Whole-genome sequencing for surveillance of tuberculosis drug resistance and determination of resistance level in China

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.

Drug-Resistant Profiles and Genetic Diversity of Mycobacterium Tuberculosis Revealed by Whole-Genome Sequencing in Hinggan League of Inner Mongolia, China

Background

Tuberculosis remains a major public health concern in China, with varying prevalence and drug resistance profiles across regions. This study explores the genetic diversity and drug-resistant profiles of MTB strains in Hinggan League, a high TB burden in Inner Mongolia, China.

Methods

This population-based retrospective study, encompassing all culture-positive TB cases from Jun. 2021 to Jun. 2023 in Hinggan League. Drug resistant profiles and genetic diversity of MTB strains were assessed using phenotypic drug susceptibility testing and whole-genome sequencing. Risk factors associated with drug resistance were analyzed using univariate and multivariate logistic regression models.

Results

A total of 211 MTB strains were recovered successfully and included into final analysis. Lineage 2.2.1 (88.6%, 187/211) was the dominant sub-lineage, followed by lineage 4.5 (7.1%, 15/211) and lineage 4.4 (4.3%, 9/211). MTB strains exhibited the highest resistance rates to isoniazid (16.1%, 34/211), followed by rifampicin (10.0, 21/211). In addition, the MTB strains also showed relatively high rates of resistance against new and repurposed anti-TB drugs, with resistant rates of 2.4% (5/211) to delamanid and 1.9% (4/211) to bedaquiline. Overall, 25.6% (54/211) of MTB strains were DR-TB, and 14 MTB strains met the definition of MDR-TB, including 7 strains of simple-MDR-TB, 5 of pre-XDR-TB, and 2 of XDR-TB. Genetic analysis revealed that the dominant mutations of isoniazid-, rifampin-, ethambutol-, levofloxacin-/moxifloxacin-, and ethionamide- resistance were katG_Ser315Thr(46.4%), rpoB_Ser450Leu (47.4%), embB_Met306Val (25.0%), gyrA_Asp94Ala (40.0%), and fabG1_c15t (42.9%), respectively. Previously treated patients (AOR = 2.015, 95% CI: 1.052-4.210) and male patients (AOR = 3.858, 95% CI: 1.416-10.511) were identified as independent risk factors associated with DR-TB.

Conclusion

Our study offers crucial insights into the genetic diversity and drug-resistant profiles of TB strains circulating in Hinggan League. These findings are valuable for DR-TB surveillance and for guiding treatment regimens and public health interventions in the region.

Optimization of Mycobacterium tuberculosis DNA processing prior to whole genome sequencing

The process of whole genome sequencing of the Mycobacterium tuberculosis complex is dependent on complete the inactivation of the strain and subsequent DNA extraction. The objective of this study was to optimise the two steps. Firstly, the efficacy of Triton X-100 as a solvent for the inactivation step was evaluated. This solvent has been demonstrated to be effective in killing bacteria and is less toxic than the previously employed chloroform. For the extraction step, two lysis methods were evaluated: enzymatic (B1 protocol) and mechanical (B2 protocol). For whole genome sequencing, the Nextera XT DNA library preparation protocol was performed for both the B1 and B2 protocols. Subsequently, each library was subjected to whole-genome sequencing. The results demonstrated that heat lysis inactivation with Triton was effective, with no bacteria remaining viable following this treatment. The enzymatic and mechanical extraction protocols yielded comparable results in terms of DNA quantity and quality. The sequencing results showed that there was no significant difference in read depths between the two protocols. In conclusion, for MTBC strains, we recommend the use of our Triton inactivation method, which meets biosafety expectations.

Mutations in embB406 Are Associated with Low-Level Ethambutol Resistance in Canadian Mycobacterium tuberculosis Isolates

In Mycobacterium tuberculosis, molecular predictions of ethambutol resistance rely primarily on the detection of mutations within embB. However, discordance between embB406 mutations and gold standard phenotypic drug sensitivity testing (DST) questions the significance of embB406 mutations used in molecular DST. This study tabulates embB mutations found in Canadian M. tuberculosis isolates and evaluates the impact of specific mutations on ethambutol resistance. The National Reference Centre for Mycobacteriology culture collection (n = 2796) was screened for isolates with embB mutations. Phenotypic DST was performed on the BACTEC™ MGIT™ 960 at ethambutol concentrations of 2-5 μg/mL. Whole genome sequencing was used for drug resistance predictions, phylogenomics and single nucleotide polymorphism analysis. Detection of resistance-associated embB mutations corresponded to a positive predictive value of 64.3%, negative predictive value of 99.2%, 98.7% specificity, and 73.3% sensitivity compared to phenotypic DST. Two embB406 mutation subtypes (Gly406Asp, Gly406Ala) were found among 16 isolates, of which 12 were sensitive at 5 µg/mL ethambutol with variable resistance between 2-4 µg/mL. A novel frameshift mutation in regulator embR (Gln258fs) was found in nine isolates. Mutations in embB406 were associated with low-level ethambutol resistance undetectable at the recommended critical concentration (5 μg/mL). These novel mutations may exacerbate variability in ethambutol resistance.

Drug-Resistant Characteristics, Genetic Diversity, and Transmission Dynamics of Multidrug-Resistant Mycobacterium tuberculosis in Jiangxi, China

Purpose

In this study, we aimed to determine the transmission pattern of multidrug-resistant tuberculosis (MDR-TB) isolates circulating in Jiangxi Province with whole-genome sequencing (WGS). In addition, we also sought to describe mutational resistome of MDR-TB isolates.

