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Quantitative drug susceptibility testing for Mycobacterium tuberculosis using unassembled sequencing data and machine learning. PLoS Comput Biol 2024; 20:e1012260. [PMID: 39102420 PMCID: PMC11326700 DOI: 10.1371/journal.pcbi.1012260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Revised: 08/15/2024] [Accepted: 06/19/2024] [Indexed: 08/07/2024] Open
Abstract
There remains a clinical need for better approaches to rapid drug susceptibility testing in view of the increasing burden of multidrug resistant tuberculosis. Binary susceptibility phenotypes only capture changes in minimum inhibitory concentration when these cross the critical concentration, even though other changes may be clinically relevant. We developed a machine learning system to predict minimum inhibitory concentration from unassembled whole-genome sequencing data for 13 anti-tuberculosis drugs. We trained, validated and tested the system on 10,859 isolates from the CRyPTIC dataset. Essential agreement rates (predicted MIC within one doubling dilution of observed MIC) were above 92% for first-line drugs, 91% for fluoroquinolones and aminoglycosides, and 90% for new and repurposed drugs, albeit with a significant drop in performance for the very few phenotypically resistant isolates in the latter group. To further validate the model in the absence of external MIC datasets, we predicted MIC and converted values to binary for an external set of 15,239 isolates with binary phenotypes, and compare their performance against a previously validated mutation catalogue, the expected performance of existing molecular assays, and World Health Organization Target Product Profiles. The sensitivity of the model on the external dataset was greater than 90% for all drugs except ethionamide, clofazimine and linezolid. Specificity was greater than 95% for all drugs except ethambutol, ethionamide, bedaquiline, delamanid and clofazimine. The proposed system can provide quantitative susceptibility phenotyping to help guide antimicrobial therapy, although further data collection and validation are required before machine learning can be used clinically for all drugs.
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Ko SJ, Yoon KH, Lee SH. Performance of the BD MAX MDR-TB assay in a clinical setting and its impact on the clinical course of patients with pulmonary tuberculosis: a retrospective before-after study. JOURNAL OF YEUNGNAM MEDICAL SCIENCE 2024; 41:113-119. [PMID: 38576340 DOI: 10.12701/jyms.2024.00024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Accepted: 03/06/2024] [Indexed: 04/06/2024]
Abstract
BACKGROUND Missing isoniazid (INH) resistance during tuberculosis (TB) diagnosis can worsen the outcomes of INH-resistant TB. The BD MAX MDR-TB assay (BD MAX) facilitates the rapid detection of TB and INH and rifampin (RIF) resistance; however, data related to its performance in clinical setting remain limited. Moreover, its effect on treatment outcomes has not yet been studied. METHODS We compared the performance of BD MAX for the detection of INH/RIF resistances to that of the line probe assay (LPA) in patients with pulmonary TB (PTB), using the results of a phenotypic drug sensitivity test as a reference standard. The treatment outcomes of patients who used BD MAX were compared with those of patients who did not. RESULTS Of the 83 patients included in the study, the BD MAX was used for an initial PTB diagnosis in 39 patients. The sensitivity of BD MAX for detecting PTB was 79.5%. The sensitivity and specificity of BD MAX for INH resistance were both 100%, whereas these were 50.0% and 95.8%, respectively, for RIF resistance. The sensitivity and specificity of BD MAX were comparable to those of LPA. The BD MAX group had a shorter time interval from specimen request to the initiation of anti-TB drugs (2.0 days vs. 5.5 days, p=0.001). CONCLUSION BD MAX showed comparable performance to conventional tests for detecting PTB and INH/RIF resistances. The implementation of BD MAX as a diagnostic tool for PTB resulted in a shorter turnaround time for the initiation of PTB treatment.
