Diagnosis of multidrug-resistant tuberculosis and extensively drug-resistant tuberculosis: Current standards and challenges

Multidrug-resistant tuberculosis

One of predominant contributors to global mortality is tuberculosis (TB), an infection caused by Mycobacterium tuberculosis (MTB). Inappropriate and ineffectual treatment can lead to the development of drug-resistant TB. One of the most common forms of drug-resistant TB is multidrug-resistant tuberculosis (MDR-TB), caused by mutations in the rpoB and katG genes that lead to resistance to anti-TB drugs, rifampicin (RIF) and isoniazid (INH), respectively. Although culturing remains the gold standard, it is not rapid thereby delaying potential treatment and potentially increasing the incidence of MDR-TB. In contrast, molecular techniques provide a highly sensitive and specific alternative. This review discusses the classification of biomarkers used to detect MDR-TB, some of the commonly used anti-TB drugs, and DNA mutations in MTB that lead to anti-TB resistance. The objective of this review is to increase awareness of the need for rapid and precise detection of MDR-TB cases to decrease morbidity and mortality of this infectious disease worldwide.

Rapid Diagnosis of Drug-Resistant Tuberculosis-Opportunities and Challenges

Global tuberculosis (TB) eradication is undermined by increasing prevalence of emerging resistance to available drugs, fuelling ongoing demand for more complex diagnostic and treatment strategies. Early detection of TB drug resistance coupled with therapeutic decision making guided by rapid characterisation of pre-treatment and treatment emergent resistance remains the most effective strategy for averting Drug-Resistant TB (DR-TB) transmission, reducing DR-TB associated mortality, and improving patient outcomes. Solid- and liquid-based mycobacterial culture methods remain the gold standard for Mycobacterium tuberculosis (MTB) detection and drug susceptibility testing (DST). Unfortunately, delays to result return, and associated technical challenges from requirements for specialised resource and capacity, have limited DST use and availability in many high TB burden resource-limited countries. There is increasing availability of a variety of rapid nucleic acid-based diagnostic assays with adequate sensitivity and specificity to detect gene mutations associated with resistance to one or more drugs. While a few of these assays produce comprehensive calls for resistance to several first- and second-line drugs, there is still no endorsed genotypic drug susceptibility test assay for bedaquiline, pretomanid, and delamanid. The global implementation of regimens comprising these novel drugs in the absence of rapid phenotypic drug resistance profiling has generated a new set of diagnostic challenges and heralded a return to culture-based phenotypic DST. In this review, we describe the available tools for rapid diagnosis of drug-resistant tuberculosis and discuss the associated opportunities and challenges.

Crystal violet decolorization assay: a simplified colorimetric test for the rapid detection of multidrug-resistant Mycobacterium tuberculosis isolates

The increased prevalence of multi-drug resistant M. tuberculosis is quite possibly the direst and most difficult task for the early diagnosis and treatment. A rapid, reliable, and inexpensive diagnostic method is the need of the hour. The current study on crystal violet decolorization assay explores the possibility to develop a rapid and simple detection method to detect multi-drug-resistant tuberculosis isolates by comparing the results with the traditional liquid culture drug susceptibility testing method based on their sensitivity, specificity, positive predictive value, and negative predictive value. 70 isolates were used for the study and were detected as multi-drug resistant, mono drug-resistant, and sensitive by using crystal violet decolourization assay and further compared with the results of DST and using H37Rv as the standard control strain. The sensitivity, specificity, positive predictive value, and negative predictive value of crystal violet decolorization assay (Rifampicin: 100%, 94.60%, 100% and 82.40%; isoniazid: 100%, 94.10%, 100%, 86.40%) are calculated and the percentage were compared with the conventional liquid culture drug susceptibility testing for M. tuberculosis using rifampicin and isoniazid. Crystal violet decolourization assay is rapid, reproducible, and doesn't require any highly experienced personal or sophisticated laboratory instruments for interpretation. This assay is found to be nearly as reliable as conventional liquid culture drug susceptibility testing and may thus be of great help in phenotypic confirmation of multi-drug resistant tuberculosis by providing results more rapidly.

An Insight into Advances in Developing Nanotechnology Based Therapeutics, Drug Delivery, Diagnostics and Vaccines: Multidimensional Applications in Tuberculosis Disease Management

Tuberculosis (TB), one of the deadliest contagious diseases, is a major concern worldwide. Long-term treatment, a high pill burden, limited compliance, and strict administration schedules are all variables that contribute to the development of MDR and XDR tuberculosis patients. The rise of multidrug-resistant strains and a scarcity of anti-TB medications pose a threat to TB control in the future. As a result, a strong and effective system is required to overcome technological limitations and improve the efficacy of therapeutic medications, which is still a huge problem for pharmacological technology. Nanotechnology offers an interesting opportunity for accurate identification of mycobacterial strains and improved medication treatment possibilities for tuberculosis. Nano medicine in tuberculosis is an emerging research field that provides the possibility of efficient medication delivery using nanoparticles and a decrease in drug dosages and adverse effects to boost patient compliance with therapy and recovery. Due to their fascinating characteristics, this strategy is useful in overcoming the abnormalities associated with traditional therapy and leads to some optimization of the therapeutic impact. It also decreases the dosing frequency and eliminates the problem of low compliance. To develop modern diagnosis techniques, upgraded treatment, and possible prevention of tuberculosis, the nanoparticle-based tests have demonstrated considerable advances. The literature search was conducted using Scopus, PubMed, Google Scholar, and Elsevier databases only. This article examines the possibility of employing nanotechnology for TB diagnosis, nanotechnology-based medicine delivery systems, and prevention for the successful elimination of TB illnesses.

Innovations in Molecular Identification of Mycobacterium tuberculosis

Tuberculosis (TB) continues to be a significant public health concern on a global scale. Quick and precise identification of Mycobacterium tuberculosis (MTB) in symptomatic patients is pivotal for worldwide TB eradication initiatives. As an infectious disorder induced by MTB, it remains a critical threat to public health, particularly in poor countries, due to an inadequate diagnostic research laboratory. There is a need for a persistent incentive to reduce response time for effective diagnosis and control of TB infection, which is a benefit that molecular techniques provide over traditional methods. Although there is a tremendous overall prevalence of TB and a relatively poor probability of case identification worldwide. Common screening techniques have focused on tests that have many fundamental shortcomings. Due to the development of antibiotic-resistant Mycobacterium strains, TB is one of the leading contributors to fatalities. It is now possible to examine TB using molecular detection techniques, which are faster and more cost-effective than previous methods, such as standard culture procedures to test and verify antibiotic resistance in patients with TB. Whole genome sequencing (WGS), faster nucleic acid amplification tests, has made it easier to diagnose and treat TB more quickly. This article addresses the genetic approaches for detecting Mycobacterium tuberculosis complex (MTBC) in clinical specimens as well as antibiotic resistance in mycobacterium and discusses the practical limitations of using these methods.

