Emergence Of Drug-resistant Tuberculosis Research Articles

Transmission characteristics in Tuberculosis by WGS: nationwide cross-sectional surveillance in China

China, with the third largest share of global tuberculosis cases, faces a substantial challenge in its healthcare system as a result of the high burden of multidrug-resistant and rifampicin-resistant tuberculosis (MDR/RR-TB). This study employs a genomic epidemiological approach to assess recent tuberculosis transmissions between individuals, identifying potential risk factors and discerning the role of transmitted resistant isolates in the emergence of drug-resistant tuberculosis in China. We conducted a population-based retrospective study on 5052 Mycobacterium tuberculosis (MTB) isolates from 70 surveillance sites using whole genome sequencing (WGS). Minimum spanning tree analysis identified resistance mutations, while epidemiological data analysis pinpointed transmission risk factors. Of the 5052 isolates, 23% (1160) formed 452 genomic clusters, with 85.6% (387) of the transmissions occurring within the same counties. Individuals with younger age, larger family size, new cases, smear positive, and MDR/RR were at higher odds for recent transmission, while higher education (university and above) and occupation as a non-physical workers emerged as protective factors. At least 61.4% (251/409) of MDR/RR-TB were likely a result of recent transmission of MDR/RR isolates, with previous treatment (crude OR = 2.77), smear-positive (cOR = 2.07) and larger family population (cOR = 1.13) established as risk factors. Our findings highlight that local transmission remains the predominant form of TB transmission in China. Correspondingly, drug-resistant tuberculosis is primarily driven by the transmission of resistant tuberculosis isolates. Targeted interventions for high-risk populations to interrupt transmission within the country will likely provide an opportunity to reduce the prevalence of both tuberculosis and drug-resistant tuberculosis.

The clinical profile and outcomes of drug resistant tuberculosis in Central Province of Zambia

BackgroundThe emergence of Drug Resistant Tuberculosis (DR-TB) is one of the main public health and economic problems facing the world today. DR-TB affects mostly those in economically productive years and prevents them from being part of the workforce needed for economic growth. The aim of this study was to determine the Clinical Profile and Outcomes of DR-TB in Central Province of Zambia.MethodsThis was a retrospective cross sectional study that involved a review of records of patients with confirmed DR-TB who were managed at Kabwe Central Hospital’s Multi-Drug Resistant TB (MDR-TB) Ward from the year 2017 to 2021. 183 patients were managed during this period and all were recruited in the study. Data was collected from DR-TB registers and patient files and then entered in SPSS version 22 where all statistical analyses were performed.ResultsThe study revealed that the prevalence of DR-TB among registered TB patients in Central Province was 1.4%. Majority of those affected were adults between the ages of 26 and 45 years (63.9%). The study also found that more than half of the patients were from Kabwe District (60.7%). Other districts with significant number of cases included Kapiri Mposhi 19 (10.4%), Chibombo 12 (6.6%), Chisamba 10 (5.5%), Mumbwa 7 (3.8%) and Mkushi 7 (3.8%). Furthermore, the analysis established that most of the patients had RR-TB (89.6%). 9.3% had MDR-TB, 0.5% had IR-TB and 0.5% had XDR-TB. RR-TB was present in 93.8% of new cases and 88.9% of relapse cases. MDR-TB was present in 6.2% of new cases and 10% of relapse cases. With regard to outcomes of DR-TB, the investigation revealed that 16.9% of the patients had been declared cured, 45.9% had completed treatment, 6% were lost to follow up and 21.3% had died. Risk factors for mortality on multivariate analysis included age 36–45 years (adjusted odds ratio [aOR] 0.253, 95% CI [0.70–0.908] p = 0.035) and male gender (aOR 0.261, 95% CI [0.107–0.638] p = 0.003).ConclusionThe research has shown beyond doubt that the burden of DR-TB in Central Province is high. The study recommends putting measures in place that will help improve surveillance, early detection, early initiation of treatment and proper follow up of patients.

Indole Propionic Acid Disturbs the Normal Function of Tryptophanyl-tRNA Synthetase in Mycobacterium tuberculosis.