Patients and Methods

A total of 115 MDR-TB isolates determined by the phenotypic proportion method of drug susceptibility testing between January 2018 and December 2022 from provincial drug surveillance (DRS) in Jiangxi were included in our analysis. The demographic data and treatment history were extracted from the National TB Registry System. WGS was used to analyze the genotypic characteristics of drug resistance and transmissions.

Results

About 62.6% of MDR-TB strains were isolated from cases that received previous anti-tuberculosis treatment. According to the WGS results, 96.5% were genotypic MDR-TB, and more than half of MDR-TB isolates tested were also resistant to streptomycin (59.1%), ethambutol (56.5%), and fluroquinolones (53.0%), while resistance to cycloserine and linezolid was lowest, only in two (1.7%) and one (0.9%) isolate, respectively. Ser450Leu in rpoB (57.9%), Ser315Thr in katG (74.1%), Met306Val in embB (40.0%), Lys43Arg in rpsL (75.0%), Ala90Val in gyrA (32.8%) were predominant mutant types among the rifampin-, isoniazid-, ethambutol-, streptomycin-, fluoroquinolones-resistant isolates, respectively. Lineage 2 (East Asian genotype) occurred at the highest frequency with 97 cases (84.3%), followed by lineage 4 (Euro-American genotype) with 18 cases (15.7%). Additionally, 5 clusters consisting of 10 isolates were identified in the present study, demonstrating a clustering rate of 8.7%.

Conclusion

MDR/Rifampicin-Resistant (RR)-TB epidemic in this region is driven by lineage 2 clade that also show higher resistance to other anti-tuberculosis drugs. Lower cluster rates compared with a relatively higher proportion of new MDR-TB cases indicate that a considerable number of MDR-TB cases remain undiagnosed.

Exploring diagnostic methods for drug-resistant tuberculosis: A comprehensive overview

Despite available global efforts and funding, Tuberculosis (TB) continues to affect a considerable number of patients worldwide. Policy makers and stakeholders set clear goals to reduce TB incidence and mortality, but the emergence of multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB) complicate the reach of these goals. Drug-resistance TB needs to be diagnosed rapidly and accurately to effectively treat patients, prevent the transmission of MDR-TB, minimise mortality, reduce treatment costs and avoid unnecessary hospitalisations. In this narrative review, we provide a comprehensive overview of laboratory methods for detecting drug resistance in MTB, focusing on phenotypic, molecular and other drug susceptibility testing (DST) techniques. We found a large variety of methods used, with the BACTEC MGIT 960 being the most common phenotypic DST and the Xpert MTB/RIF being the most common molecular DST. We emphasise the importance of integrating phenotypic and molecular DST to address issues like resistance to new drugs, heteroresistance, mixed infections and low-level resistance mutations. Notably, most of the analysed studies adhered to the outdated definition of XDR-TB and did not consider the pre-XDR definition, thus posing challenges in aligning diagnostic methods with the current landscape of TB resistance.

High-throughput nanopore targeted sequencing for efficient drug resistance assay of Mycobacterium tuberculosis

Drug-resistant tuberculosis (TB), especially multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB), is one of the urgent clinical problems and public health challenges. Culture-based phenotypic drug susceptibility testing (pDST) is time-consuming, and PCR-based assays are limited to hotspot mutations. In this study, we developed and validated a convenient and efficient approach based on high-throughput nanopore sequencing technology combined with multiplex PCR, namely nanopore targeted sequencing (NTS), to simultaneously sequence 18 genes associated with antibiotic resistance in Mycobacterium tuberculosis (MTB). The analytical performance of NTS was evaluated, and 99 clinical samples were collected to assess its clinical performance. The NTS results showed that MTB and its drug resistance were successfully identified in approximately 7.5 h. Furthermore, compared to the pDST and Xpert MTB/RIF assays, NTS provided much more drug resistance information, covering 14 anti-TB drugs, and it identified 20 clinical cases of drug-resistant MTB. The mutations underlying these drug-resistant cases were all verified using Sanger sequencing. Our approach for this TB drug resistance assay offers several advantages, including being culture-free, efficient, high-throughput, and highly accurate, which would be very helpful for clinical patient management and TB infection control.

Prevalence and genetic basis of Mycobacterium tuberculosis resistance to pretomanid in China

BACKGROUND

Pretomanid is a key component of new regimens for the treatment of drug-resistant tuberculosis (TB) which are being rolled out globally. However, there is limited information on the prevalence of pre-existing resistance to the drug.

METHODS

To investigate pretomanid resistance rates in China and its underlying genetic basis, as well as to generate additional minimum inhibitory concentration (MIC) data for epidemiological cutoff (ECOFF)/breakpoint setting, we performed MIC determinations in the Mycobacterial Growth Indicator Tube™ (MGIT) system, followed by WGS analysis, on 475 Mycobacterium tuberculosis (MTB) isolated from Chinese TB patients between 2013 and 2020.

RESULTS

We observed a pretomanid MIC distribution with a 99% ECOFF equal to 0.5 mg/L. Of the 15 isolates with MIC values > 0.5 mg/L, one (MIC = 1 mg/L) was identified as MTB lineage 1 (L1), a genotype previously reported to be intrinsically less susceptible to pretomanid, two were borderline resistant (MIC = 2-4 mg/L) and the remaining 12 isolates were highly resistant (MIC ≥ 16 mg/L) to the drug. Five resistant isolates did not harbor mutations in the known pretomanid resistant genes.

CONCLUSIONS

Our results further support a breakpoint of 0.5 mg/L for a non-L1 MTB population, which is characteristic of China. Further, our data point to an unexpected high (14/475, 3%) pre-existing pretomanid resistance rate in the country, as well as to the existence of yet-to-be-discovered pretomanid resistance genes.