Evaluation of Accuracy of Microplate Alamar Blue Assay and Proportion Method for Prompt Detection of Mycobacterium tuberculosis and Clinical Isolates of Multidrug-resistant M. tuberculosis

Background: Tuberculosis is appraised to cause the deaths of more than a billion people in the last decades. Objectives: The current study compares the performance of microplate Alamar blue assay for clinical isolates of Mycobacterium tuberculosis and multidrug-resistant tuberculosis. Microplate Alamar blue assay was performed in a central tuberculosis laboratory at Golestan University of Medical Sciences in Gorgan, Iran. Methods: In the first step, the microplate Alamar blue assay was used for the detection of 78 clinical isolates in the Golestan regional tuberculosis reference laboratory, and the results were compared with those of the proportion assay. In the second step, the microplate Alamar blue assay and the proportion assay were used for the drug-susceptibility of 35 isolates. Results: In the microplate Alamar blue assay, the sensitivity was 100 (90.97 - 100), with a specificity of 74.36 (57.87 - 86.96), positive predictive value of 79.59 (65.66 - 89.76), and negative predictive value of 100 (88.06 - 100). For the microplate Alamar blue assay with rifampin, the sensitivity was 100 (89.11 - 100), specificity was 100 (29.24 - 100), positive predictive value was 100 (89.11 - 100), and negative predictive value was 100 (29.24 - 100). For the microplate Alamar blue assay with isoniazid, the sensitivity was 84.38 (67.21 - 94.72), specificity was 66.67 (9.43 - 99.16), positive predictive value was 96.43 (81.65 - 99.91), and negative predictive value was 28.57 (3.67 - 70.96). Conclusions: We found high accuracy between the microplate Alamar blue assay with rifampin and the proportion assay. The rapid and low-cost microplate Alamar blue assay is an inexpensive and appropriate assay for the detection of rifampin-resistant tuberculosis in low-income countries.

Multidrug-resistant tuberculosis in Imo State, Southeast, Nigeria

Background

Multidrug-resistant tuberculosis (MDR-TB) is a global health challenge. The emergence of MDR TB has contributed remarkably to the spread of tuberculosis and also poses a threat, which if not effectively addressed may wipe out the achievements of previous efforts in controlling tuberculosis.

Objective

This study was aimed at detecting MDR-TB among patients in a setting prevalent with tuberculosis and HIV in Southeast, Nigeria.

Method

Sputum specimens collected from 740 suspected tuberculosis (TB) patients were screened for acid-fast bacilli (AFB). All the 111 AFB positive samples were subjected to culture on Lowenstein-Jensen (LJ) medium and Mycobacterium Growth Indicator Tube (MGIT) 960 TB system. The isolates were then confirmed as Mycobacterium tuberculosis using SD Bioline Rapid Diagnostic Tests before being subjected to drug susceptibility testing to first-line anti-TB drugs. MDR-TB was determined by isolates being resistant to both isoniazid and rifampicin. HIV testing was performed for participants included in the study using standard rapid diagnostic tests.

Result

Out of the 111 AFB-positive sputum samples, 65 (58.6%) were culture-positive for Mycobacterium tuberculosis. MDR-TB was found in 2 ([3.1%] 95% CI = 0.0-7.3) of the culture-positive samples. The rate of TB and HIV coinfection was 7.7%. Maximum single-drug resistance was seen in ethambutol 12 ([18.5%] 95% CI = 9.0-27.9).

Conclusion

The MDR-TB rate of 3.1% found in this study was relatively low and efforts should be intensified to keep it low.

Discordant line probe genotypic testing vs culture-based drug susceptibility phenotypic testing in TB endemic KwaZulu-Natal: Impact on bedside clinical decision making

The recommendations for Mycobacterium tuberculosis drug susceptibility testing include both phenotypic and genotypic methods. This concurrent use of differing testing platforms has created an emerging challenge of discordant results, creating a diagnostic dilemma for the laboratorians as well as attending clinicians. We undertook a retrospective study to determine the prevalence of discordant results between the MTBDRplus line probe assay and solid culture-based drug susceptibility testing for rifampicin and isoniazid. The analysis was conducted for the period January 2013 and December 2015 at the Inkosi Albert Luthuli Central Hospital. Rifampicin and isoniazid resistance testing data were "paired" on 8273 isolates for culture-based drug susceptibility testing and line probe assay. The latter method showed high sensitivity and specificity of 93% and 95% respectively for isoniazid testing. For rifampicin testing, sensitivity and specificity were 95% and 75%. Overall, discordance was 14.6% for rifampicin and 7.2% for isoniazid. This report is not intended to determine superiority of one method over another. It is merely to show that discordance does exist between different methods of testing. Given the burden of HIV and Tuberculosis in Sub-Saharan Africa, these findings have clinical significance and huge public health implications. Clinicians should understand the limitations of phenotypic testing methods.

Low prevalence of MDR-TB in Lao PDR: results from the first national anti-tuberculosis drug resistance survey

OBJECTIVE

To present results of the first national anti-tuberculosis (TB) drug resistance survey conducted in Lao PDR between May 2016 and August 2017 to determine the prevalence of resistance to first-line anti-TB drugs among new and previously treated pulmonary TB cases in the country.

METHODS

Patients with sputum smear-positive pulmonary TB were enrolled from 42 TB laboratories distributed in 40 clusters throughout the country. Survey sites were selected using probability-proportional-to-size sampling among all diagnostic centres in the country. In addition to smear microscopy, all patients underwent Xpert MTB/RIF testing and those found positive to Mycobacterium tuberculosis underwent sputum culture and drug susceptibility testing using the proportion method on solid Löwenstein-Jensen medium.