Tuberculosis (TB) is the leading infectious disease caused by Mycobacterium tuberculosis and the second-most contagious killer after COVID-19. The emergence of drug-resistant TB has caused a great need to identify and develop new anti-TB drugs with novel targets. Indole propionic acid (IPA), a structural analog of tryptophan (Trp), is active against M. tuberculosis in vitro and in vivo. It has been verified that IPA exerts its antimicrobial effect by mimicking Trp as an allosteric inhibitor of TrpE, which is the first enzyme in the Trp synthesis pathway of M. tuberculosis. However, other Trp structural analogs, such as indolmycin, also target tryptophanyl-tRNA synthetase (TrpRS), which has two functions in bacteria: synthesis of tryptophanyl-AMP by catalyzing ATP + Trp and producing Trp-tRNATrp by transferring Trp to tRNATrp. So, we speculate that IPA may also target TrpRS. In this study, we found that IPA can dock into the Trp binding pocket of M. tuberculosis TrpRS (TrpRSMtb), which was further confirmed by isothermal titration calorimetry (ITC) assay. The biochemical analysis proved that TrpRS can catalyze the reaction between IPA and ATP to generate pyrophosphate (PPi) without Trp as a substrate. Overexpression of wild-type trpS in M. tuberculosis increased the MIC of IPA to 32-fold, and knock-down trpS in Mycolicibacterium smegmatis made it more sensitive to IPA. The supplementation of Trp in the medium abrogated the inhibition of M. tuberculosis by IPA. We demonstrated that IPA can interfere with the function of TrpRS by mimicking Trp, thereby impeding protein synthesis and exerting its anti-TB effect.

The structure of Mycobacterium thermoresistibile MmpS5 reveals a conserved disulfide bond across mycobacteria.

The tuberculosis (TB) emergency has been a pressing health threat for decades. With the emergence of drug-resistant TB and complications from the COVID-19 pandemic, the TB health crisis is more serious than ever. Mycobacterium tuberculosis (Mtb), the causative agent of TB, requires iron for its survival. Thus, Mtb has evolved several mechanisms to acquire iron from the host. Mtb produces two siderophores, mycobactin and carboxymycobactin, which scavenge for host iron. Mtb siderophore-dependent iron acquisition requires the export of apo-siderophores from the cytosol to the host environment and import of iron-bound siderophores. The export of Mtb apo-siderophores across the inner membrane is facilitated by two mycobacterial inner membrane proteins with their cognate periplasmic accessory proteins, designated MmpL4/MmpS4 and MmpL5/MmpS5. Notably, the Mtb MmpL4/MmpS4 and MmpL5/MmpS5 complexes have also been implicated in the efflux of anti-TB drugs. Herein, we solved the crystal structure of M. thermoresistibile MmpS5. The MmpS5 structure reveals a previously uncharacterized, biologically relevant disulfide bond that appears to be conserved across the Mycobacterium MmpS4/S5 homologs, and comparison with structural homologs suggests that MmpS5 may be dimeric.

Healthcare seeking behavior and delays in case of Drug-Resistant Tuberculosis patients in Bangladesh: Findings from a cross-sectional survey.

The emergence of Drug-Resistant Tuberculosis (DR-TB) has become a major threat globally and Bangladesh is no exception. Delays in healthcare seeking, proper diagnosis and initiation of treatment cause continuous transmission of the resistant tubercule bacilli through the communities. This study aimed to assess the different health care-seeking behaviors and delays among DR-TB patients in Bangladesh. A prospective cross-sectional study was conducted from November to December 2018, among 92 culture positive and registered DR-TB patients in four selected hospitals in Bangladesh. Data were collected through face-to-face interviews with survey questionnaire as well as record reviews. Among the 92 study participants, the median patient delay was 7 (IQR 3, 15) days, the median diagnostic delay was 88 (IQR 36.5, 210), the median treatment delay was 7 (IQR 4,12) days, and the median total delay among DR-TB patients was 108.5 (IQR 57.5, 238) days. 81.32% sought initial care from informal healthcare providers. The majority (68.48%) of the informal healthcare providers were drug sellers while 60.87% of patients sought care from more than four healthcare points before being diagnosed with DR-TB. The initial care seeking from multiple providers was associated with diagnostic and total delays. In Bangladesh, DR-TB cases usually seek care from multiple providers, particularly from informal providers, and among them, alarmingly higher healthcare-seeking related delays were noted. Immediate measures should be taken both at the health system levels and, in the community, to curb transmission and reduce the burden of the disease.