Whole-genome sequencing of clinical isolates from tuberculosis patients in India: real-world data indicates a high proportion of pre-XDR cases

Treatment decisions for tuberculosis (TB) in the absence of full drug-susceptibility data can result in amplifying resistance and may compromise treatment outcomes. Genomics of Mycobacterium tuberculosis (M.tb) from clinical samples enables detection of drug resistance to multiple drugs. We performed whole-genome sequencing (WGS) for 600 clinical samples from patients with tuberculosis to identify the drug-resistance profile and mutation spectrum. We documented the reasons reported by clinicians for referral. WGS identified a high proportion (51%) of pre-extensively drug-resistant (pre-XDR) cases followed by multidrug-resistant tuberculosis (MDR-TB) (15.5%). This correlates with the primary reason for referral, as non-response to the first-line treatment (67%) and treatment failure or rifampicin resistance (14%). Multivariate analysis indicated that all young age groups (P < 0.05), male gender (P < 0.05), and Beijing strain (P < 0.01) were significant independent predictors of MDR-TB or MDR-TB+ [pre-extensively drug-resistant tuberculosis (XDR-TB) and XDR-TB]. Ser315Thr (72.5%) in the inhA gene and Ser450Leu in the rpoB gene (65.5%) were the most prevalent mutations, as were resistance-conferring mutations to pyrazinamide (41%) and streptomycin (61.33%). Mutations outside the rifampicin resistance-determining region (RRDR), Ile491Phe and Val170Phe, were seen in 1.3% of cases; disputed mutations in rpoB (Asp435Tyr, His445Asn, His445Leu, and Leu430Pro) were seen in 6% of cases, and mutations to newer drugs such as bedaquiline and linezolid in 1.0% and 7.5% of cases, respectively. This study on clinical samples highlights that there is a high proportion of pre-XDR cases and emerging resistance to newer drugs; ongoing transmission of these strains can cause serious threat to public health; and whole-genome sequencing can effectively identify and support precision medicine for TB.

IMPORTANCE

The current study is based on real-world data on the TB drug-resistance profile by whole-genome sequencing of 600 clinical samples from patients with TB in India. This study indicates the clinicians' reasons for sending samples for WGS, which is for difficult-to-treat cases and/or relapse and treatment failure. The study reports a significant proportion of cases with pre-XDR-TB strains that warrant policy makers' attention. It reflects the current iterative nature of the diagnostic tests under programmatic conditions that leads to delays in appropriate diagnosis and empirical treatment. India had an estimated burden of 2.95 million TB cases in 2020 and 135,000 multidrug-resistant cases. However, WGS profiles of M.tb from India remains disproportionately poorly represented. This study adds a significant body of data on the mutation profiles seen in M.tb isolated from patients with TB in India, mutations outside the RRDR, disputed mutations, and resistance-conferring mutations to newer drugs such as bedaquiline and linezolid.

Insidious transmission of Mycobacterium tuberculosis in Ordos, China: a molecular epidemiology study

BACKGROUND

In this study, we conducted this population-based study to evaluate the genetic diversity and clustering rate of Mycobacterium tuberculosis (MTB) strains using the whole-genome sequencing (WGS), to better understand its transmission in Ordos.

METHODS

All patients with culture-positive TB notified in Ordos from January 2021 to December 2022 were recruited. WGS was performed to analyze single-nucleotide polymorphism (SNP) and to identify genotypic drug susceptibilities of MTB isolates.

RESULTS

Overall, a total of 186 patients were included in the present study, of whom 35 (18.8%) had no symptoms suggestive of active TB. Lineage 2 was the predominant MTB sublineage, accounting for 186 of isolates tested. When the pairwise SNP difference ≤ 12 was used as the cutoff for WGS-based clusters, we identified 17 genotypic clusters, and 38 isolates belonged to these 17 clusters, resulting in a clustering rate of 20.4%. The Beijing genotype was an independent factor associating with genomic-clustering (adjusted OR 4.219, 95% CI 0.962-18.502). The overall sensitivity on WGS-based resistance prediction was 85.7% for rifampicin, 73.1% for isoniazid, 60.0% for Ethambutol, 72.7% for streptomycin, and 72.7% for fluoroquinolones.

CONCLUSION

To conclude, the present study demonstrates the extensive recent transmission of Beijing genotype strains in the community of Ordos. The failure to provide a comprehensive pattern of transmission indicated the missed diagnosis of active TB within the community. A substantial proportion of subclinical TB cases are recognized in the bacteria-positive cases, emphasizing that we must interrupt transmission by finding people with active TB before they infect others.

Diagnostic efficacy of an optimized nucleotide MALDI-TOF-MS assay for anti-tuberculosis drug resistance detection

PURPOSE

We aimed at evaluating the diagnostic efficacy of a nucleotide matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) assay to detect drug resistance of Mycobacterium tuberculosis.

METHODS

Overall, 263 M. tuberculosis clinical isolates were selected to evaluate the performance of nucleic MALDI-TOF-MS for rifampin (RIF), isoniazid (INH), ethambutol (EMB), moxifloxacin (MXF), streptomycin (SM), and pyrazinamide (PZA) resistance detection. The results for RIF, INH, EMB, and MXF were compared with phenotypic microbroth dilution drug susceptibility testing (DST) and whole-genome sequencing (WGS), and the results for SM and PZA were compared with those obtained by WGS.