RESULTS

Among 1006 eligible patients, 946 sputum smear-positive and Xpert MTB/RIF positive (Mycobacterium tuberculosis detected) patients were included in the survey, comprising 897 new and 49 previously treated TB cases. The prevalence of rifampicin-resistant TB was 1.2% (95% CI: 0.5-2.0%, n = 11/897) among new cases and 4.1% (95% CI: 0-9.6%, n = 2/49) among previously treated cases. Among the 946 TB cases confirmed by Xpert MTB/RIF, phenotypic drug sensitivity testing was available for 820 (776 new and 44 previously treated). The prevalence of multidrug-resistant TB (MDR-TB) was 0.5% (95% CI: 0-1.0%, n = 4/776) among new cases and 2.3% (95% CI: 0-6.7%, n = 1/44) among previously treated cases. No resistance to second-line injectable agents nor to fluoroquinolones was detected among MDR-TB patients.

CONCLUSIONS

The first national anti-TB drug resistance survey in Lao PDR demonstrated an encouragingly low prevalence of MDR-TB. The results appear lower than previous WHO estimates, and in line with the routine surveillance based on Xpert MTB/RIF testing (conducted among 50% of presumptive TB patients in 2017). The country should continue to expand its Xpert MTB/RIF network and strive to achieve universal drug susceptibility testing.

Sentinel Amenable Mortality: A New Way to Assess the Quality of Healthcare by Examining Causes of Premature Death for Which Highly Efficacious Medical Interventions Are Available

BACKGROUND

Amenable mortality, or premature deaths that could be prevented with medical care, is a proven indicator for assessing healthcare quality when adapted to a country or region's specific healthcare context. This concept is currently used to evaluate the performance of national and international healthcare systems. However, the levels of efficacy and effectiveness determined using this indicator can vary greatly depending on the causes of death that are included. We introduce a new approach by identifying a subgroup of causes for which there are available treatments with a high level of efficacy. These causes should be considered sentinel events to help identify limitations in the effectiveness and quality of health provision.

METHODS

We conducted an extensive literature review using a list of amenable causes of death compiled by Spanish researchers. We complemented this approach by assessing the time trends of amenable mortality in two high-income countries that have a similar quality of healthcare but very different systems of provision, namely, Spain and the United States. This enabled us to identify different levels of efficacy of medical interventions (high, medium, and low). We consulted a group of medical experts and combined this information to help make the final classification of sentinel amenable causes of death.

RESULTS

Sentinel amenable mortality includes causes such as surgical conditions, thyroid diseases, and asthma. The remaining amenable causes of death either have a higher complexity in terms of the disease or need more effective medical interventions or preventative measures to guarantee early detection and adherence to treatment. These included cardiovascular diseases, diabetes, hypertension, all amenable cancers, and some infectious diseases such as pneumonia, influenza, and tuberculosis.

CONCLUSIONS

Sentinel amenable mortality could act as a good sentinel indicator to identify major deficiencies in healthcare quality and provision and detect inequalities across populations.

Prevalence of drug-resistant pulmonary tuberculosis in India: systematic review and meta-analysis

Background

Drug-resistant pulmonary tuberculosis (DR-TB) is a significant public health issue that considerably deters the ongoing TB control efforts in India. The purpose of this review was to investigate the prevalence of DR-TB and understand the regional variation in resistance pattern across India from 1995 to 2015, based on a large body of published epidemiological studies.

Methods

A systematic review of published studies reporting prevalence of DR-TB from biomedical databases (PubMed and IndMed) was conducted. Meta-analysis was performed using random effects model and the pooled prevalence estimate (95% confidence interval [CI]) of DR-TB, multidrug resistant (MDR-) TB, pre-extensively drug-resistant (pre-XDR) TB and XDR-TB were calculated across two study periods (decade 1: 1995 to 2005; decade 2: 2006 to 2015), countrywide and in different regions. Heterogeneity in this meta-analysis was assessed using I² statistic.

Results

A total of 75 of 635 screened studies that fulfilled the inclusion criteria were selected. Over 40% of 45,076 isolates suspected for resistance to any first-line anti-TB drugs tested positive. Comparative analysis revealed a worsening trend in DR-TB between the two study decades (decade 1: 37.7% [95% CI = 29.0; 46.4], n = 25 vs decade 2: 46.1% [95% CI = 39.0; 53.2], n = 36). The pooled estimate of MDR-TB resistance was higher in previously treated patients (decade 1: 29.8% [95% CI = 20.7; 39.0], n = 13; decade 2: 35.8% [95% CI = 29.2; 42.4], n = 24) as compared with the newly diagnosed cases (decade 1: 4.1% [95% CI = 2.7; 5.6], n = 13; decade 2: 5.6% [95% CI = 3.8; 7.4], n = 17). Overall, studies from Western states of India reported highest prevalence of DR-TB (57.8% [95% CI = 37.4; 78.2], n = 6) and MDR-TB (39.9% [95% CI = 21.7; 58.0], n = 6) during decade 2. Prevalence of pre-XDR TB was 7.9% (95% CI = 4.4; 11.4, n = 5) with resistance to fluoroquinolone (66.3% [95% CI = 58.2; 74.4], n = 5) being the highest. The prevalence of XDR-TB was 1.9% (95% CI = 1.2; 2.6, n = 14) over the 20-year period.

Conclusion

The alarming increase in the trend of anti-TB drug resistance in India warrants the need for a structured nationwide surveillance to assist the National TB Control Program in strengthening treatment strategies for improved outcomes.

Genetic Mimetics of Mycobacterium tuberculosis and Methicillin-Resistant Staphylococcus aureus as Verification Standards for Molecular Diagnostics

Molecular diagnostics have revolutionized the management of health care through enhanced detection of disease or infection and effective enrollment into treatment. In recognition of this, the World Health Organization approved the rollout of nucleic acid amplification technologies for identification of Mycobacterium tuberculosis using platforms such as GeneXpert MTB/RIF, the GenoType MTBDRplus line probe assay, and, more recently, GeneXpert MTB/RIF Ultra. These assays can simultaneously detect tuberculosis infection and assess rifampin resistance. However, their widespread use in health systems requires verification and quality assurance programs. To enable development of these, we report the construction of genetically modified strains of Mycobacterium smegmatis that mimic the profile of Mycobacterium tuberculosis on both the GeneXpert MTB/RIF and the MTBDRplus line probe diagnostic tests. Using site-specific gene editing, we also created derivatives that faithfully mimic the diagnostic result of rifampin-resistant M. tuberculosis, with mutations at positions 513, 516, 526, 531, and 533 in the rifampin resistance-determining region of the rpoB gene. Next, we extended this approach to other diseases and demonstrated that a Staphylococcus aureus gene sequence can be introduced into M. smegmatis to generate a positive response for the SCCmec probe in the GeneXpert SA Nasal Complete molecular diagnostic cartridge, designed for identification of methicillin-resistant S. aureus These biomimetic strains are cost-effective, have low biohazard content, accurately mimic drug resistance, and can be produced with relative ease, thus illustrating their potential for widespread use as verification standards for diagnosis of a variety of diseases.