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Affiliation(s)
- Sung Jun Ko
- Department of Internal Medicine, Wonkwang University Sanbon Hospital, Gunpo, Korea
| | - Kui Hyun Yoon
- Department of Laboratory Medicine, Wonkwang University Sanbon Hospital, Gunpo, Korea
| | - Sang Hee Lee
- Department of Internal Medicine, Wonkwang University Sanbon Hospital, Gunpo, Korea
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Zhang X, He X, Zhang Y, Chen L, Pan Z, Huang Y, Li H. A new method for the detection of Mycobacterium tuberculosis based on the CRISPR/Cas system. BMC Infect Dis 2023; 23:680. [PMID: 37821806 PMCID: PMC10568934 DOI: 10.1186/s12879-023-08656-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 09/28/2023] [Indexed: 10/13/2023] Open
Abstract
OBJECT Mycobacterium tuberculosis (MTB) is a bacterium that can cause zoonoses by aerosol transmission. Tuberculosis (TB) caused by MTB heavily burdens world public health security. Developing efficient, specific, convenient, and inexpensive MTB assays are essential for preventing and controlling TB. METHODS In this study, we established a specific detection method for MTB using the Clustered Regularly Interspersed Short Palindromic Repeats (CRISPR) system, combined with recombinase mediated isothermal nucleic acid amplification (RAA) to improve the sensitivity of the detection system and achieve "two-level" amplification of the detection signal. The sensitivity and specificity of RAA combined with the CRISPR/Cas system were analyzed. Using BACTEC 960 culture as the gold standard for detecting MTB, we established the TB-CRISPR technique by testing 504 samples from patients with suspected TB. RESULTS MTB H37Ra could be seen as low as 3.13 CFU/mL by the CRISPR-Cas12a system targeting IS6110. With BACTEC960 culture (120 positives and 384 negatives) as the gold standard, the sensitivity of the TB-CRISPR technique was 0.883 (0.809-0.932), and the specificity was 0.940 (0.910-0.961). According to the receiver operating characteristic (ROC) curve analysis, the area under the curve (AUC) reached 0.944 (0.914-0.975) within 95% CI. The positive likelihood ratio (PLR) was 14.747 (9.870-22.035), and the negative likelihood ratio (NLR) was 0.124 (0.076-0.203). The positive predictive value (PPV) was 0.822 (0.742-0.881), and the negative predictive value (NPV) was 0.963 (0.937-0.979). CONCLUSION TB-CRISPR plays an essential role in the molecular diagnosis of TB. The whole detection time is less than 1.5 h. It is easy to operate and does not need complex instruments. It is of great significance for the rapid detection of MTB and the clinical diagnosis of TB.
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Affiliation(s)
- Xiaoyu Zhang
- Department of Medical Laboratory, Weifang Medical University, Weifang, 261041, Shandong, China
| | - Xiaoying He
- Department of Laboratory Medicine, the Second People's Hospital of Weifang 261041, Weifang, 261041, Shandong, China
| | - Yubo Zhang
- Department of Medical Laboratory, Weifang Medical University, Weifang, 261041, Shandong, China
| | - Lei Chen
- Department of Laboratory Medicine, the Second People's Hospital of Weifang 261041, Weifang, 261041, Shandong, China
| | - Zhaobao Pan
- Department of Laboratory Medicine, the Second People's Hospital of Weifang 261041, Weifang, 261041, Shandong, China
| | - Yueying Huang
- Department of Laboratory Medicine, Peking University Shenzhen Hospital, Shenzhen, China
| | - Heng Li
- Department of Medical Laboratory, Weifang Medical University, Weifang, 261041, Shandong, China.
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Syed RR, Catanzaro DG, Colman RE, Cooney CG, Linger Y, Kukhtin AV, Holmberg RC, Norville R, Crudu V, Ciobanu N, Codreanu A, Seifert M, Hillery N, Chiles P, Catanzaro A, Rodwell TC. Clinical Evaluation of the XDR-LFC Assay for the Molecular Detection of Isoniazid, Rifampin, Fluoroquinolone, Kanamycin, Capreomycin, and Amikacin Drug Resistance in a Prospective Cohort. J Clin Microbiol 2023; 61:e0147822. [PMID: 36757183 PMCID: PMC10035299 DOI: 10.1128/jcm.01478-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Accepted: 01/11/2023] [Indexed: 02/10/2023] Open
Abstract
While the goal of universal drug susceptibility testing has been a key component of the WHO End TB Strategy, in practice, this remains inaccessible to many. Rapid molecular tests for tuberculosis (TB) and antituberculosis drug resistance could significantly improve access to testing. In this study, we evaluated the accuracy of the Akonni Biosystems XDR-TB (extensively drug-resistant TB) TruArray and lateral-flow-cell (XDR-LFC) assay (Akonni Biosystems, Inc., Frederick, MD, USA), a novel assay that detects mutations in seven genes associated with resistance to antituberculosis drugs: katG, the inhA promoter, and the ahpC promoter for isoniazid; rpoB for rifampin; gyrA for fluoroquinolones; rrs and the eis promoter for kanamycin; and rrs for capreomycin and amikacin. We evaluated assay performance using direct sputum samples from 566 participants recruited in a prospective cohort in Moldova over 2 years. The sensitivity and specificity against the phenotypic reference were both 100% for isoniazid, 99.2% and 97.9% for rifampin, 84.8% and 99.1% for fluoroquinolones, 87.0% and 84.1% for kanamycin, 54.3% and 100% for capreomycin, and 79.2% and 100% for amikacin, respectively. Whole-genome sequencing data for a subsample of 272 isolates showed 95 to 99% concordance with the XDR-LFC-reported suspected mutations. The XDR-LFC assay demonstrated a high level of accuracy for multiple drugs and met the WHO's minimum target product profile criteria for isoniazid and rifampin, while the sensitivity for fluoroquinolones and amikacin fell below target thresholds, likely due to the absence of a gyrB target in the assay. With optimization, the XDR-LFC shows promise as a novel near-patient technology to rapidly diagnose drug-resistant tuberculosis.
