Isoniazid Monoresistance: A Precursor to Multidrug-Resistant Tuberculosis?

Multidrug-resistant tuberculosis

Tuberculosis (TB) remains the foremost cause of death by an infectious disease globally. Multidrug-resistant or rifampicin-resistant TB (MDR/RR-TB; resistance to rifampicin and isoniazid, or rifampicin alone) is a burgeoning public health challenge in several parts of the world, and especially Eastern Europe, Russia, Asia and sub-Saharan Africa. Pre-extensively drug-resistant TB (pre-XDR-TB) refers to MDR/RR-TB that is also resistant to a fluoroquinolone, and extensively drug-resistant TB (XDR-TB) isolates are additionally resistant to other key drugs such as bedaquiline and/or linezolid. Collectively, these subgroups are referred to as drug-resistant TB (DR-TB). All forms of DR-TB can be as transmissible as rifampicin-susceptible TB; however, it is more difficult to diagnose, is associated with higher mortality and morbidity, and higher rates of post-TB lung damage. The various forms of DR-TB often consume >50% of national TB budgets despite comprising <5-10% of the total TB case-load. The past decade has seen a dramatic change in the DR-TB treatment landscape with the introduction of new diagnostics and therapeutic agents. However, there is limited guidance on understanding and managing various aspects of this complex entity, including the pathogenesis, transmission, diagnosis, management and prevention of MDR-TB and XDR-TB, especially at the primary care physician level.

Spatial pattern of isoniazid-resistant tuberculosis and its associated factors among a population with migrants in China: a retrospective population-based study

Background

Isoniazid-resistant, rifampicin-susceptible tuberculosis (Hr-TB) globally exhibits a high prevalence and serves as a potential precursor to multidrug-resistant tuberculosis (MDR-TB). Recognizing the spatial distribution of Hr-TB and identifying associated factors can provide strategic entry points for interventions aimed at early detection of Hr-TB and prevention of its progression to MDR-TB. This study aims to analyze spatial patterns and identify socioeconomic, demographic, and healthcare factors associated with Hr-TB in Shanghai at the county level.

Method

We conducted a retrospective study utilizing data from TB patients with available Drug Susceptible Test (DST) results in Shanghai from 2010 to 2016. Spatial autocorrelation was explored using Global Moran's I and Getis-Ord G i ∗ statistics. A Bayesian hierarchical model with spatial effects was developed using the INLA package in R software to identify potential factors associated with Hr-TB at the county level.

Results

A total of 8,865 TB patients with DST were included in this analysis. Among 758 Hr-TB patients, 622 (82.06%) were new cases without any previous treatment history. The drug-resistant rate of Hr-TB among new TB cases in Shanghai stood at 7.20% (622/8014), while for previously treated cases, the rate was 15.98% (136/851). Hotspot areas of Hr-TB were predominantly situated in southwestern Shanghai. Factors positively associated with Hr-TB included the percentage of older adult individuals (RR = 3.93, 95% Crl:1.93-8.03), the percentage of internal migrants (RR = 1.35, 95% Crl:1.15-1.35), and the number of healthcare institutions per 100 population (RR = 1.17, 95% Crl:1.02-1.34).

Conclusion

We observed a spatial heterogeneity of Hr-TB in Shanghai, with hotspots in the Songjiang and Minhang districts. Based on the results of the models, the internal migrant population and older adult individuals in Shanghai may be contributing factors to the emergence of areas with high Hr-TB notification rates. Given these insights, we advocate for targeted interventions, especially in identified high-risk hotspots and high-risk areas.

Analysis of drug resistance among difficult-to-treat tuberculosis patients in Ghana identifies several pre-XDR TB cases

Background

Resistance to tuberculosis (TB) drugs has become a major threat to global control efforts. Early case detection and drug susceptibility profiling of the infecting bacteria are essential for appropriate case management. The objective of this study was to determine the drug susceptibility profiles of difficult-to-treat (DTT) TB patients in Ghana.

Methods

Sputum samples obtained from DTT-TB cases from health facilities across Ghana were processed for rapid diagnosis and detection of drug resistance using the Genotype MTBDRplus and Genotype MTBDRsl.v2 from Hain Life science.