Verification of Diagnosis in Tuberculosis: A Case Report and Discussion

Tuberculosis (TB), caused by strains of Mycobacterium tuberculosis complex (M. tuberculosis), is a pulmonary infection that is spread by airborne droplet transmission. The development and spread of drug-resistant strains of M. tuberculosisgreatly jeopardize TB control efforts. We report the case of a previously healthy 43-year-old male, visiting from China, who presented to the emergency department complaining of hemoptysis of 10 days' duration. Cultures were positive for acid fast bacteria and negative for fungi. M. tuberculosis infection was confirmed by a deoxyribonucleic acid (DNA) probe. The patient was initially started on first-line therapy of isoniazid, rifampin, pyrazinamide, and ethambutol, with pyridoxine. His country of origin, China, increased suspicion for drug-resistant tuberculosis. Two weeks later, susceptibility testing of the M. tuberculosis isolate showed resistance to isoniazid, pyrazinamide, and ethambutol. Therapy was subsequently changed to amikacin, linezolid, moxifloxacin, and rifampin. The isolate was subsequently sent to the Center for Disease Control (CDC) for evaluation. Repeat testing showed that the isolate was susceptible to rifampin, pyrazinamide, and ethambutol. The patient was then restarted on his initial anti-TB regimen and was able to return to China. The main goals for the treatment of TB are to treat the individual patient and to minimize transmission. Clues that point to the possibility of multiple drug resistant tuberculosis (MDR-TB) include contact with a patient with MDR-TB, origin from an endemic region, or failure of therapy with documented supervision. Collaboration with experts was imperative in ensuring appropriate patient care.

Current and developing therapies for the treatment of multi drug resistant tuberculosis (MDR-TB) in India

INTRODUCTION

India accounts for 25% of the global burden of MDR-TB. In 2016, the India's Revised National TB Control Programme reported a success rate of 46% among 19,298 MDR-TB patients treated under the programme. This suboptimal treatment outcome warrants an urgent need for newer drugs and newer regimens in the treatment of MDR-TB. India requires new shorter, cheap, safe and effective anti-TB regimen to treat MDR-TB. Areas covered: We used different search strategies to obtain relevant literature from PubMed, on Indian experiences of developing therapies for the treatment of MDR-TB. Further information from the Central TB Division Government of India on programmatic management of resistant TB was collected. Expert opinion: In 2016 WHO recommended a shorter MDR-TB regimen of 9-12 months (4-6 Km-Mfx-Pto-Cfz-Z-Hhigh-dose-E /5 Mfx-Cfz-Z-E) may be used instead of longer regimens. Currently, conducting trials involving newer drugs such as bedaquiline, have been proposed. The regimen will be of a shorter duration containing isoniazid, prothionamide, bedaquiline, levofloxacin, ciprofloxacin, ethambutol and pyrazinamide (STREAM regimen). To successfully treat MDR-TB one requires new classes of antibiotic and newer diagnostic tests. This represents an enormous financial and technical challenge to the programme managers and policy makers.

Extensively Drug-resistant Tuberculosis (XDR-TB): A daunting challenge to the current End TB Strategy and policy recommendations

Extensively Drug-resistant Tuberculosis (XDR-TB) has emerged as one of the most formidable challenges to the End TB Strategy that has targeted a 95% reduction in TB deaths and 90% reduction in cases by 2035. Globally, there were an estimated 55,100 new XDR-TB cases in 2015 in 117 countries. However, only one in 30 XDR-TB cases had been reported so far. Drug susceptibility test (DST) is the mainstay for diagnosing XDR-TB, but the lack of laboratory facilities in the resource-limited endemic countries limit its uses. A few new drugs including bedaquiline and delamanid, have the potential to improve the efficiency of XDR-TB treatment, but the drugs have been included in 39 countries only. The costs of XDR-TB treatment are several folds higher than that of the MDR-TB. Despite the financing from the donors, there is an urgent need to fill the current funding gap of US$ 2 billion to ensure effective treatment and robust surveillance. In the review article we have addressed current update on XDR-TB, including surveillance, diagnosis and the interventions needed to treat and limit its spread, emphasis on extensive financial support for implementing of current recommendations to meet the goals of End TB Strategy.

Prevalence and Risk Factors of Delayed Sputum Conversion among Patients Treated for Smear Positive PTB in Northwestern Rural Tanzania: A Retrospective Cohort Study

Introduction

Smear positive TB carries high morbidity and mortality. The TB treatment aims at sputum conversion by two months of antituberculous. Patients who delay sputum conversion remain potentially infectious, with risk of treatment failure, drug resistance, and mortality. Little is known about the magnitude of this problem in our setting. This study was designed to determine the prevalence and risk factors of delayed sputum conversion in northwestern rural part of Tanzania.

Methods

This was a retrospective cohort study involving smear positive TB patients at Sengerema DDH in 2015. Demographic data, HIV status, and sputum results at TB diagnosis and on TB treatment were collected and analyzed using STATA 11.

Results

In total, 156 patients were studied. Males were 97 (62%); the median age was 39 [30–51] years. Fifty-five (35.3%) patients were HIV coinfected and 13 (8.3%) patients had delayed sputum conversion which was strongly associated with male gender (OR = 8.2, p = 0.046), age >50 years (OR = 6.7, p = 0.003), and AFB 3+ (OR = 8.1, p = 0.008).

Conclusions

Delayed sputum conversion is prevalent in this study. These patients can potentially fail on treatment, develop drug resistance, and continue spreading TB. Strategies to reduce the rate of delayed sputum conversion could also reduce these potential unfavorable outcomes.