Genotypic and phenotypic drug resistance patterns of Mycobacterium tuberculosis isolated from presumptive pulmonary tuberculosis patients in Ethiopia: A multicenter study.

The emergence of drug-resistant tuberculosis (DR-TB) has been a major obstacle to global tuberculosis control programs, especially in developing countries, including Ethiopia. This study investigated drug resistance patterns and associated mutations of Mycobacterium tuberculosis Complex (MTBC) isolates from the Amhara, Gambella, and Benishangul-Gumuz regions of Ethiopia. A cross-sectional study was conducted using 128 MTBC isolates obtained from patients with presumptive tuberculosis (TB). Phenotypic (BACTEC MGIT 960) and genotypic (MTBDRplus and MTBDRsl assays) methods were used for drug susceptibility testing. Data were entered into Epi-info and analyzed using SPSS version 25. Frequencies and proportions were determined to describe drug resistance levels and associated mutations. Of the 127 isolates recovered, 100 (78.7%) were susceptible to four first-line anti-TB drugs. Any drug resistance, polydrug resistance, and multi-drug resistance (MDR) were detected in 21.3% (27), 15.7% (20), and 15% (19) of the isolates, respectively, by phenotypic and/or genotypic methods. Mono-resistance was observed for Isoniazid (INH) (2, 1.6%) and Streptomycin (STR) (2, 1.6%). There were two genotypically discordant RIF-resistant cases and one INH-resistant case. One case of pre-extensively drug-resistant TB (pre-XDR-TB) and one case of extensively drug-resistant TB (XDR-TB) were identified. The most frequent gene mutations associated with INH and rifampicin (RIF) resistance were observed in the katG MUT1 (S315T1) (20, 76.9%) and rpoB (S531L) (10, 52.6%) genes, respectively. Two MDR-TB isolates were resistant to second-line drugs; one had a mutation in the gyrA MUT1 gene, and the other had missing gyrA WT1, gyrA WT3, and rrs WT1 genes without any mutation. The detection of a significant proportion of DR-TB cases in this study suggests that DR-TB is a major public health problem in Ethiopia. Thus, we recommend the early detection and treatment of DR-TB and universal full first-line drug-susceptibility testing in routine system.

Tuberculosis Elimination in India: Where the Country Stands

Tuberculosis (TB) remains a significant public health challenge in India, with the country bearing the highest burden of TB cases globally. This article provides an overview of India's ongoing efforts towards TB elimination, highlighting both progress and persistent challenges. India's Revised National Tuberculosis Control Program (RNTCP), launched in 1997, has made remarkable strides in TB control. The introduction of the RNTCP and later its expansion as the National Tuberculosis Elimination Program (NTEP) in 2017, aimed to strengthen diagnostic and treatment services, with a focus on achieving universal access to TB care. DOTS (Directly Observed Treatment, Short-course) therapy has been a cornerstone of treatment, contributing to significant reductions in TB mortality. In recent years, India has made strides in adopting new technologies, including molecular diagnostics and telemedicine, to enhance TB case detection and patient care. The introduction of Bedaquiline and Delamanid, novel drugs for drug-resistant TB, has offered hope for patients with more resistant forms of the disease. However, the road to TB elimination in India is not without challenges. There is a pressing need for improved healthcare infrastructure, reduced stigma, and increased awareness among both the public and healthcare providers. The emergence of drug-resistant TB and the impact of the COVID-19 pandemic on TB services have posed additional hurdles. India's journey toward TB elimination is marked by significant progress and continued challenges. To achieve the ambitious goal of eliminating TB by 2025, concerted efforts are required to strengthen healthcare systems, improve diagnostic capabilities, and address social determinants of the disease.