RESULTS

Using DST as the gold standard, the sensitivity, specificity, and kappa values of the MALDI-TOF-MS assay for the detection of resistance were 98.2%, 98.7%, and 0.97 for RIF; 92.8%, 99%, and 0.90 for INH; 82.4%, 98.0%, and 0.82 for EMB; and 92.6%, 99.5%, and 0.94 for MXF, respectively. Compared with WGS as the reference standard, the sensitivity, specificity, and kappa values of the MALDI-TOF-MS assay for the detection of resistance were 97.4%, 100.0%, and 0.98 for RIF; 98.7%, 92.9%, and 0.92 for INH; 96.3%, 100.0%, and 0.98 for EMB; 98.1%, 100.0%, and 0.99 for MXF; 98.0%, 100.0%, and 0.98 for SM; and 50.0%, 100.0%, and 0.65 for PZA.

CONCLUSION

The nucleotide MALDI-TOF-MS assay yielded highly consistent results compared to DST and WGS, suggesting that it is a promising tool for the rapid detection of sensitivity to RIF, INH, EMB, and MXF.

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.

Exploring programmatic indicators of tuberculosis control that incorporate routine Mycobacterium tuberculosis sequencing in low incidence settings: a comprehensive (2017-2021) patient cohort analysis

Background

Routine whole genome sequencing of Mycobacterium tuberculosis has been implemented with increasing frequency. However, its value for tuberculosis (TB) control programs beyond individual case management and enhanced drug resistance detection has not yet been explored.

Methods

We analysed routine sequencing data of culture-confirmed TB cases notified between 1st January 2017 and 31st December 2021 in New South Wales (NSW), Australia. Genomic surveillance included evidence of local TB transmission, defined by single nucleotide polymorphism (SNP) clustering over a variable (0-25) SNP threshold, and drug resistance conferring mutations.

Findings

M. tuberculosis sequences from 1831 patients were examined, representing 64.8% of all notified TB cases and 96.2% of culture-confirmed cases. Applying a traditional 5-SNP cluster threshold identified 62 transmission clusters with 183 clustered cases; 101/183 (55.2%) had 0 SNP differences. Cluster assessment over a 5-year period, using a 5-SNP threshold, provided a comprehensive overview of likely recent transmission within NSW, Australia, as an indicator of local TB control. Genotypic drug susceptibility testing (DST) was highly concordant with phenotypic DST and provided a 6.8% increase in antimycobacterial resistance detection. Importantly, it detected mutations missed by routine molecular tests. Lineage 2 strains were more likely to be drug resistant (p < 0.0001) and locally transmitted if drug resistant (p < 0.0001).

Interpretation

Performing routine prospective WGS in a low incidence country like Australia, provides genomically informed programmatic indicators of local TB control. A rolling 5-year cluster assessment reflects epidemic containment and progress towards 'zero TB transmission'. Genomic DST also provides valuable information for clinical care and drug resistance surveillance.

Funding

NHMRC Centre for Research Excellence in Tuberculosis (www.tbcre.org.au) and NSW Health Prevention Research Support Program.

Deep learning on longitudinal CT scans: automated prediction of treatment outcomes in hospitalized tuberculosis patients

Three deep learning (DL)-based prediction models (PMs) using longitudinal CT images were developed to predict tuberculosis (TB) treatment outcomes. The internal dataset consists of 493 bacteriologically confirmed TB patients who completed the anti-tuberculosis treatment with three-time CT scans, including a pretreatment CT scan and two follow-up CT scans. PM1 was trained using only pretreatment CT scans, and PM2 and PM3 were developed by adding follow-up scans. An independent testing was performed on external dataset comprising 86 TB patients. The area under the curve for classifying success and drug-resistant (DR)-TB was improved on both internal (0.609 vs. 0.625 vs. 0.815) and external (0.627 vs. 0.705 vs. 0.735) dataset by adding follow-up scans. The accuracy and F1-score also showed an increasing tendency in the external test. Regular follow-up CT scans can aid in the treatment prediction, and special attention should be given to early intensive phase of treatment to identify high-risk DR-TB patients.

Genotypic and phenotypic comparison of drug resistance profiles of clinical multidrug-resistant Mycobacterium tuberculosis isolates using whole genome sequencing in Latvia

BACKGROUND

Multidrug-resistant tuberculosis (MDR-TB) remains a major public health problem in many high tuberculosis (TB) burden countries. Phenotypic drug susceptibility testing (DST) take several weeks or months to result, but line probe assays and Xpert/Rif Ultra assay detect a limited number of resistance conferring gene mutations. Whole genome sequencing (WGS) is an advanced molecular testing method which theoretically can predict the resistance of M. tuberculosis (Mtb) isolates to all anti-TB agents through a single analysis.

METHODS

Here, we aimed to identify the level of concordance between the phenotypic and WGS-based genotypic drug susceptibility (DS) patterns of MDR-TB isolates. Overall, data for 12 anti-TB medications were analyzed.

RESULTS

In total, 63 MDR-TB Mtb isolates were included in the analysis, representing 27.4% of the total number of MDR-TB cases in Latvia in 2012-2014. Among them, five different sublineages were detected, and 2.2.1 (Beijing group) and 4.3.3 (Latin American-Mediterranean group) were the most abundant. There were 100% agreement between phenotypic and genotypic DS pattern for isoniazid, rifampicin, and linezolid. High concordance rate (> 90%) between phenotypic and genotypic DST results was detected for ofloxacin (93.7%), pyrazinamide (93.7%) and streptomycin (95.4%). Phenotypic and genotypic DS patterns were poorly correlated for ethionamide (agreement 56.4%), ethambutol (85.7%), amikacin (82.5%), capreomycin (81.0%), kanamycin (85.4%), and moxifloxacin (77.8%). For capreomycin, resistance conferring mutations were not identified in several phenotypically resistant isolates, and, in contrary, for ethionamide, ethambutol, amikacin, kanamycin, and moxifloxacin the resistance-related mutations were identified in several phenotypically sensitive isolates.