Establishment of a rapid and sensitive method based on recombinase polymerase amplification to detect mts90, a new molecular target of Mycobacterium tuberculosis

The paper is about rapid screening of tuberculosis for detecting mts90, a new molecular target ofMycobacterium tuberculosis.

eis Promoter C14G and C15G Mutations Do Not Confer Kanamycin Resistance in Mycobacterium tuberculosis

We studied the significance of particular eis mutations on Mycobacterium tuberculosis drug resistance using a specialized transduction strategy. Recombinant strains harboring eis promoter mutations C14T, C12T, and G10A exhibited kanamycin resistance with MICs of 40, 10, and 20 μg/ml, respectively, while recombinant strains harboring C14G and C15G mutations were kanamycin susceptible (MIC, 2.5 to 5 μg/ml). Each of the eis mutants tested remained amikacin susceptible (MIC, 0.5 to 4 μg/ml). The identification of specific eis mutations is needed for accurate genotypic susceptibility testing for kanamycin.

Use of RODAC plates to measure containment of Mycobacterium tuberculosis in a Class IIB biosafety cabinet during routine operations

OBJECTIVE/BACKGROUND

Guidelines for the manipulation of Mycobacterium tuberculosis (MTB) cultures require a Biosafety Level 3 (BSL-3) infrastructure and accompanying code of conduct. In this study, we aimed to validate and apply detection methods for viable mycobacteria from surfaces in a BSL-3 MTB laboratory.

METHODS

We evaluated phenotypic (Replicate Organism Detection and Counting [RODAC] plates) and molecular (propidium monoazide [PMA]-based polymerase chain reaction [PCR]) approaches for the detection of viable mycobacteria, as well as the effect of 70% ethanol applied for 5min for disinfection against mycobacteria. For validation of the method, recovery of serial dilutions of Mycobacterium bovis bacillus Calmette-Guérin from glass slides was measured. Subsequently, we stamped surfaces in and around the biosafety cabinet (BSC) after different technicians had manipulated high bacterial load suspensions for routine drug-susceptibility testing in a Class II BSC.

RESULTS

RODAC stamping could detect as few as three bacteria on slides stamped either 5min or 60min after inoculation. PMA-based PCR, tested in parallel, did not pass validation. Mycobacteria were still detected after 5-min disinfection with ethanol 70%. In the BSL-3, from 201 RODAC-stamped surfaces, MTB was detected in four: three inside a BSC-on a tube cap and on an operator's gloves-and one outside, on an operator's gown.

CONCLUSION

RODAC plates detect mycobacteria at low numbers of microorganisms. In addition, this method allowed us to show that 70% ethanol does not reliably kill mycobacteria when applied for 5min to a dried surface, and that MTB bacilli may arrive outside a Class II BSC during routine practice, although the route could not be documented.

Shortened first-line TB treatment in Brazil: potential cost savings for patients and health services

BACKGROUND

Shortened treatment regimens for tuberculosis are under development to improve treatment outcomes and reduce costs. We estimated potential savings from a societal perspective in Brazil following the introduction of a hypothetical four-month regimen for tuberculosis treatment.

METHODS

Data were gathered in ten randomly selected health facilities in Rio de Janeiro. Health service costs were estimated using an ingredient approach. Patient costs were estimated from a questionnaire administered to 126 patients. Costs per visits and per case treated were analysed according to the type of therapy: self-administered treatment (SAT), community- and facility-directly observed treatment (community-DOT, facility-DOT).

RESULTS

During the last 2 months of treatment, the largest savings could be expected for community-DOT; on average USD 17,351-18,203 and USD 43,660-45,856 (bottom-up and top-down estimates) per clinic. Savings to patients could also be expected as the median (interquartile range) patient-related costs during the two last months were USD 108 (13-291), USD 93 (36-239) and USD 11 (7-126), respectively for SAT, facility-DOT and community-DOT.

CONCLUSION

Introducing a four-month regimen may result in significant cost savings for both the health service and patients, especially the poorest. In particular, a community-DOT strategy, including treatment at home, could maximise health services savings while limiting patient costs. Our cost estimates are likely to be conservative because a 4-month regimen could hypothetically increase the proportion of patients cured by reducing the number of patients defaulting and we did not include the possible cost benefits from the subsequent prevention of costs due to downstream transmission averted and rapid clinical improvement with less side effects in the last two months.

The implications of whole-genome sequencing in the control of tuberculosis

The availability of whole-genome sequencing (WGS) as a tool for the diagnosis and clinical management of tuberculosis (TB) offers considerable promise in the fight against this stubborn epidemic. However, like other new technologies, the best application of WGS remains to be determined, for both conceptual and technical reasons. In this review, we consider the potential value of WGS in the clinical laboratory for the detection of Mycobacterium tuberculosis and the prediction of antibiotic resistance. We also discuss issues pertaining to data generation, interpretation and dissemination, given that WGS has to date been generally performed in research labs where results are not necessarily packaged in a clinician-friendly format. Although WGS is far more accessible now than it was in the past, the transition from a research tool to study TB into a clinical test to manage this disease may require further fine-tuning. Improvements will likely come through iterative efforts that involve both the laboratories ready to move TB into the genomic era and the front-line clinical/public health staff who will be interpreting the results to inform management decisions.

Update on cutaneous tuberculosis

Tuberculosis continues to draw special attention from health care professionals and society in general. Cutaneous tuberculosis is an infection caused by M. tuberculosis complex, M. bovis and bacillus Calmette-Guérin. Depending on individual immunity, environmental factors and the type of inoculum, it may present varied clinical and evolutionary aspects. Patients with HIV and those using immunobiological drugs are more prone to infection, which is a great concern in centers where the disease is considered endemic. This paper aims to review the current situation of cutaneous tuberculosis in light of this new scenario, highlighting the emergence of new and more specific methods of diagnosis, and the molecular and cellular mechanisms that regulate the parasite-host interaction.

Totally drug-resistant tuberculosis and adjunct therapies

The first cases of totally drug-resistant (TDR) tuberculosis (TB) were reported in Italy 10 years ago; more recently, cases have also been reported in Iran, India and South Africa. Although there is no consensus on terminology, it is most commonly described as 'resistance to all first- and second-line drugs used to treat TB'. Mycobacterium tuberculosis (M.tb) acquires drug resistance mutations in a sequential fashion under suboptimal drug pressure due to monotherapy, inadequate dosing, treatment interruptions and drug interactions. The treatment of TDR-TB includes antibiotics with disputed or minimal effectiveness against M.tb, and the fatality rate is high. Comorbidities such as diabetes and infection with human immunodeficiency virus further impact on TB treatment options and survival rates. Several new drug candidates with novel modes of action are under late-stage clinical evaluation (e.g., delamanid, bedaquiline, SQ109 and sutezolid). 'Repurposed' antibiotics have also recently been included in the treatment of extensively drug resistant TB. However, because of mutations in M.tb, drugs will not provide a cure for TB in the long term. Adjunct TB therapies, including therapeutic vaccines, vitamin supplementation and/or repurposing of drugs targeting biologically and clinically relevant molecular pathways, may achieve better clinical outcomes in combination with standard chemotherapy. Here, we review broader perspectives of drug resistance in TB and potential adjunct treatment options.