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Affiliation(s)
- Rehan R Syed
- Department of Medicine, University of California, San Diego, La Jolla, California, USA
| | - Donald G Catanzaro
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas, USA
| | - Rebecca E Colman
- Department of Medicine, University of California, San Diego, La Jolla, California, USA
| | | | | | | | | | | | - Valeriu Crudu
- Phthisiopneumology Institute, Chișinău, Republic of Moldova
| | - Nelly Ciobanu
- Phthisiopneumology Institute, Chișinău, Republic of Moldova
| | | | - Marva Seifert
- Department of Medicine, University of California, San Diego, La Jolla, California, USA
| | - Naomi Hillery
- Herbert Wertheim School of Public Health and Human Longevity Science, University of California, San Diego, La Jolla, California, USA
| | - Peter Chiles
- Department of Medicine, University of California, San Diego, La Jolla, California, USA
| | - Antonino Catanzaro
- Department of Medicine, University of California, San Diego, La Jolla, California, USA
| | - Timothy C Rodwell
- Department of Medicine, University of California, San Diego, La Jolla, California, USA
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Pillay S, de Vos M, Derendinger B, Streicher EM, Dolby T, Scott LA, Steinhobel AD, Warren RM, Theron G. Non-actionable Results, Accuracy, and Effect of First- and Second-line Line Probe Assays for Diagnosing Drug-Resistant Tuberculosis, Including on Smear-Negative Specimens, in a High-Volume Laboratory. Clin Infect Dis 2023; 76:e920-e929. [PMID: 35788278 PMCID: PMC7614164 DOI: 10.1093/cid/ciac556] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 06/23/2022] [Accepted: 06/30/2022] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Rapid tuberculosis (TB) drug susceptibility testing (DST) is crucial. Genotype MTBDRsl is a widely deployed World Health Organization (WHO)-endorsed assay. Programmatic performance data, including non-actionable results from smear-negative sputum, are scarce. METHODS Sputa from Xpert MTB/RIF individuals (n = 951) were routinely-tested using Genotype MTBDRplus and MTBDRsl (both version 2). Phenotypic DST was the second-line drug reference standard. Discrepant results underwent Sanger sequencing. FINDINGS 89% (849 of 951) of individuals were culture-positive (56%, 476 of 849 smear-negative). MTBDRplus had at least 1 nonactionable result (control and/or TB-detection bands absent or invalid, precluding resistance reporting) in 19% (92 of 476) of smear-negatives; for MTBDRsl, 40% (171 of 427) were nonactionable (28%, 120 of 427 false-negative TB; 17%, 51 of 427 indeterminate). In smear-negatives, MTBDRsl sensitivity for fluoroquinolones was 84% (95% confidence interval, 67%-93), 81% (54%-95%) for second-line injectable drugs, and 57% (28%-82%) for both. Specificities were 93% (89%-98%), 88% (81%-93%), and 97% (91%-99%), respectively. Twenty-three percent (172 of 746) of Xpert rifampicin-resistant specimens were MTBDRplus isoniazid-susceptible. Days-to-second-line-susceptibility reporting with the programmatic advent of MTBDRsl improved (6 [5-7] vs 37 [35-46]; P < .001). CONCLUSIONS MTBDRsl did not generate a result in 4 of 10 smear-negatives, resulting in substantial missed resistance. However, if MTBDRsl generates an actionable result, that is accurate in ruling-in resistance. Isoniazid DST remains crucial. This study provides real-world, direct, second-line susceptibility testing performance data on non-actionable results (that, if unaccounted for, cause an overestimation of test utility), accuracy, and care cascade impact.