CONCLUSIONS

WGS is a valuable tool for rapid genotypic DST for all anti-TB agents. For isoniazid and rifampicin phenotypic DST potentially can be replaced by genotypic DST based on 100% agreement between the tests. However, discrepant results for other anti-TB agents limit their prescription based solely on WGS data. For clinical decision, at the current level of knowledge, there is a need for combination of genotypic DST with modern, validated phenotypic DST methodologies for those medications which did not showed 100% agreement between the methods.

Comparative Study on Tuberculosis Drug Resistance and Molecular Detection Methods Among Different Mycobacterium Tuberculosis Lineages

Purpose

This study aims to compare drug resistance and detection efficacy across different Mycobacterium tuberculosis lineages, offering insights for precise treatment and molecular diagnosis.

Methods

161 strains of Mycobacterium tuberculosis (M.tb) were tested for drug resistance using Phenotypic Drug Susceptibility Testing (pDST), High-Resolution Melting analysis (HRM), and Whole Genome Sequencing (WGS) methods. The main focus was on evaluating the accuracy of different methods for detecting resistance to rifampicin (RIF), isoniazid (INH), and streptomycin (SM).

Results

Among the 161 strains of M.tb, 83.85% (135/161) were fully sensitive to RIF, INH, and SM according to pDST, and the rate of multidrug resistance was 4.35% (7/161). The drug resistance rates of lineage 2 M.tb to the three drugs (26/219, 11.87%) were significantly higher than those of non-lineage 2 M.tb (12/264, 4.45%) (P<0.05). Compared with pDST, WGS had a sensitivity of 100%, 94.12%, and 92.31% and a specificity of 100%, 99.31%, and 98.65% for RIF, INH, and SM, respectively, with no significant difference. The sensitivity of HRM for RIF, INH, and SM was 87.50%, 52.94%, and 76.92%, respectively, while the specificity was 96.08%, 99.31%, and 99.32%, respectively. The sensitivity of HRM for detecting INH resistance was significantly lower than that of pDST (P=0.039). Compared with HRM, WGS increased the sensitivity of RIF, INH, and SM by 12.50%, 41.18%, and 15.38%, respectively.

Conclusion

There are significant differences in drug resistance rates among different lineages of M.tb, with lineage 2 having higher rates of RIF, INH, and SM resistance than lineages 3 and 4. The sensitivity of HRM is far lower than that of pDST, and currently, the accuracy of HRM is not sufficient to replace pDST. WGS has no significant difference in detecting drug resistance compared with pDST but can identify new anti-tuberculosis drug-resistant mutations, providing effective guidance for clinical decision-making.

Genetic Characterization Conferred Co-Resistance to Isoniazid and Ethionamide in Mycobacterium tuberculosis Isolates from Southern Xinjiang, China

Background

Ethionamide (ETH), a structural analogue of isoniazid (INH), is used for treating multidrug-resistant tuberculosis (MDR-TB). Due to the common target InhA, INH and ETH showed cross-resistance in M. tuberculosis. This study aimed to explore the INH and ETH resistant profiles and genetic mutations conferring independent INH- or ETH-resistance and INH-ETH cross-resistance in M. tuberculosis circulating in south of Xinjiang, China.

Methods

From Sep 2017 to Dec 2018, 312 isolates were included using drug susceptibility testing (DST), spoligotyping, and whole genome sequencing (WGS) to analyze the resistance characteristics for INH and/or ETH.

Results

Among the 312 isolates, 185 (58.3%) and 127 (40.7%) belonged to the Beijing family and non-Beijing family, respectively; 90 (28.9%) were INH-resistant (INH^R) with mutation rates of 74.4% in katG, 13.3% in inhA and its promoter, 11.1% in ahpC and its upstream region, 2.2% in ndh, 0.0% in mshA, whilst 34 (10.9%) were ETH-resistant (ETH^R) with mutation rates of 38.2% in ethA, 26.2% in inhA and its promoter, and 5.9% in ndh, 0.0% in ethR or mshA; and 25 (8.0%) were INH-ETH co-resistant (INH^RETH^R) with mutation rates of 40.0% in inhA and its promoter, and 8% in ndh. katG mutants tended to display high-level resistant to INH; and more inhA and its promoter mutants showed low-level of INH and ETH resistance. The optimal gene combinations by WGS for the prediction of INH^R, ETH^R, and INH^RETH^R were, respectively, katG+inhA and its promoter (sensitivity: 81.11%, specificity: 90.54%), ethA+inhA and its promoter+ndh (sensitivity: 61.76%, specificity: 76.62%), and inhA and its promoter+ndh (sensitivity: 48.00%, specificity: 97.65%).

Conclusion

This study revealed the high diversity of genetic mutations conferring INH and/or ETH resistance among M. tuberculosis isolates, which would facilitate the study on INH^R and/or ETH^R mechanisms and provide clues for choosing ETH for MDR treatment and molecular DST methods in south of Xinjiang, China.

Multiplex LNA probe-based RAP assay for rapid and highly sensitive detection of rifampicin-resistant Mycobacterium tuberculosis

Objectives

The World Health Organization (WHO) Global tuberculosis Report 2021 stated that rifampicin-resistant tuberculosis (RR-TB) remains a major public health threat. However, the in-practice diagnostic techniques for RR-TB have a variety of limitations including longer time, lack of sensitivity, and undetectable low proportion of heterogeneous drug resistance.

Methods

Here we developed a multiplex LNA probe-based RAP method (MLP-RAP) for more sensitive detection of multiple point mutations of the RR-TB and its heteroresistance. A total of 126 clinical isolates and 78 sputum samples collected from the National Tuberculosis Reference Laboratory, China CDC, were tested by MLP-RAP assay. In parallel, qPCR and Sanger sequencing of nested PCR product assay were also performed for comparison.