Modeling and bifurcation analysis of tuberculosis with the multidrug-resistant compartment incorporating chemoprophylaxis treatment

Tuberculosis is a major health problem that contributes significantly to infectious disease mortality worldwide. A new challenge for society that demands extensive work toward implementing the right control strategies for Tuberculosis (TB) is the emergence of drug-resistant TB. In this study, we developed a mathematical model to investigate the effect of chemoprophylaxis treatment on the transmission of tuberculosis with the drug-resistant compartment. An analysis of stabilities is performed along with an investigation into the possibility of endemic and disease-free equilibrium. The qualitative outcome of the model analysis shows that Disease Free Equilibrium (DFE) is locally asymptotically stable for R0 < 1, but the endemic equilibrium becomes globally asymptotically stable for R0 > 1. A bifurcation analysis was performed using the center manifold theorem, and it was found that the model shows evidence of forward bifurcation. Furthermore, the sensitivity analysis of the model was thoroughly carried out, and numerical simulation was also performed. This study showed that administering chemoprophylaxis treatment to individuals with latent infections significantly reduces the progression of exposed individuals to the infectious and drug-resistant classes, ultimately leading to a reduction in the transmission of the disease at large.

Advancing tuberculosis management: the role of predictive, preventive, and personalized medicine.

Tuberculosis is a major global health issue, with approximately 10 million people falling ill and 1.4 million dying yearly. One of the most significant challenges to public health is the emergence of drug-resistant tuberculosis. For the last half-century, treating tuberculosis has adhered to a uniform management strategy in most patients. However, treatment ineffectiveness in some individuals with pulmonary tuberculosis presents a major challenge to the global tuberculosis control initiative. Unfavorable outcomes of tuberculosis treatment (including mortality, treatment failure, loss of follow-up, and unevaluated cases) may result in increased transmission of tuberculosis and the emergence of drug-resistant strains. Treatment failure may occur due to drug-resistant strains, non-adherence to medication, inadequate absorption of drugs, or low-quality healthcare. Identifying the underlying cause and adjusting the treatment accordingly to address treatment failure is important. This is where approaches such as artificial intelligence, genetic screening, and whole genome sequencing can play a critical role. In this review, we suggest a set of particular clinical applications of these approaches, which might have the potential to influence decisions regarding the clinical management of tuberculosis patients.

Molecular and cellular remodeling of HepG2 cells upon treatment with antitubercular drugs.

Drug-induced liver injury (DILI) is an adverse outcome of the currently used tuberculosis treatment regimen, which results in patient noncompliance, poor treatment outcomes, and the emergence of drug-resistant tuberculosis. DILI is primarily caused by the toxicity of the drugs and their metabolites, which affect liver cells, biliary epithelial cells, and liver vasculature. However, the precise mechanism behind the cellular damage attributable to first-line antitubercular drugs (ATDs), as well as the effect of toxicity on the cell survival strategies, is yet to be elucidated. In the current study, HepG2 cells upon treatment with a high concentration of ATDs showed increased perforation within the cell, cuboidal shape, and membrane blebbing as compared with control/untreated cells. It was observed that ATD-induced toxicity in HepG2 cells leads to altered mitochondrial membrane permeability, which was depicted by the decreased fluorescence intensity of the MitoRed tracker dye at higher drug concentrations. In addition, high doses of ATDs caused cell damage through an increase in reactive oxygen species production in HepG2 cells and a simultaneous reduction in glutathione levels. Further, high dose of isoniazid (50-200 mM), pyrazinamide (50-200 mM), and rifampicin (20-100 µM) causes cell apoptosis and affects cell survival during toxic conditions by decreasing the expression of potent autophagy markers Atg5, Atg7, and LC3B. Thus, ATD-mediated toxicity contributes to the reduced ability of hepatocytes to tolerate cellular damage caused by altered mitochondrial membrane permeability, increased apoptosis, and decreased autophagy. These findings further emphasize the need to develop adjuvant therapies that can mitigate ATD-induced toxicity for the effective treatment of tuberculosis.

Discovery of natural-product-derived sequanamycins as potent oral anti-tuberculosis agents.