Results

A total of 298 (90%) out of 331 sputum samples processed gave interpretable bands out of which 175 (58.7%) were resistant to at least one drug (ANYr); 16.8% (50/298) were isoniazid-mono-resistant (INHr), 16.8% (50/298) were rifampicin-mono-resistant (RIFr), and 25.2% (75/298) were MDR. 24 (13.7%) of the ANYr were additionally resistant to at least one second line drug: 7.4% (2 RIFr, 1 INHr, and 10 MDR samples) resistant to only FQs and 2.3% (2 RIFr, 1 INHr, and 1 MDR samples) resistant to AMG drugs kanamycin (KAN), amikacin (AMK), capreomycin (CAP), and viomycin (VIO). Additionally, there were 4.0% (5 RIFr and 2 MDR samples) resistant to both FQs and AMGs. 81 (65.6%) out of 125 INH-resistant samples including INHr and MDR had katG-mutations (MT) whereas 15 (12%) had inhApro-MT. The remaining 28 (22.4%) had both katG and inhA MT. All the 19 FQ-resistant samples were gyrA mutants whereas the 10 AMGs were rrs (3), eis (3) as well as rrs, and eis co-mutants (4). Except for the seven pre-XDR samples, no sample had eis MT.

Conclusion

The detection of several pre-XDR TB cases in Ghana calls for intensified drug resistance surveillance and monitoring of TB patients to, respectively, ensure early diagnosis and treatment compliance.

Highly Sensitive Detection of Isoniazid Heteroresistance in Mycobacterium Tuberculosis by Droplet Digital PCR

Purpose

The drug resistance of Mycobacterium tuberculosis constitutes a major public health threat. Existing approaches make it challenging to detect low levels of drug-resistant TB, also known as heteroresistance (HR), in a population. The recently found droplet digital PCR (ddPCR) is a sensitive method for determining the precise amount of nucleic acid in a sample. We used ddPCR to test the Mycobacterium tuberculosis heteroresistance because it delivers more exact quantitative data without the need for a reference curve.

Patients and Methods

A TaqMan-MGB probe mutation detection assay was developed in order to determine the mutant and wild-type sequences of the isoniazid resistance katG (315) gene. We produced heteroresistant MTB combinations, which were subsequently identified by ddPCR, qPCR, and MeltPro/INH. In addition, 21 clinical sputum samples with positive smears were used to validate each method’s capacity to determine HR in sputum.

Results

We discovered that ddPCR can detect mutant sequences in as few as 0.01% of a combination. DeepMelt TB/INH, which is less sensitive in comparison, cannot detect HR with high resolution and requires a mutation rate of 50% to identify. qPCR likewise has a high resolution of 0.02%, but unlike ddPCR, it cannot determine the exact number of mutations. Our assay is applicable to sputum as well. ddPCR found a katG 315 substitution in two sputums with extremely low values of HR (0.26% and 0.14%). In 21 samples of clinical sputum, the HR prevalence of INH was 9.5%.

Conclusion

This work demonstrates that a well-designed ddPCR HR detection test can detect low levels of HR with high accuracy and consistency and gives new information for the clinical diagnosis of drug resistance.

Mycobacterium tuberculosis Drug Resistance in Ethiopia: An Updated Systematic Review and Meta-Analysis