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Affiliation(s)
- Samantha Pillay
- DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research, South African Medical Research Council Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Stellenbosch, South Africa
- National Health Laboratory Services, Green Point, Cape Town, South Africa
| | - Margaretha de Vos
- DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research, South African Medical Research Council Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Stellenbosch, South Africa
| | - Brigitta Derendinger
- DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research, South African Medical Research Council Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Stellenbosch, South Africa
| | - Elizabeth Maria Streicher
- DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research, South African Medical Research Council Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Stellenbosch, South Africa
| | - Tania Dolby
- National Health Laboratory Services, Green Point, Cape Town, South Africa
| | - Leeré Ann Scott
- DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research, South African Medical Research Council Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Stellenbosch, South Africa
| | - Amy Debra Steinhobel
- DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research, South African Medical Research Council Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Stellenbosch, South Africa
| | - Rob Mark Warren
- DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research, South African Medical Research Council Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Stellenbosch, South Africa
| | - Grant Theron
- DSI-NRF Centre of Excellence for Biomedical Tuberculosis Research, South African Medical Research Council Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Stellenbosch, South Africa
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Chung ES, Johnson WC, Aldridge BB. Types and functions of heterogeneity in mycobacteria. Nat Rev Microbiol 2022; 20:529-541. [PMID: 35365812 DOI: 10.1038/s41579-022-00721-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/01/2022] [Indexed: 12/24/2022]
Abstract
The remarkable ability of Mycobacterium tuberculosis to survive attacks from the host immune response and drug treatment is due to the resilience of a few bacilli rather than a result of survival of the entire population. Maintenance of mycobacterial subpopulations with distinct phenotypic characteristics is key for survival in the face of dynamic and variable stressors encountered during infection. Mycobacterial populations develop a wide range of phenotypes through an innate asymmetric growth pattern and adaptation to fluctuating microenvironments during infection that point to heterogeneity being a vital survival strategy. In this Review, we describe different types of mycobacterial heterogeneity and discuss how heterogeneity is generated and regulated in response to environmental cues. We discuss how this heterogeneity may have a key role in recording memory of their environment at both the single-cell level and the population level to give mycobacterial populations plasticity to withstand complex stressors.
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Affiliation(s)
- Eun Seon Chung
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
| | - William C Johnson
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA.,Tufts University School of Graduate Biomedical Sciences, Boston, MA, USA
| | - Bree B Aldridge
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA. .,Tufts University School of Graduate Biomedical Sciences, Boston, MA, USA. .,Stuart B. Levy Center for Integrated Management of Antimicrobial Resistance, Tufts University, Boston, MA, USA. .,Department of Biomedical Engineering, Tufts University School of Engineering, Medford, MA, USA.
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Bigio J, van Gemert W, Kaiser B, Waning B, Pai M. Asia emerges as a hotbed of diagnostic innovations for tuberculosis. J Clin Tuberc Other Mycobact Dis 2021; 25:100267. [PMID: 34485710 PMCID: PMC8408512 DOI: 10.1016/j.jctube.2021.100267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Jacob Bigio
- Research Institute of the McGill University Health Centre, Montreal, Canada
- McGill International TB Centre, Montreal, Canada
| | | | | | | | - Madhukar Pai
- McGill International TB Centre, Montreal, Canada
- Dept of Epidemiology and Biostatistics, McGill University, Montreal, Canada
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de Vos M, Scott L, David A, Trollip A, Hoffmann H, Georghiou S, Carmona S, Ruhwald M, Stevens W, Denkinger CM, Schumacher SG. Comparative Analytical Evaluation of Four Centralized Platforms for the Detection of Mycobacterium tuberculosis Complex and Resistance to Rifampicin and Isoniazid. J Clin Microbiol 2021; 59:e02168-20. [PMID: 33268535 PMCID: PMC8106716 DOI: 10.1128/jcm.02168-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Accepted: 11/21/2020] [Indexed: 01/25/2023] Open
Abstract
Failure to rapidly identify drug-resistant tuberculosis (TB) increases the risk of patient mismanagement, the amplification of drug resistance, and ongoing transmission. We generated comparative analytical data for four automated assays for the detection of TB and multidrug-resistant TB (MDR-TB): Abbott RealTime MTB and MTB RIF/INH (Abbott), Hain Lifescience FluoroType MTBDR (Hain), BD Max MDR-TB (BD), and Roche cobas MTB and MTB-RIF/INH (Roche). We included Xpert MTB/RIF (Xpert) and GenoType MTBDRplus as comparators for TB and drug resistance detection, respectively. We assessed analytical sensitivity for the detection of the Mycobacterium tuberculosis complex using inactivated strains (M. tuberculosis H37Rv and M. bovis) spiked into TB-negative sputa and computed the 95% limits of detection (LOD95). We assessed the accuracy of rifampicin and isoniazid resistance detection using well-characterized M. tuberculosis strains with high-confidence mutations accounting for >85% of first-line resistance mechanisms globally. For H37Rv and M. bovis, we measured LOD95 values of 3,781 and 2,926 (Xpert), 322 and 2,182 (Abbott), 826 and 4,301 (BD), 10,398 and 23,139 (Hain), and 2,416 and 2,136 (Roche) genomes/ml, respectively. Assays targeting multicopy genes or targets (Abbott, BD, and Roche) showed increased analytical sensitivity compared to Xpert. Quantification of the panel by quantitative real-time PCR prevents the determination of absolute values, and results reported here can be interpreted for comparison purposes only. All assays showed accuracy comparable to that of Genotype MTBDRplus for the detection of rifampicin and isoniazid resistance. The data from this analytical study suggest that the assays may have clinical performances similar to those of WHO-recommended molecular TB and MDR-TB assays.
