. Thus, for INHR high level detection, katG315 mutation had a specificity and a sensitivity of 100% and 70.8% respectively. Of the 20 low level INHR, 10 (50.0%) had a -15C → T mutation in the inhA promoter region, and 1 (2.2%) a -32G → A mutation in the ahpC promoter region. All of the 7 rifampicin resistant (RIFR) isolates carried mutations in the rpoB gene (at codons Ser531Leu (71.4%), His526Asp (14.3%), and Asp516Val (14.3%)). Of the 27 streptomycin resistant (SMR) isolates, 7 carried mutations at the rpsL and the gidB genes. 1 of the 2 ethambutol resistant (EMBR) isolates displayed a mutation in embB gene. Conclusion This study provided the first molecular investigation assessing the correlation of phenotypic to genotypic characteristics on MTB isolates from the Central Region of Cameroon using DNA sequencing. Mutations on rpoB, katG315 and -15 point mutations in inhA promoter loci could be used as markers for RIF and INH -resistance detection respectively.
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Park JY, Kwon KT. Clinical Usefulness of rpoBGene Sequence Analysis in Lymph Node Tuberculosis. Infect Chemother 2012. [DOI: 10.3947/ic.2012.44.5.357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Ji-Young Park
- Department of Pathology, Kyungpook National University, School of Medicine, Daegu, Korea
| | - Ki Tae Kwon
- Division of Infectious Diseases, Daegu Fatima Hospital, Daegu, Korea
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Lee J, Yun YJ, Kqueen CY, Lee JH, Kim HY, Kim YR, Kook YH, Lee KH. pncAMutations in the Specimens from Extrapulmonary Tuberculosis. Tuberc Respir Dis (Seoul) 2012; 72:475-80. [PMID: 23101013 PMCID: PMC3475457 DOI: 10.4046/trd.2012.72.6.475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Revised: 04/09/2012] [Accepted: 05/18/2012] [Indexed: 11/24/2022] Open
Abstract
Background Pyrazinamide (PZA) is an effective antitubercular drug that becomes toxic to Mycobacterium tuberculosis when converted to pyrazinoic acid by pyrazinamidase (PZase), encoded by mycobacterial pncA. A strong association was noted between the loss of PZase activity and PZA resistance. The causative organisms in extrapulmonary tuberculosis are rarely cultured and isolated. To detect pncA mutations in specimens from extrapulmonary tuberculosis as confirmative diagnosis of mycobacterial infection and alternative susceptibility test to PZA. Methods Specimens were collected from clinically proven extrapulmonary tuberculosis. pncA was sequenced and compared with wild-type pncA. Results pncA from 30 specimens from 23 donors were successfully amplified (56.6% in specimens, 59% in donors). Six mutations in pncA were detected (20.0% in amplified specimens, 26.1% in specimen donors) at nucleotide positions of 169, 248 and 419. The mutation at position 169 results in substitution of aspartic acid for histidine, a possible allelic variation of M. bovis that have intrinsic PZA resistance. The mutation at position 248 changes proline into arginine and that at position 419, arginine into histidine. Conclusion DNA-based diagnosis using pncA may be simultaneously useful for the early diagnosis of mycobacterial infection and the rapid susceptibility to PZA in extrapulmonary tuberculosis. A potential implication of pncA allelic variation at 169 might be suggested as a rapid diagnostic test for M. bovis infection or Bacille Calmette-Guérin (BCG) reactivation.
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Affiliation(s)
- Jaechun Lee
- Jeju National University School of Medicine, Jeju, Korea
| | - Yeo-Jun Yun
- Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Korea
| | - Cheah Yoke Kqueen
- Jeju National University School of Medicine, Jeju, Korea
- Department of Biomedical Science, Faculty of Medicine and Health Sciences, University Putra Malaysia, Selangor Darul Ehsan, Malaysia
| | - Jong Hoo Lee
- Jeju National University School of Medicine, Jeju, Korea
| | - Hee-Youn Kim
- Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Korea
| | - Young Ree Kim
- Jeju National University School of Medicine, Jeju, Korea
| | - Yoon-Hoh Kook
- Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul, Korea
| | - Keun Hwa Lee
- Jeju National University School of Medicine, Jeju, Korea
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Han SB, Jo Y, Yu JK, Kim Y, Park YJ. Performance Assessment of Advansure™ MDR-TB Genoblot Assay Kit for Anti-tuberculosis Drug Susceptibility Test. ACTA ACUST UNITED AC 2012. [DOI: 10.3343/lmo.2012.2.1.6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- Sang Bong Han
- Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Yongjun Jo
- Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Jin Kyung Yu
- Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Yonggoo Kim
- Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Yeon-Joon Park
- Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
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Molecular characterization of drug-resistant and -susceptible Mycobacterium tuberculosis isolated from patients with tuberculosis in Korea. Diagn Microbiol Infect Dis 2012; 72:52-61. [DOI: 10.1016/j.diagmicrobio.2011.09.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Revised: 08/12/2011] [Accepted: 09/06/2011] [Indexed: 11/22/2022]
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High-resolution melting curve analysis for rapid detection of rifampin and isoniazid resistance in Mycobacterium tuberculosis clinical isolates. J Clin Microbiol 2010; 48:3893-8. [PMID: 20844231 DOI: 10.1128/jcm.00396-10] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We evaluated high-resolution melting (HRM) curve analysis as a tool for detecting rifampin (RIF) and isoniazid (INH) resistance in Mycobacterium tuberculosis in an accurate, affordable, and rapid manner. Two hundred seventeen M. tuberculosis clinical isolates of known resistance phenotype were used. Twenty-nine known rpoB mutant DNAs, including rare mutations, were also included. Four pairs of primers were designed: rpoB-F/R (for codons 516 to 539 of rpoB), rpoB-516F/R (for codons 508 to 536 of rpoB), katG-F/R (for the codon 315 region of katG), and inhA-F/R (for the nucleotide substitution of C to T at position -15 of inhA). An HRM curve was generated for each isolate after real-time PCR differentiated the mutant from the wild-type strains. DNA sequencing of the target regions was performed to confirm the results of the HRM curve analysis. All but one of the 73 RIF-resistant (RIF-R) strains and all 124 RIF-susceptible (RIF-S) isolates were correctly identified by HRM curve analysis of rpoB. Twenty-seven of 29 known rpoB mutants were detected. In HRM curve analysis of katG and inhA, 90 INH-R strains that harbored katG or inhA mutations, or both, and all INH-S strains were correctly identified. Ten phenotypically INH-R strains not harboring katG or inhA mutations were not detected. The HRM curve analysis will be a useful method for detection of RIF and INH resistance in M. tuberculosis in a rapid, accurate, simple, and cost-effective manner.
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