Background: Tuberculosis (TB) remains a significant global public health issue, despite advances in diagnostic technologies, substantial global efforts, and the availability of effective chemotherapies. Mycobacterium tuberculosis, a species of pathogenic bacteria resistant to currently available anti-TB drugs, is on the rise, threatening national and international TB-control efforts. This systematic review and meta-analysis aims to estimate the pooled prevalence of drug-resistant TB (DR-TB) in Ethiopia. Materialsand Methods: A systematic literature search was undertaken using PubMed/MEDLINE, HINARI, the Web of Science, ScienceDirect electronic databases, and Google Scholar (1 January 2011 to 30 November 2020). After cleaning and sorting the records, the data were analyzed using STATA 11. The study outcomes revealed the weighted pooled prevalence of any anti-tuberculosis drug resistance, any isoniazid (INH) and rifampicin (RIF) resistance, monoresistance to INH and RIF, and multidrug-resistant TB (MDR-TB) in newly diagnosed and previously treated patients with TB. Results: A total of 24 studies with 18,908 patients with TB were included in the final analysis. The weighted pooled prevalence of any anti-TB drug resistance was 14.25% (95% confidence interval (CI): 7.05–21.44%)), whereas the pooled prevalence of any INH and RIF resistance was found in 15.62% (95%CI: 6.77–24.47%) and 9.75% (95%CI: 4.69–14.82%) of patients with TB, respectively. The pooled prevalence for INH and RIF-monoresistance was 6.23% (95%CI: 4.44–8.02%) and 2.33% (95%CI: 1.00–3.66%), respectively. MDR-TB was detected in 2.64% (95%CI: 1.46–3.82%) of newly diagnosed cases and 11.54% (95%CI: 2.12–20.96%) of retreated patients with TB, while the overall pooled prevalence of MDR-TB was 10.78% (95%CI: 4.74–16.83%). Conclusions: In Ethiopia, anti-tuberculosis drug resistance is widespread. The estimated pooled prevalence of INH and RIF-monoresistance rates were significantly higher in this review than in previous reports. Moreover, MDR-TB in newly diagnosed cases remained strong. Thus, early detection of TB cases, drug-resistance testing, proper and timely treatment, and diligent follow-up of TB patients all contribute to the improvement of DR-TB management and prevention. Besides this, we urge that a robust, routine laboratory-based drug-resistance surveillance system be implemented in the country.

A retrospective Cohort Study on the Treatment Outcomes and Genotyping of Isoniazid-Resistant Tuberculosis Patients in Eastern China

OBJECTIVES

Isoniazid resistance might be overlooked due to the priority of detection of rifampicin-resistant tuberculosis. It was urgent to reveal the current situation of isoniazid-resistant tuberculosis (HR-TB), including unfavorable outcomes and bacterial factors.

METHODS

A retrospective cohort study was undertaken by enrolling 120 HR-TB and 193 drug-sensitive tuberculosis (DS-TB). 24 loci MIRU-VNTR and Spoligotyping were adopted for genotyping.

RESULTS

We found 106 (88.3%) HR-TB and 165(85.5%) DS-TB were treated with the first-line drugs. Meanwhile, 12 (10.0%) patients of the HR-TB and 7 (3.63%) patients of the DS-TB involved adverse treatment outcomes, respectively. (χ² =5.271, P=0.028). A total of 78 DNAs from HR Mycobacterium tuberculosis and 114 DNAs from DS Mycobacterium tuberculosis were available for MIRU-VNTR and Spoligotyping. The clustering rate was 17.9% (14/78) for HR-TB and 16.7% (19/114) for DS-TB, and reached no significant difference (χ² =0.05, P=0.8171). The Beijing family strains accounted for 83.7% (65/78) among HR-TB, 80.0% (91/114) among DS-TB (χ²=0.37, P=0.5407). The adverse treatment outcomes for HR-TB all occurred in patients infected with Beijing family strains (13.8%), but no difference was found between Beijing and non-Beijing genotypes (P=0.342).

CONCLUSION

the adverse outcome of HR-TB was significantly higher than that of DS-TB, and most of the HR-TB patients were receiving a standard first-line regimen. Although the clustering rate and Beijing genotype distribution among HR-TB and DS-TB showed no significant difference, Beijing genotype was the dominant genotype and the proportion of Beijing genotype was only slightly high among HR-TB than DS-TB.

Spoligotype-based population structure and isoniazid-resistance gene mutation of Mycobacterium tuberculosis isolates from Thailand

OBJECTIVES

The present study aims to investigate the population structure of Thai Mycobacterium tuberculosis (MTB) isolates, the anti-tuberculosis (TB) drug resistance and to determine the most frequent genetic mutations conferring the isoniazid (INH) resistance.

METHODS

Genomic DNA from 287 MTB clinical isolates were extracted and used for: spoligotyping, amplification and sequencing analysis of region of different (RD) 105, and the INH-resistance (IR) associated genes, inhA, katG and oxyR-ahpC.