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Affiliation(s)
| | - Lesley Scott
- Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Anura David
- Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Andre Trollip
- Foundation for Innovative New Diagnostics, Geneva, Switzerland
| | - Harald Hoffmann
- Institute of Microbiology and Laboratory Medicine, Department IML Red GmbH, WHO-Supranational Reference Laboratory of Tuberculosis, Munich-Gauting, Germany
- SYNLAB Gauting, SYNLAB Human Genetics Munich, Munich-Gauting, Germany
| | | | - Sergio Carmona
- Foundation for Innovative New Diagnostics, Geneva, Switzerland
| | - Morten Ruhwald
- Foundation for Innovative New Diagnostics, Geneva, Switzerland
| | - Wendy Stevens
- Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- National Health Laboratory Services, Johannesburg, South Africa
| | - Claudia M Denkinger
- Foundation for Innovative New Diagnostics, Geneva, Switzerland
- Division of Tropical Medicine, Center of Infectious Diseases, University Hospital of Heidelberg, Heidelberg, Germany
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Cao Y, Parmar H, Gaur RL, Lieu D, Raghunath S, Via N, Battaglia S, Cirillo DM, Denkinger C, Georghiou S, Kwiatkowski R, Persing D, Alland D, Chakravorty S. Xpert MTB/XDR: a 10-Color Reflex Assay Suitable for Point-of-Care Settings To Detect Isoniazid, Fluoroquinolone, and Second-Line-Injectable-Drug Resistance Directly from Mycobacterium tuberculosis-Positive Sputum. J Clin Microbiol 2021; 59:e02314-20. [PMID: 33298611 PMCID: PMC8106700 DOI: 10.1128/jcm.02314-20] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 11/22/2020] [Indexed: 11/20/2022] Open
Abstract
We describe the design, development, analytical performance, and a limited clinical evaluation of the 10-color Xpert MTB/XDR assay (CE-IVD only, not for sale in the United States). This assay is intended as a reflex test to detect resistance to isoniazid (INH), fluoroquinolones (FLQ), ethionamide (ETH), and second-line injectable drugs (SLIDs) in unprocessed sputum samples and concentrated sputum sediments which are positive for Mycobacterium tuberculosis The Xpert MTB/XDR assay simultaneously amplifies eight genes and promoter regions in M. tuberculosis and analyzes melting temperatures (Tm s) using sloppy molecular beacon (SMB) probes to identify mutations associated with INH, FLQ, ETH, and SLID resistance. Results can be obtained in under 90 min using 10-color GeneXpert modules. The assay can differentiate low- versus high-level resistance to INH and FLQ as well as cross-resistance versus individual resistance to SLIDs by identifying mutation-specific Tm s or Tm patterns generated by the SMB probes. The assay has a limit of detection comparable to that of the Xpert MTB/RIF assay and successfully detected 16 clinically significant mutations in a challenge set of clinical isolate DNA. In a clinical study performed at two sites with 100 sputum and 214 clinical isolates, the assay showed a sensitivity of 94% to 100% and a specificity of 100% for all drugs except for ETH compared to that of sequencing. The sensitivity and specificity were in the same ranges as those of phenotypic drug-susceptibility testing. Used in combination with a primary tuberculosis diagnostic test, this assay should expand the capacity for detection of drug-resistant tuberculosis near the point of care.
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Affiliation(s)
- Yuan Cao
- New Jersey Medical School, Rutgers University, Newark, New Jersey, USA
| | - Heta Parmar
- New Jersey Medical School, Rutgers University, Newark, New Jersey, USA
| | | | | | | | - Nova Via
- Cepheid Inc., Sunnyvale, California, USA
| | | | | | | | | | | | | | - David Alland
- New Jersey Medical School, Rutgers University, Newark, New Jersey, USA
| | - Soumitesh Chakravorty
- New Jersey Medical School, Rutgers University, Newark, New Jersey, USA
- Cepheid Inc., Sunnyvale, California, USA
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