The emergence of drug-resistant tuberculosis has created an urgent need for new anti-tubercular agents. Here, we report the discovery of a series of macrolides called sequanamycins with outstanding invitro and invivo activity against Mycobacterium tuberculosis (Mtb). Sequanamycins are bacterial ribosome inhibitors that interact with the ribosome in a similar manner to classic macrolides like erythromycin and clarithromycin, but with binding characteristics that allow them to overcome the inherent macrolide resistance of Mtb. Structures of the ribosome with bound inhibitors were used to optimize sequanamycin to produce the advanced lead compound SEQ-9. SEQ-9 was efficacious in mouse models of acute and chronic TB as a single agent, and it demonstrated bactericidal activity in a murine TB infection model in combination with other TB drugs. These results support further investigation of this series as TB clinical candidates, with the potential for use in new regimens against drug-susceptible and drug-resistant TB.

A host blood transcriptional signature differentiates multi-drug/rifampin-resistant tuberculosis (MDR/RR-TB) from drug susceptible tuberculosis: a pilot study.

Tuberculosis (TB), caused by the bacterium Mycobacterium tuberculosis is one of the top thirteen causes of death worldwide. The major challenge to control TB is the emergence of drug-resistant tuberculosis (DR-TB); specifically, multi-drug resistant TB which are resistant to the most potent drugs; rifampin and isoniazid. Owing to the inconsistencies of the current diagnostic methods, a single test cannot identify the whole spectrum of DR-TB associated mutations. Recently, host blood transcriptomics has gained attention as a promising technique that develops disease-specific RNA signatures/biomarkers. However, studies on host transcriptomics infected with DR-TB is limited. Herein, we intended to identify genes/pathways that are differentially expressed in multi-drug/rifampin resistant TB (MDR/RR-TB) in contrast to drug susceptible TB. We conducted blood RNA sequencing of 10 pulmonary TB patients (4; drug susceptible and 6; DR-TB) and 55 genes that were differentially expressed in MDR/RR-TB from drug-susceptible/mono-resistant TB were identified. CD300LD, MYL9, VAMP5, CARD17, CLEC2B, GBP6, BATF2, ETV7, IFI27 and FCGR1CP were found to be upregulated in MDR/RR-TB in all comparisons, among which CLEC2B and CD300LD were not previously linked to TB. In comparison pathway analysis, interferon alpha/gamma response was upregulated while Wnt/beta catenin signaling, lysosome, microtubule nucleation and notch signaling were downregulated. Up/down-regulation of immunity related genes/pathways speculate the collective effect of hosts' attempt to fight against continuously multiplying DR-TB bacteria and the bacterial factors to fight against the host defense. The identified genes/pathways could act as MDR/RR-TB biomarkers, hence, further research on their clinical use should be encouraged.

Ultrasensitive Detection of Multidrug-Resistant Mycobacterium tuberculosis Using SuperSelective Primer-Based Real-Time PCR Assays

The emergence of drug-resistant tuberculosis is a significant global health issue. The presence of heteroresistant Mycobacterium tuberculosis is critical to developing fully drug-resistant tuberculosis cases. The currently available molecular techniques may detect one copy of mutant bacterial genomic DNA in the presence of about 1-1000 copies of wild-type M. tuberculosis DNA. To improve the limit of heteroresistance detection, we developed SuperSelective primer-based real-time PCR assays, which, by their unique assay design, enable selective and exponential amplification of selected point mutations in the presence of abundant wild-type DNA. We designed SuperSelective primers to detect genetic mutations associated with M. tuberculosis resistance to the anti-tuberculosis drugs isoniazid and rifampin. We evaluated the efficiency of our assay in detecting heteroresistant M. tuberculosis strains using genomic DNA isolated from laboratory strains and clinical isolates from the sputum of tuberculosis patients. Results show that our assays detected heteroresistant mutations with a specificity of 100% in a background of up to 104 copies of wild-type M. tuberculosis genomic DNA, corresponding to a detection limit of 0.01%. Therefore, the SuperSelective primer-based RT-PCR assay is an ultrasensitive tool that can efficiently diagnose heteroresistant tuberculosis in clinical specimens and contributes to understanding the drug resistance mechanisms. This approach can improve the management of antimicrobial resistance in tuberculosis and other infectious diseases.

Host-Directed Therapies for Tuberculosis.