RESULTS

Eighty-one clinical isolates were resistant to at least one first-line drug, 53 of these were resistant to INH. All strains were classified into three lineages based on their spoligotypes: East-Asia (EA)/Beijing, Indo-Oceanic (IO) and Euro-American (EuA). EA and IO lineages revealed a strong association with anti-TB drug resistance (p=0.005 and 0.013, respectively). A total of 33 mutations were found among IR isolates, which for 28 (84.8%), 3 (9.1%) and 2 (6.1%) occurred in katG, inhA, and oxyR-ahpC genes, respectively. Moreover, the most commom mutations found were 54.7% of IR presented Ser315Thr at katG (54.7%) and C-15T at inhA (15.1%) presented. This result suggests the involvement of other genetic markers or other mechanisms of resistance.

CONCLUSION

This study provides information about strains diversity, drug resistance profiles and their possible association. EA and IO lineages were predominant in Thailand, and they were highly associated with anti-TB drug resistance. Testing two mutation including katGSer315Thr and inhA-15C→T could detect 68% of the IR strains.

Isoniazid resistance in patients with Extrapulmonary Tuberculosis using line probe assay in a private multispecialty hospital in Bangalore, India

We aimed to study the rate of isoniazid (INH) resistance in Extrapulmonary Tuberculosis samples from a private care setting. A Line probe assay was performed on 74 culture isolates of Mycobacterium tuberculosis or directly on extrapulmonary samples received in our laboratory from 2018 to 2021. The INH mono-resistance among these extrapulmonary samples was 6.7%. (5 among 74) (95% CI: 1.04%-12.48%) Resistance to rifampicin was not detected. Increasing the availability and leveraging public private partnerships in hospitals for universal testing for INH resistance may increase detection of INH monoresistance in EP-TB and improve the strategy for TB elimination.

Rapid and Simple Detection of Isoniazid-Resistant Mycobacterium tuberculosis Utilizing a DNA Chromatography-Based Technique

Despite the availability of anti-tuberculosis drugs, the treatment of tuberculosis has been complicated by drug-resistant tuberculosis. The early detection of drug resistance makes early treatment possible. However, the available tools are mainly for rifampicin resistance detection, and the existing isoniazid resistance detection method is expensive, highly technical, and complicated, making it unsustainable for use in developing nations. This study aimed to develop a simple, rapid, and low-cost diagnostic kit for isoniazid-resistant tuberculosis using the single-stranded tag hybridization method to target an isoniazid resistance-conferring mutation. Specificity and sensitivity were assessed using DNA extracted from 49 isoniazid-resistant and 41 isoniazid-susceptible Mycobacterium tuberculosis clinical isolates cultured in mycobacterial growth indicator tubes. Positive signals were observed on mutant and wild-type lines with 100% sensitivity and specificity compared with Sanger sequencing results. In contrast, no positive signal was observed for non-tuberculosis mycobacteria. The detection limit of this method was 10³ CFU or less. The STH-PAS system for isoniazid-resistant M. tuberculosis detection developed in this study offers a better alternative to conventional phenotypic isoniazid resistance determination, which will be of both clinical and epidemiological significance in resource-limited nations.

Assessing whether isoniazid is essential during the first 14 days of tuberculosis therapy: a phase 2a, open-label, randomised controlled trial

Background

Clinical studies suggest that isoniazid contributes rapid bacterial killing during the initial two days of tuberculosis treatment but that isoniazid's activity declines significantly after day three. We conducted a 14-day phase IIa open label, randomized trial to assess the essentiality of isoniazid in standard tuberculosis therapy.

Methods

A total of 69 adults with newly diagnosed sputum-positive tuberculosis from the South African Western Cape region were enrolled and randomized to a four-arm parallel assignment model. Participants were followed for 14 days as inpatients at either the University of Cape Town Lung Institute or at the TASK Applied Science clinical research organization. All arms received standard daily rifampicin, ethambutol, and pyrazinamide but differed as follows: isoniazid only on days one and two (n=17), isoniazid on days one and two then moxifloxacin on days three through 14 (n=16), no isoniazid (n=18), and a control group that received isoniazid for all 14 days (standard therapy, n=18). The primary endpoint was the rate of colony forming unit (CFU) decline during the first 14 days of treatment.