Results

The sensitivity of the MLP-RAP assay could reach 5 copies/μl using recombinant plasmids, which is 20 times more sensitive than qPCR (100 copies/μl). In addition, the detection ability of rifampicin heteroresistance was 5%. The MLP-RAP assay had low requirements (boiling method) for nucleic acid extraction and the reaction could be completed within 1 h when placed in a fluorescent qPCR instrument. The result of the clinical evaluation showed that the MLP-RAP method could cover codons 516, 526, 531, and 533 with good specificity. 41 out of 78 boiled sputum samples were detected positive by MLP-RAP assay, which was further confirmed by Sanger sequencing of nested PCR product assay, on the contrary, qPCR was able to detect 32 samples only. Compared with Sanger sequencing of nested PCR product assay, both the specificity and sensitivity of the MLP-RAP assay were 100%.

Conclusion

MLP-RAP assay can detect RR-TB infection with high sensitivity and specificity, indicating that this assay has the prospect of being applied for rapid and sensitive RR-TB detection in general laboratories where fluorescent qPCR instrument is available.

Drug resistance profile of Mycobacterium kansasii clinical isolates before and after 2-month empirical antimycobacterial treatment

OBJECTIVES

Mycobacterium kansasii pulmonary disease is frequently misdiagnosed and treated as tuberculosis, especially in countries with high tuberculosis burden. This study aimed to investigate the drug resistance profile of M.kansasii in patients with M.kansasii pulmonary disease in Shanghai and to determine the variations in drug resistance after 2 months of antimycobacterial treatment.

METHODS

All patients with a diagnosis of M.kansasii pulmonary disease from 2017 to 2019 in Shanghai were retrospectively analysed. Whole-genome sequencing was performed, and the minimum inhibitory concentration (MIC) to antimycobacterial drugs was measured using the broth microdilution method.

RESULTS

In total, 191 patients had a diagnosis of M.kansasii pulmonary disease. Of them, 24.1% (46/191) had persistent positive culture after 2 months of antimycobacterial treatment. Whole-genome sequencing revealed that the 46 paired isolates had a difference of <17 single nucleotide polymorphisms, thus excluding the possibility of exogenous reinfection. More than 90% of the baseline isolates were sensitive to rifampin, clarithromycin, moxifloxacin, or amikacin, whereas a high resistance to ethambutol (118/191, 61.8%) and 4 μg/mL of isoniazid (32/191, 16.8%) were observed. Two isolates presented high resistance to rifamycin (i.e. a rifampin MIC of >8 μg/mL and a rifabutin MIC of 8 μg/mL) both containing the rpoB mutation (S454L). The increase of MIC to rifampin, ethambutol, and/or isoniazid was identified in 50.0% (23/46) of the patients.

DISCUSSION

A high prevalence of innate resistance to ethambutol and isoniazid was observed among circulating M.kansasii clinical strains in Shanghai. The increase in drug resistance under empirical antimycobacterial treatment highlighted the urgency of definitive species identification before initiating treatment.

Whole-genome sequencing to characterize the genetic structure and transmission risk of Mycobacterium tuberculosis in Yichang city of China

Objective

The burden of both general and drug-resistant tuberculosis in rural areas is higher than that in urban areas in China. To characterize the genetic structure and transmission risk of Mycobacterium tuberculosis in rural China, we used whole genome sequencing to analyze clinical strains collected from patients in two counties of Yichang for three consecutive years.

Methods

From 2018 to 2020, sputum samples were collected for cultures from patients with suspected tuberculosis in Yidu and Zigui county, and DNA was extracted from the positive strains for genome sequencing. The online SAM-TB platform was used to identify the genotypes and drug resistance-related mutations of each strain, establish a phylogenetic tree, and calculated the genetic distances between pairwise strains. Twelve single nucleotide polymorphisms (SNPs) were used as thresholds to identify transmission clusters. The risk of related factors was estimated by univariable and multivariable logistic regression.

Results

A total of 161 out of the collected 231 positive strains were enrolled for analysis, excluding non-tuberculous mycobacterium and duplicate strains from the same patient. These strains belonged to Lineage 2 (92, 57.1%) and Lineage 4 (69, 42.9%), respectively. A total of 49 (30.4%) strains were detected with known drug resistance-related mutations, including 6 (3.7%) multidrug-resistant-TB (MDR-TB) strains and 11 (6.8%) RIF-resistant INH-susceptible TB (Rr-TB) strains. Six of the MDR/Rr-TB (35.3%) were also resistant to fluoroquinolones, which made them pre-extensively drug-resistant TB (pre-XDR-TB). There were another seven strains with mono-resistance to fluoroquinolones and one strain with resistance to both INH and fluoroquinolones, making the overall rate of fluoroquinolones resistance 8.7% (14/161). A total of 50 strains (31.1%) were identified as transmission clusters. Patients under 45 years old (adjusted odds ratio 3.46 [95% confidential intervals 1.28-9.35]), treatment-naive patients (6.14 [1.39-27.07]) and patients infected by lineage 4 strains (2.22 [1.00-4.91]) had a higher risk of transmission.

Conclusion

The drug resistance of tuberculosis in rural China, especially to the second-line drug fluoroquinolones, is relatively serious. The standardized treatment for patients and the clinical use of fluoroquinolones warrant attention. At the same time, the recent transmission risk of tuberculosis is high, and rapid diagnosis and treatment management at the primary care needs to be strengthened.