Tuberculosis (TB) is one of the leading causes of death worldwide, consistently threatening public health. Conventional tuberculosis treatment requires a long-term treatment regimen and is associated with side effects. The efficacy of antitubercular drugs has decreased with the emergence of drug-resistant TB; therefore, the development of new TB treatment strategies is urgently needed. In this context, we present host-directed therapy (HDT) as an alternative to current tuberculosis therapy. Unlike antitubercular drugs that directly target Mycobacterium tuberculosis (Mtb), the causative agent of TB, HDT is an approach for treating TB that appropriately modulates host immune responses. HDT primarily aims to enhance the antimicrobial activity of the host in order to control Mtb infection and attenuate excessive inflammation in order to minimize tissue damage. Recently, research based on the repositioning of drugs for use in HDT has been in progress. Based on the overall immune responses against Mtb infection and the immune-evasion mechanisms of Mtb, this review examines the repositioned drugs available for HDT and their mechanisms of action.

NSC19723, a Thiacetazone-Like Benzaldehyde Thiosemicarbazone Improves the Efficacy of TB Drugs In Vitro and In Vivo.

The complexity and duration of tuberculosis (TB) treatment contributes to the emergence of drug resistant tuberculosis (DR-TB) and drug-associated side effects. Alternate chemotherapeutic agents are needed to shorten the time and improve efficacy of current treatment. In this study, we have assessed the antitubercular activity of NSC19723, a benzaldehyde thiosemicarbazone molecule. NSC19723 is structurally similar to thiacetazone (TAC), a second-line anti-TB drug used to treat individuals with DR-TB. NSC19723 displayed better MIC values than TAC against Mycobacterium tuberculosis and Mycobacterium bovis BCG. In our checkerboard experiments, NSC19723 displayed better profiles than TAC in combination with known first-line and recently approved drugs. Mechanistic studies revealed that NSC19723 inhibits mycolic acid biosynthesis by targeting the HadABC complex. Computational studies revealed that the binding pocket of HadAB is similarly occupied by NSC19723 and TAC. NSC19723 also improved the efficacy of isoniazid in macrophages and mouse models of infection. Cumulatively, we have identified a benzaldehyde thiosemicarbazone scaffold that improved the activity of TB drugs in liquid cultures, macrophages, and mice. IMPORTANCE Mycobacterium tuberculosis, the causative agent of TB is among the leading causes of death among infectious diseases in humans. This situation has worsened due to the failure of BCG vaccines and the increased number of cases with HIV-TB coinfections and drug-resistant strains. Another challenge in the field is the lengthy duration of therapy for drug-sensitive and -resistant TB. Here, we have deciphered the mechanism of action of NSC19723, benzaldehyde thiosemicarbazone. We show that NSC19723 targets HadABC complex and inhibits mycolic acid biosynthesis. We also show that NSC19723 enhances the activity of known drugs in liquid cultures, macrophages, and mice. We have also performed molecular docking studies to identify the interacting residues of HadAB with NSC19723. Taken together, we demonstrate that NSC19723, a benzaldehyde thiosemicarbazone, has better antitubercular activity than thiacetazone.

CRISPR-Based Diagnostics: A Potential Tool to Address the Diagnostic Challenges of Tuberculosis.

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis, which infects more than 23% of the world’s population. With the emergence of drug-resistant TB (DR-TB) and latent TB infection (LTBI), rapid diagnosis of DR-TB and LTBI has become a challenge for the prevention and control of TB. Herein, we highlight these challenges and discuss emerging clustered regularly interspaced short palindromic repeats (CRISPR)-based diagnostics in TB detection. Currently, the clinical diagnosis of M. tuberculosis infection mainly depends on pathogenic and molecular biological methods, including sputum smear, sputum culture, and Xpert. Although CRISPR-based diagnostics have not been applied to the clinical diagnosis of TB, they have shown exciting preponderances in TB diagnosis compared with traditional methods, including higher sensitivity, less sample input, and shorter turnaround time. CRISPR-based diagnostics represent a potential tool to address the challenges and natural weaknesses associated with traditional TB diagnosis methods. Based on the currently available data, we suggest that future CRISPR-based TB diagnostics should be developed in the direction of automation, modularization, diversification, and intelligence. By combining the CRISPR platform with various systems, such as microfluidic chips, droplet microfluidics, electrochemical techniques, and optical systems, the specificity and sensitivity of TB diagnosis may be revolutionized.