Results

For 62 participants analyzed, the initial 14-day mean daily fall in log₁₀ CFU (95% CI) was 0·14 (0·11, 0·18) for participants receiving isoniazid for two days only; 0·13 (0·09, 0·17) for participants receiving isoniazid for two days followed by moxifloxacin; 0·12 (0·08, 0·15) for those not receiving isoniazid; and 0·13 (0·09, 0·16) for the standard therapy group.

Conclusions

The 14 day EBA for the combination rifampicin, ethambutol, and pyrazinamide was not significantly changed by the addition of isoniazid for the first two days or for the first 14 days of treatment. In a post hoc analysis, significantly higher day-two EBAs were observed for all groups among participants with higher baseline sputum CFUs. Our finding that INH does not contribute to EBA suggests that INH could be replaced with another drug during standard treatment to improve efficacy and decrease rates of resistance to first-line drugs. (Funded by the NIH AIDS Clinical Trial Groups and NIH; A5307 ClinicalTrials.gov number, NCT01589497).

Incidence, treatment, and outcomes of isoniazid mono-resistant Mycobacterium tuberculosis infections in Alberta, Canada from 2007-2017

Isoniazid resistant Mycobacterium tuberculosis (Hr-TB) is the most frequently encountered TB resistance phenotype in North America but limited data exist on the effectiveness of current therapeutic regimens. Ineffective treatment of Hr-TB increases patient relapse and anti-mycobacterial resistance, specifically MDR-TB. We undertook a multi-centre, retrospective review of culture-positive Hr-TB patients in Alberta, Canada (2007-2017). We assessed incidence and treatment outcomes, with a focus on fluoroquinolone (FQ)-containing regimens, to understand the risk of unsuccessful outcomes. Rates of Hr-TB were determined using the mid-year provincial population and odds of unsuccessful treatment was calculated using a Fisher's Exact test. One hundred eight patients of median age 37 years (IQR: 26-50) were identified with Hr-TB (6.3%), 98 of whom were able to be analyzed. Seven percent reported prior treatment. Rate of foreign birth was high (95%), but continent of origin did not predict Hr-TB (p = 0.47). Mean compliance was 95% with no difference between FQ and non-FQ regimens (p = 1.00). Treatment success was high (91.8%). FQ-containing regimens were frequently initiated (70%), with no difference in unsuccessful outcomes compared to non-FQ-containing regimens (5.8% vs. 13.8%, OR 0.4, 95% CI 0.1-2.3, p = 0.23). Only one patient (1%) utilizing a less common non-FQ-based regimen including two months of pyrazinamide developed secondary multidrug resistance. Unsuccessful treatment was low (<10%) relative to comparable literature (~15%) and showed similar outcomes for FQ and non-FQ-based regimens and no deficit to those using intermittent fluoroquinolones in the continuation phase of treatment. Our findings are similar to recent data, however prospective, randomized trials of adequate power are needed to determine the optimal treatment for Hr-TB.

Detection of Second Line Drug Resistance among Drug Resistant Mycobacterium Tuberculosis Isolates in Botswana

The emergence and transmission of multidrug resistant (MDR) and extensively drug resistant (XDR) Mycobacterium tuberculosis (M.tb) strains is a threat to global tuberculosis (TB) control. The early detection of drug resistance is critical for patient management. The aim of this study was to determine the proportion of isolates with additional second-line resistance among rifampicin and isoniazid resistant and MDR-TB isolates. A total of 66 M.tb isolates received at the National Tuberculosis Reference Laboratory between March 2012 and October 2013 with resistance to isoniazid, rifampicin or both were analyzed in this study. The genotypes of the M.tb isolates were determined by spoligotyping and second-line drug susceptibility testing was done using the Hain Genotype MTBDRsl line probe assay version 2.0. The treatment outcomes were defined according to the Botswana national and World Health Organization (WHO) guidelines. Of the 57 isolates analyzed, 33 (58%) were MDR-TB, 4 (7%) were additionally resistant to flouroquinolones and 3 (5%) were resistant to both fluoroquinolones and second-line injectable drugs. The most common fluoroquinolone resistance-conferring mutation detected was gyrA A90V. All XDR-TB cases remained smear or culture positive throughout the treatment. Our study findings indicate the importance of monitoring drug resistant TB cases to ensure rapid detection of second-line drug resistance.