Evaluation of the GenoType MTBDR assay for detection of rifampicin and isoniazid resistance in Mycobacterium tuberculosis complex isolates

Detection of drug resistance plays a critical role in tuberculosis treatment. The aim of this study was to evaluate the performance of GenoType Mycobacteria Drug Resistance (MTBDR) assay (Hain Lifescience, Germany) and to compare it with radiometric BACTEC 460 TB system (Becton Dickinson, USA) for the detection of rifampicin (RIF) and isoniazid (INH) resistance in 84 Mycobacterium tuberculosis complex (MTBC) isolates. RIF resistance was identified in 6 of 7 (85.7%) isolates and INH resistance was identified in 8 of 14 (57.1%) isolates by the GenoType MTBDR assay. Compared with BACTEC system, the sensitivity, specificity, positive predictive value and negative predictive values were 85.7%, 98.7%, 85.7% and 98.7% for RIF resistance; and 57.1%, 100%, 100% and 92.1% for INH resistance, respectively. GenoType MTBDR assay is reliable when tested specimen is resistant to the tested drugs. Although test was more successful in the detection of RIF resistance, it exhibited low sensitivity for the detection of INH resistance.

Bottlenecks and recommendations for the incorporation of new technologies in the tuberculosis laboratory network in Brazil

The World Health Organization (WHO) has recently recommended new technologies for the diagnosis of tuberculosis. The WHO recommendations include the development of a strategic plan for bringing the network up to grade; investment in supervision and quality control; and implementation of a system of laboratory environmental management. Without those measures having been taken, no new technology can be effectively incorporated. We surveyed the tuberculosis laboratory network in Brazil in order to identify possible bottlenecks for the incorporation of new technologies. We identified a lack of resources allocated to supervision and quality control; a low number of requests for cultures; a lack of effective laboratory information systems; and a lack of awareness regarding the future infrastructure needs of the laboratory network at the municipal level.

Identification of amino acids involved in catalytic process of M. tuberculosis GlmU acetyltransferase

M. tuberculosis GlmU is a bifunctional enzyme with acetyltransferase activity in C-terminus and uridyltransferase activity in N-terminus, and it is involved in the biosynthesis of glycosyl donor UDP-N-acetylglucosamine (UDP-GlcNAc). The crystal structure of M. tuberculosis GlmU clearly determines the active site and catalytic mechanism of GlmU uridyltransferase domain but not succeed in GlmU acetyltransferase domain. Sequence comparison analysis revealed highly conserved amino acid residues in the C-terminus between M. tuberculosis GlmU and GlmU enzymes from other bacteria. To find the essential amino acids related to M. tuberculosis GlmU acetyltransferase activity, we substituted 10 conserved amino acids in the acetyltransferase domain of M. tuberculosis GlmU by site-directed mutagenesis. All the mutant GlmU proteins were largely expressed in soluble and purified by affinity chromatography. Enzyme assays showed that K362A, H374A, Y398A and W460A mutants abolished more than 90% activity of M. tuberculosis GlmU acetyltransferase and totally lost the affinity with two substrates, suggesting the potential substrate-binding functions. However, K403A, S416A, N456A and E458A mutants exhibited decreased GlmU acetyltransferase activity and lower kinetic parameters, probably responsible for substrate releasing by conformation shifting.

Rise in rifampicin-monoresistant tuberculosis in Western Cape, South Africa

SETTING

Brewelskloof Hospital, Western Cape, South Africa.

OBJECTIVES

To verify the perceived increase in rifampicin monoresistant tuberculosis (RMR-TB) in the Cape Winelands-Overberg region and to identify potential risk factors.

DESIGN

A retrospective descriptive study of trends in RMR-TB over a 5-year period (2004-2008), followed by a case-control study of RMR and isoniazid (INH) monoresistant TB cases, diagnosed from April 2007 to March 2009, to assess for risk factors.

RESULTS

The total number of RMR-TB cases more than tripled, from 31 in 2004 to 98 in 2008. The calculated doubling time was 1.63 years (95%CI 1.18-2.66). For the assessment of risk factors, 95 RMR-TB cases were objectively verified on genotypic and phenotypic analysis. Of 108 specimens genotypically identified as RMR cases, 13 (12%) were misidentified, multidrug-resistant TB. On multivariate analysis, previous use of antiretroviral therapy (OR 6.4, 95%CI 1.3-31.8), alcohol use (OR 4.8, 95%CI 2.0-11.3) and age ≥ 40 years (OR 5.8, 95%CI 2.4-13.6) were significantly associated with RMR-TB.

CONCLUSION

RMR-TB is rapidly increasing in the study setting, particularly among patients with advanced human immunodeficiency virus (HIV) disease. Routine drug susceptibility testing should be considered in all TB-HIV co-infected patients, and absence of INH resistance should be confirmed phenotypically if genotypic RMR-TB is detected.

New and improved diagnostics for detection of drug-resistant pulmonary tuberculosis

PURPOSE OF REVIEW

Tuberculosis (TB) remains a global emergency and continues to kill 1.7 million people globally each year. Drug-resistant TB is now well established throughout the world and most TB patients are not being screened for drug resistance due to lack of laboratory resources and rapid accurate point-of-care tests. Accurate and rapid diagnosis of TB and drug-resistant TB is of paramount importance in establishing appropriate clinical management and infection control measures. During the past decade, there have been significant advances in diagnostic technologies for TB and drug-resistant TB. The purpose of this article is to review the current data, recommendations and evidence base for these tests.

RECENT FINDINGS

Second-line drug susceptibility testing (DST) is complex and expensive. Automated liquid culture systems and molecular line probe assays are recommended by the WHO as the current 'gold standard' for first-line DST. Liquid culture DST for aminoglycosides, polypeptides and fluoroquinolones has been shown to have relatively good reliability and reproducibility for diagnosis of extensively drug-resistant TB; however, DST for other second-line drugs (ethionamide, prothionamide, cycloserine, terizidone, para-aminosalicylic acid, clofazimine, amoxicillin-clavulanate, clarithromycin, linezolid) is not recommended. Automated liquid culture systems are currently recommended by the WHO as the 'gold standard' for second-line DST.