Genome-wide association studies of global Mycobacterium tuberculosis resistance to 13 antimicrobials in 10,228 genomes identify new resistance mechanisms.

The emergence of drug-resistant tuberculosis is a major global public health concern that threatens the ability to control the disease. Whole-genome sequencing as a tool to rapidly diagnose resistant infections can transform patient treatment and clinical practice. While resistance mechanisms are well understood for some drugs, there are likely many mechanisms yet to be uncovered, particularly for new and repurposed drugs. We sequenced 10,228 Mycobacterium tuberculosis (MTB) isolates worldwide and determined the minimum inhibitory concentration (MIC) on a grid of 2-fold concentration dilutions for 13 antimicrobials using quantitative microtiter plate assays. We performed oligopeptide- and oligonucleotide-based genome-wide association studies using linear mixed models to discover resistance-conferring mechanisms not currently catalogued. Use of MIC over binary resistance phenotypes increased sample heritability for the new and repurposed drugs by 26% to 37%, increasing our ability to detect novel associations. For all drugs, we discovered uncatalogued variants associated with MIC, including in the Rv1218c promoter binding site of the transcriptional repressor Rv1219c (isoniazid), upstream of the vapBC20 operon that cleaves 23S rRNA (linezolid) and in the region encoding an α-helix lining the active site of Cyp142 (clofazimine, all p < 10−7.7). We observed that artefactual signals of cross-resistance could be unravelled based on the relative effect size on MIC. Our study demonstrates the ability of very large-scale studies to substantially improve our knowledge of genetic variants associated with antimicrobial resistance in M. tuberculosis.

Drug Resistance Patterns and Trends in Patients with Suspected Drug-Resistant Tuberculosis in Dalian, China: A Retrospective Study.

PurposeThe emergence of drug-resistant tuberculosis (DR-TB) represents a threat to the control of tuberculosis. This study aimed to estimate the patterns and trends of DR-TB in patients with suspected DR-TB. In addition, risk factors for multidrug-resistant tuberculosis (MDR-TB) were identified among suspected DR-TB patients in Dalian, China.Patients and MethodsA total of 5661 patients with suspected DR-TB from Jan 1, 2013 to Dec 31, 2020 were included in the final analysis. The resistance pattern of all resistant strains was determined by drug susceptibility testing (DST) using the conventional Lowenstein-Jensen Proportion Method (LJ). DR-TB trends were estimated from 2013 to 2020. During the research period, the chi-square test was employed to analyze the significance of linear drug-resistance trends across time. Bivariate and multivariate logistic regression were performed to assess factors associated with MDR-TB.ResultsFrom 2013 to 2020, the resistance rates of rifampicin (RFP) and isoniazid (INH) decreased significantly, whereas the resistance rates of ethambutol (EMB) and streptomycin (SM) increased in patients with suspected DR-TB. From 2013 to 2020, the prevalence of DR-TB decreased in all patients from 34.71% to 28.01% with an average annual decrease of 3.02%. Among new cases, from 2013 to 2020, the prevalence of DR-TB (from 26.67% to 24.75%), RFP-resistant TB (RR-TB) (from 15.09% to 3.00%) and MDR-TB (from 6.08% to 2.62%) showed a significant downward trend. Among patients with a previous treatment history, DR-TB (from 54.70% to 37.50%), RR-TB (from 44.16% to 11.49%) and MDR-TB (from 26.90% to 10.34%) showed a significant downward trend from 2013 to 2020. Males (AOR 1.28, 95% CI 1.035–1.585), patients 45 to 64 years of age (AOR 1.75, 95% CI 1.342–2.284), patients 65 years and older (AOR 1.65, 95% CI 1.293–2.104), rural residents (AOR 1.24, 95% CI 1.014–1.519) and a previous treatment history (AOR 3.94, 95% CI 3.275–4.741) were risk factors for MDR-TB.ConclusionThe prevalence of DR-TB, RR-TB and MDR-TB was significantly reduced from 2013 to 2020. Considerable progress has been made in the prevention and treatment of DR-TB during this period. However, the increasing rate of drug resistance in EMB and SM should be taken seriously. Suspected DR-TB patients who are male, older than 45 years of age, live in rural areas, and have a history of TB treatment should be given priority by health care providers.