Evaluation Study of xMAP TIER Assay on a Microsphere-Based Platform for Detecting First-Line Anti-Tuberculosis Drug Resistance

Early diagnosis of drug susceptibility for tuberculosis (TB) patients could guide the timely initiation of effective treatment. We evaluated a novel multiplex xMAP TIER (Tuberculosis-Isoniazid-Ethambutol-Rifampicin) assay based on the Luminex xMAP system to detect first-line anti-tuberculous drug resistance. Deoxyribonucleic acid samples from 353 Mycobacterium tuberculosis clinical isolates were amplified by multiplex polymerase chain reaction, followed by hybridization and analysis through the xMAP system. Compared with the broth microdilution method, the sensitivity and specificity of the xMAP TIER assay for detecting resistance was 94.9% (95%CI, 90.0-99.8%) and 98.9% (95%CI, 97.7-100.0%) for rifampicin; 89.1% (95%CI, 83.9-94.3%) and 100.0% (95%CI, 100.0-100.0%) for isoniazid; 82.1% (95% CI, 68.0-96.3%) and 99.7% (95% CI, 99.0-100.0%) for ethambutol. With DNA sequencing as the reference standard, the sensitivity and specificity of xMAP TIER for detecting resistance were 95.0% (95% CI, 90.2-99.8%) and 99.6% (95% CI, 98.9-100.0%) for rifampicin; 96.9% (95% CI, 93.8-99.9%) and 100.0% (95% CI, 100.0-100.0%) for isoniazid; 86.1% (95% CI, 74.8-97.4%) and 100.0% (95% CI, 100.0-100.0%) for ethambutol. The results achieved showed that the xMAP TIER assay had good performance for detecting first-line anti-tuberculosis drug resistance, and it has the potential to diagnose drug-resistant tuberculosis more accurately due to the addition of more optimal design primers and probes on open architecture xMAP system.

Rapid Identification of Drug Resistance and Phylogeny in M. tuberculosis, Directly from Sputum Samples

Tuberculosis (TB) remains one of the most important infectious diseases globally. Establishing a resistance profile from the initial TB diagnosis is a priority. Rapid molecular tests evaluate only the most common genetic variants responsible for resistance to certain drugs, and Whole Genome Sequencing (WGS) needs culture prior to next-generation sequencing (NGS), limiting their clinical value. Targeted sequencing (TS) from clinical samples avoids these drawbacks, providing a signature of genetic markers that can be associated with drug resistance and phylogeny. In this study, a proof-of-concept protocol was developed for detecting genomic variants associated with drug resistance and for the phylogenetic classification of Mycobacterium Tuberculosis (Mtb) in sputum samples. Initially, a set of Mtb reference strains from the WHO were sequenced (WGS and TS). The results from the protocol agreed >95% with WHO reported data and phenotypic drug susceptibility testing (pDST). Lineage genetics results were 100% concordant with those derived from WGS. After that, the TS protocol was applied to sputum samples from TB patients to detect resistance to first- and second-line drugs and derive phylogeny. The accuracy was >90% for all evaluated drugs, except Eto/Pto (77.8%), and 100% were phylogenetically classified. The results indicate that the described protocol, which affords the complete drug resistance profile and phylogeny of Mtb from sputum, could be useful in the clinical area, advancing toward more personalized and more effective treatments in the near future. IMPORTANCE The COVID-19 pandemic negatively affected the progress in accessing essential Tuberculosis (TB) services and reducing the burden of TB disease, resulting in a decreased detection of new cases and increased deaths. Generating molecular diagnostic tests with faster results without losing reliability is considered a priority. Specifically, developing an antimicrobial resistance profile from the initial stages of TB diagnosis is essential to ensure appropriate treatment. Currently available rapid molecular tests evaluate only the most common genetic variants responsible for resistance to certain drugs, limiting their clinical value. In this work, targeted sequencing on sputum samples from TB patients was used to identify Mycobacterium tuberculosis mutations in genes associated with drug resistance and to derive a phylogeny of the infecting strain. This protocol constitutes a proof-of-concept toward the goal of helping clinicians select a timely and appropriate treatment by providing them with actionable information beyond current molecular approaches.

Investigating resistance in clinical Mycobacterium tuberculosis complex isolates with genomic and phenotypic antimicrobial susceptibility testing: a multicentre observational study

BACKGROUND

Whole-genome sequencing (WGS) of Mycobacterium tuberculosis complex has become an important tool in diagnosis and management of drug-resistant tuberculosis. However, data correlating resistance genotype with quantitative phenotypic antimicrobial susceptibility testing (AST) are scarce.

METHODS

In a prospective multicentre observational study, 900 clinical M tuberculosis complex isolates were collected from adults with drug-resistant tuberculosis in five high-endemic tuberculosis settings around the world (Georgia, Moldova, Peru, South Africa, and Viet Nam) between Dec 5, 2014, and Dec 12, 2017. Minimum inhibitory concentrations (MICs) and resulting binary phenotypic AST results for up to nine antituberculosis drugs were determined and correlated with resistance-conferring mutations identified by WGS.

FINDINGS

Considering WHO-endorsed critical concentrations as reference, WGS had high accuracy for prediction of resistance to isoniazid (sensitivity 98·8% [95% CI 98·5-99·0]; specificity 96·6% [95% CI 95·2-97·9]), levofloxacin (sensitivity 94·8% [93·3-97·6]; specificity 97·1% [96·7-97·6]), kanamycin (sensitivity 96·1% [95·4-96·8]; specificity 95·0% [94·4-95·7]), amikacin (sensitivity 97·2% [96·4-98·1]; specificity 98·6% [98·3-98·9]), and capreomycin (sensitivity 93·1% [90·0-96·3]; specificity 98·3% [98·0-98·7]). For rifampicin, pyrazinamide, and ethambutol, the specificity of resistance prediction was suboptimal (64·0% [61·0-67·1], 83·8% [81·0-86·5], and 40·1% [37·4-42·9], respectively). Specificity for rifampicin increased to 83·9% when borderline mutations with MICs overlapping with the critical concentration were excluded. Consequently, we highlighted mutations in M tuberculosis complex isolates that are often falsely identified as susceptible by phenotypic AST, and we identified potential novel resistance-conferring mutations.