SUMMARY

In this review, we describe the phenotypic and genotypic methods currently available for the diagnosis of TB and drug-resistant forms of Mycobacterium tuberculosis and discuss future prospects for TB diagnostics. Current technologies for the detection of drug resistant M. tuberculosis vary greatly in terms of turnaround time, cost and complexity. Ultimately, the 'holy grail' diagnostic for TB must fulfil all technical specifications for a good point-of-care test, screen for drug resistance concurrently and be adaptable to the various health system levels and to countries with diverse economic status and TB burden.

Multiple introductions of multidrug-resistant tuberculosis into households, Lima, Peru

Two cases of multidrug-resistant tuberculosis (MDR TB) in a household are assumed to reflect within-household transmission. However, in high-incidence areas of MDR TB, secondary cases may arise through exposure to MDR TB in the community. To estimate the frequency of multiple introductions of MDR TB into households, we used spoligotyping and 24-loci mycobacterial interspersed repetitive unit- variable number tandem repeats to classify isolates from 101 households in Lima, Peru, in which >1 MDR TB patient received treatment during 1996-2004. We found different MDR TB strains in >10% of households. Alternate approaches for classifying matching strains produced estimates of multiple introductions in <38% of households. At least 4% of MDR TB patients were reinfected by a second strain of MDR Mycobacterium tuberculosis. These findings suggest that community exposure to MDR TB in Lima occurs frequently. Rapid drug sensitivity testing of strains from household contacts of known MDR TB patients is needed to identify optimal treatment regimens.

Kinetic properties of Mycobacterium tuberculosis bifunctional GlmU

The UDP-N-acetylglucosamine (UDP-GlcNAc) is present as one of the glycosyl donors for disaccharide linker (D-N-GlcNAc-L-rhamnose) and the precursor of peptidoglycan in mycobacteria. The bifunctional enzyme GlmU involves in the last two sequential steps of UDP-GlcNAc synthetic pathway. Glucosamine-1-phosphate acetyltransferase catalyzes the formation of N-acetylglucosamine-1-phosphate (GlcNAc-1-P) from glucosamine-1-phosphate (GlcN-1-P) and acetyl coenzyme A (Acetyl CoA), and N-acetylglucosamine-1-phosphate uridyltransferase catalyzes the synthesis of UDP-GlcNAc from GlcNAc-1-P and UTP. The previous studies demonstrating the essentiality of GlmU to mycobacterial survival supported GlmU as a novel and potential target for TB drugs. In this work, two accurate and simple colorimetric assays based on 96-well microtiter plate were developed to measure the kinetic properties of bifunctional GlmU including initial velocity, optimal temperature, optimal pH, the effect of Mg2+, and the kinetic parameters. Both of the colorimetric assays for bifunctional GlmU enzyme activities and the kinetic properties will facilitate high-throughput screening of GlmU inhibitors.

Experimental tuberculosis in the Wistar rat: a model for protective immunity and control of infection

Background

Despite the availability of many animal models for tuberculosis (TB) research, there still exists a need for better understanding of the quiescent stage of disease observed in many humans. Here, we explored the use of the Wistar rat model for the study of protective immunity and control of Mycobacterium tuberculosis (Mtb) infection.

Methodology/Principal Findings

The kinetics of bacillary growth, evaluated by the colony stimulating assay (CFU) and the extent of lung pathology in Mtb infected Wistar rats were dependent on the virulence of the strains and the size of the infecting inoculums. Bacillary growth control was associated with induction of T helper type 1 (Th1) activation, the magnitude of which was also Mtb strain and dose dependent. Histopathology analysis of the infected lungs demonstrated the formation of well organized granulomas comprising epithelioid cells, multinucleated giant cells and foamy macrophages surrounded by large numbers of lymphocytes. The late stage subclinical form of disease was reactivated by immunosuppression leading to increased lung CFU.

Conclusion

The Wistar rat is a valuable model for better understanding host-pathogen interactions that result in control of Mtb infection and potentially establishment of latent TB. These properties together with the ease of manipulation, relatively low cost and well established use of rats in toxicology and pharmacokinetic analyses make the rat a good animal model for TB drug discovery.

HIV-Associated Tuberculosis

The intersecting HIV and Tuberculosis epidemics in countries with a high disease burden of both infections pose many challenges and opportunities. For patients infected with HIV in high TB burden countries, the diagnosis of TB, ARV drug choices in treating HIV-TB coinfected patients, when to initiate ARV treatment in relation to TB treatment, managing immune reconstitution, minimising risk of getting infected with TB and/or managing recurrent TB, minimizing airborne transmission, and infection control are key issues. In addition, given the disproportionate burden of HIV in women in these settings, sexual reproductive health issues and particular high mortality rates associated with TB during pregnancy are important. The scaleup and resource allocation to access antiretroviral treatment in these high HIV and TB settings provide a unique opportunity to strengthen both services and impact positively in meeting Millennium Development Goal 6.

Evaluation of the MTBDRsl test for detection of second-line-drug resistance in Mycobacterium tuberculosis

The MTBDRsl assay (Hain Lifescience GmbH, Germany) is a new line probe assay for the detection of extensively drug-resistant tuberculosis (XDR TB). The test simultaneously detects resistance to ethambutol, aminoglycosides/cyclic peptides, and fluoroquinolones through detection of mutations in the relevant genes. The assay format is identical to the MTBDR Hain assay. The assay was evaluated for the detection of second-line-drug resistance in Vietnamese isolates using two sample sets from the microbiology department of Pham Ngoc Thach Hospital, Ho Chi Minh City, Viet Nam, with existing conventional phenotypic drug susceptibility results for second-line drugs: 41 consecutive fluoroquinolone-resistant isolates and 21 consecutive multidrug-resistant but fluoroquinolone-sensitive isolates. The sensitivity for detection of fluoroquinolone resistance was 75.6% (31/41) (95% confidence interval [95% CI], 59.7% to 87.6%), and for kanamycin resistance, the sensitivity was 100% (5/5) (95% CI, 47.8% to 100%). The sensitivity of the test for detection of ethambutol resistance was low, consistent with previous reports, at 64.2% (34/53) (95% CI, 49.8% to 76.9%). The specificity of the test was 100% for all three drugs. These data suggest that the MTBDRsl assay is a rapid, specific test for the detection of XDR TB but should not be used exclusively to "rule out" second-line-drug resistance. Further operational evaluation is required and should be integrated with evaluations of the MTBDR test.