Risk factors associated with drug-resistant tuberculosis in Ethiopia: A systematic review and meta-analysis.

The emergence of drug-resistant tuberculosis (DR-TB) is becoming a challenge to the national TB control programmes including Ethiopia. Different risk factors are associated with DR-TB. Identifying these risk factors in a local setting is important to strengthen the effort to prevent and control DR-TB. Thus, this study aimed to assess the risk factors associated with DR-TB in Ethiopia. The Preferred Reporting Items for Systematic Reviews and Meta-analyses checklist was followed to conduct this study. We systematically searched the articles from electronic databases and grey literature sources. We used the JBI tools to assess the quality of studies. Data were analysed using STATA version 15. We estimated the pooled odds ratio (OR) along with 95% Confidence Interval (CI). The forest plot and I2 heterogeneity test were used to assess heterogeneity among studies. We explored the presence of publication bias through visual inspection of the funnel plot and Egger's regression test. After screening 2238 articles, 27 studies were included in the final analysis. Based on the pooled analysis of the OR, unemployment (OR; 2.71, 95% CI; 1.64, 3.78), previous TB history (OR; 4.83, 95% CI; 3.02, 6.64), contact with known TB patient (OR; 1.72, 95% CI; 1.05, 2.40), contact with the known multi-drug resistant (MDR) TB patient (OR; 2.54, 95% CI; 1.46, 3.63) and having pulmonary TB (PTB; OR; 1.80, 95% CI; 1.14, 2.45) were found to be the risk factors of DR-TB, while elders (OR; 0.77, 95%CI; 0.60, 0.95) including above 45 years (OR; 0.76, 95%CI; 0.55, 0.97) and males (OR; 0.86, 95%CI; 0.76, 0.97) had lower DR-TB risk, compared to their counterparts. A previous history of TB treatment is a major risk factor for acquiring DR-TB in Ethiopia that might be due to poor adherence during the first-line anti-TB treatment. Besides, having contact with a TB patient, contact with an MDR-TB patient, having PTB and being unemployed were the risk factors of DR-TB in Ethiopia. Thus, active screening of TB contacts for DR-TB might help to detect DR-TB cases as early as possible and could help to mitigate its further transmission across the community.

Novel mutations detected from drug resistant Mycobacterium tuberculosis isolated from North East of Thailand.

The emergence of drug-resistant tuberculosis is a major global public health threat. Thailand is one of the top 14 countries with high tuberculosis and multi-drug resistant tuberculosis rates. Immediate detection of drug-resistant tuberculosis is necessary to reduce mortality and morbidity by effectively providing treatment to ameliorate the formation of resistant strains. Limited data exist of mutation profiles in Northeastern Thailand. Here, 65 drug-resistant Mycobacterium tuberculosis isolates were used to detect mutations by polymerase chain reaction (PCR) and DNA sequencing. In the katG gene, mutations were occurred in 47 (79.7%) among 59 isoniazid resistant samples. For rpoB gene, 31 (96.9%) were observed as mutations in 32 rifampicin resistant isolates. Of 47 katG mutation samples, 45 (95.7%) had mutations in katG315 codon and 2 (4.3%) showed novel mutations at katG365 with amino acid substitution of CCG-CGG (Pro-Arg). Moreover, out of 31 rpoB mutation isolates, the codon positions rpoB516, rpoB526, rpoB531 and rpoB533 were 3 (9.7%), 8 (25.8%), 11 (35.5%) and 1 (3.2%), respectively. Seven isolates of double point mutation were found [rpoB516, 526; 1 (3.2%) and rpoB516, 531; 6 (19.4%)]. In addition, 1 (3.2%) sample had triple point mutation at codon positions rpoB516, 526 and 531. Common and novel mutation codons of the rpoB and katG genes were generated. Although DNA sequencing showed high accuracy, conventional PCR could be applied as an initial marker for screening drug-resistant Mycobacterium tuberculosis isolates in limit resources region. Mutations reported here should be considered when developing new molecular diagnostic methods for implementation in Northeastern Thailand.