INTERPRETATION

The combined analysis of mutations and quantitative phenotypes shows the potential of WGS to produce a refined interpretation of resistance, which is needed for individualised therapy, and eventually could allow differential drug dosing. However, variability of MIC data for some M tuberculosis complex isolates carrying identical mutations also reveals limitations of our understanding of the genotype and phenotype relationships (eg, including epistasis and strain genetic background).

FUNDING

Bill & Melinda Gates Foundation, German Centre for Infection Research, German Research Foundation, Excellence Cluster Precision Medicine of Inflammation (EXC 2167), and Leibniz ScienceCampus EvoLUNG.

A university-clustered tuberculosis outbreak during the COVID-19 pandemic in eastern China

During the COVID-19 pandemic in 2020, a tuberculosis outbreak occurred in a university in eastern China, with 4,488 students and 421 staff on the campus. A 19-year-old student was diagnosed in August 2019. Later, the first round of screening was initiated among close contacts, but no active cases were found. Till September 2020, four rounds of screening were performed. Four rounds of screening were conducted on September 9, November 8, November 22-25 in 2019 and September 2020, with 0, 5, 0 and 43 cases identified, respectively. A total of 66 active tuberculosis were found in the same university, including 4 sputum culture-positive and 7 sputum smear-positive. The total attack rate of active tuberculosis was 1.34% (66/4909). The whole-genome sequencing showed that the isolates belonged to the same L2 sub-specie and were sensitive to all tested antituberculosis drugs. Delay detection, diagnosis and report of cases were the major cause of this university tuberculosis epidemic. More attention should be paid to the asymptomatic students in the index class. After the occurrence of tuberculosis cases in schools, multiple rounds of screening should be carried out, and preventive therapy should be applied in a timely manner.

Use of Whole-Genome Sequencing to Explore Mycobacterium tuberculosis Complex Circulating in a Hotspot Department in France

The Seine-Saint-Denis is the French metropolitan department with the highest incidence of tuberculosis (TB). Our aim was to explore epidemiological and phylogenetic characteristics of TB strains in this hotspot department. We performed WGS on 227 strains of Mycobacterium tuberculosis complex isolated from patients at the Avicenne Hospital from 2016 to 2021 and randomly selected to represent the clinical diversity of French TB localization. Clinical and demographic data were recorded for each TB patient. The mean age of patients was 36 years old. They came from Africa (44%), Asia (27%), Europe (26%) and America (3%). Strains isolated from extrapulmonary samples were associated with Asian patients, whereas strains isolated from pulmonary samples were associated with European patients. We observed a high level of lineage diversity in line with the known worldwide diversity. Interestingly, lineage 3 was associated with lymph node TB. Additionally, the sensitivity of WGS for predicting resistance was 100% for rifampicin, isoniazid and ethambutol and 66.7% for pyrazinamide. The global concordance with drug-susceptibility testing using the phenotypic approach was 97%. In microbiology laboratories, WGS turns out to be an essential tool for better understanding local TB epidemiology, with direct access to circulating lineage identification and to drug susceptibilities to first- and second-line anti-TB drugs.

Comparative genomic analysis of Escherichia coli strains obtained from continuous imipenem stress evolution

The carbapenem-resistant Escherichia coli (E. coli) has aroused increasing attention worldwide, especially in terms of imipenem (IMP) resistance. The molecular mechanism of IMP resistance remains unclear. This study aimed to explore the resistance mechanisms of IMP in E. coli. Susceptible Sx181-0-1 strain was induced into resistance strains by adaptive laboratory evolution. The drug resistance spectrum was measured using the disk diffusion and microbroth dilution methods. Whole-genome sequencing and resequencing were used to analyze the non-synonymous single-nucleotide polymorphisms (nsSNPs) between the primary susceptible strain and resistant strains. The expression levels of these genes with nsSNPs were identified by real-time quantitative PCR (RT-qPCR). Resistance phenotype appeared in the induced 15th generation (induction time = 183 h). Sx181-32 and Sx181-256, which had minimum inhibitory concentrations of IMP of 8 and 64 µg mL-1, were isolated during continuous subculture exposed to increasing concentrations of IMP, respectively. Nineteen nsSNPs were observed both in Sx181-32 and Sx181-256, including rpsU, sdaC, zwf, ttuC, araJ, dacC, mrdA, secF, dacD, lpxD, mrcB, ftsI, envZ, and two unknown function genes (orf01892 and orf01933). Among these 15 genes, five genes (dacC, mrdA, lpxD, mrcB, and ftsI) were mainly involved in cell wall synthesis. The mrdA (V338A, L378P, and M574I) and mrcB (P784L, A736V, and T708A) had three amino acid substitutions, respectively. The expression levels of rpsU, ttuC and orf01933 were elevated in both Sx181-32 and Sx181-256 compared to Sx181-0-1. The expression levels of these genes were elevated in Sx181-256, except for araJ. Bacteria developed resistance to antimicrobials by regulating various biological processes, among which the most involved is the cell wall synthesis (dacC, mrdA, lpxD, mrcB, and ftsI). The combination mutations of mrdA, envZ, and ftsI genes may increase the resistance to IMP. Our study could improve the understanding of the molecular mechanism underlying the IMP resistance of E. coli.