Evaluation of the analytical performance of the Xpert MTB/RIF assay

We performed the first studies of analytic sensitivity, analytic specificity, and dynamic range for the new Xpert MTB/RIF assay, a nucleic acid amplification-based diagnostic system that detects Mycobacterium tuberculosis and rifampin (RIF) resistance in under 2 h. The sensitivity of the assay was tested with 79 phylogenetically and geographically diverse M. tuberculosis isolates, including 42 drug-susceptible isolates and 37 RIF-resistant isolates containing 13 different rpoB mutations or mutation combinations. The specificity of the assay was tested with 89 nontuberculosis bacteria, fungi, and viruses. The Xpert MTB/RIF assay correctly identified all 79 M. tuberculosis isolates and correctly excluded all 89 nontuberculosis isolates. RIF resistance was correctly identified in all 37 resistant isolates and in none of the 42 susceptible isolates. Dynamic range was assessed by adding 10(2) to 10(7) CFU of M. tuberculosis into M. tuberculosis-negative sputum samples. The assay showed a log-linear relationship between cycle threshold and input CFU over the entire concentration range. Resistance detection in the presence of different mixtures of RIF-resistant and RIF-susceptible DNA was assessed. Resistance detection was dependent on the particular mutation and required between 65% and 100% mutant DNA to be present in the sample for 95% certainty of resistance detection. Finally, we studied whether assay specificity could be affected by cross-contaminating amplicons generated by the GenoType MTBDRplus assay. M. tuberculosis was not detected until at least 10(8) copies of an MTBDRplus amplicon were spiked into 1 ml of sputum, suggesting that false-positive results would be unlikely to occur.

Early treatment outcomes and HIV status of patients with extensively drug-resistant tuberculosis in South Africa: a retrospective cohort study

BACKGROUND

Data from Kwazulu Natal, South Africa, suggest that almost all patients with extensively drug-resistant (XDR) tuberculosis are HIV-positive, with a fatal outcome. Since, there are few data for the treatment-related outcomes of XDR tuberculosis in settings with a high HIV prevalence, we investigated the associations of these diseases in such settings to formulate recommendations for control programmes.

METHODS

In a retrospective cohort study, we analysed the case records of patients (>16 years old) with XDR tuberculosis (culture-proven at diagnosis) between August, 2002, and February, 2008, at four designated provincial treatment facilities in South Africa. We used Cox proportional hazards regression models to assess risk factors associated with the outcomes-mortality and culture conversion.

FINDINGS

195 of 227 patients were analysed. 21 died before initiation of any treatment, and 174 patients (82 with HIV infection) were treated. 62 (36%) of these patients died during follow-up. The number of deaths was not significantly different in patients with or without HIV infection: 34 (41%) of 82 versus 28 (30%) of 92 (p=0.13). Treatment with moxifloxacin (hazard ratio 0.11, 95% CI 0.01-0.82; p=0.03), previous culture-proven multidrug-resistant tuberculosis (5.21, 1.93-14.1; p=0.001), and number of drugs used in a regimen (0.59, 0.45-0.78, p<0.0001) were independent predictors of death. Fewer deaths occurred in patients with HIV infection given highly active antiretroviral therapy than in those who were not (0.38, 0.18-0.80; p=0.01). 33 (19%) of 174 patients showed culture conversion, of which 23 (70%) converted within 6 months of initiation of treatment.

INTERPRETATION

In South Africa, patients with XDR tuberculosis, a substantial proportion of whom are not infected with HIV, have poor management outcomes. Nevertheless, survival in patients with HIV infection is better than previously reported. The priorities for the country are still prevention of XDR tuberculosis, and early detection and management of multidrug-resistant and XDR tuberculosis through strengthened programmes and laboratory capacity.

FUNDING

South African Medical Research Council, European Union Framework 7 program, and European Developing Countries Clinical Trials Partnership.

Molecular detection of rifampin and isoniazid resistance to guide chronic TB patient management in Burkina Faso

Background

Drug-resistant tuberculosis (DR-TB) is considered a real threat to the achievement of TB control. Testing of mycobacterial culture and testing of drug susceptibility (DST) capacity are limited in resource-poor countries, therefore inadequate treatment may occur, favouring resistance development. We evaluated the molecular assay GenoType^® MTBDRplus (Hain Lifescience, Germany) in order to detect DR-TB directly in clinical specimens as a means of providing a more accurate management of chronic TB patients in Burkina Faso, a country with a high TB-HIV co-infection prevalence.

Methods

Samples were collected in Burkina Faso where culture and DST are not currently available, and where chronic cases are therefore classified and treated based on clinical evaluation and sputum-smear microscopy results. One hundred and eight chronic TB patients (sputum smear-positive, after completing a re-treatment regimen for pulmonary TB under directly observed therapy) were enrolled in the study from December 2006 to October 2008. Two early morning sputum samples were collected from each patient, immediately frozen, and shipped to Italy in dry ice. Samples were decontaminated, processed for smear microscopy and DNA extraction. Culture was attempted on MGIT960 (Becton Dickinson, Cockeysville, USA) and decontaminated specimens were analyzed for the presence of mutations conferring resistance to rifampin and isoniazid by the molecular assay GenoType^® MTBDRplus.

Results

We obtained a valid molecular test result in 60/61 smear-positive and 47/47 smear-negative patients.

Among 108 chronic TB cases we identified patients who (i) harboured rifampin- and isoniazid-susceptible strains (n 24), (ii) were negative for MTB complex DNA (n 24), and (iii) had non-tuberculous mycobacteria infections (n 13). The most represented mutation conferring rifampin-resistance was the D516V substitution in the hotspot region of the rpoB gene (43.8% of cases). Other mutations recognized were the H526D (15.6%), the H526Y (15.6%), and the S531L (9.4%).

All isoniazid-resistant cases (n 36) identified by the molecular assay were carrying a S315T substitution in the katG gene. In 41.7% of cases, a mutation affecting the promoter region of the inhA gene was also detected.

Conclusion

The GenoType^® MTBDRplus assay performed directly on sputum specimens improves the management of chronic TB cases allowing more appropriate anti-TB regimens.