The 2021 WHO catalogue of Mycobacterium tuberculosis complex mutations associated with drug resistance: A genotypic analysis

The epidemiology and gene mutation characteristics of pyrazinamide-resistant Mycobacterium tuberculosis clinical isolates in Southern China

This study investigates the epidemic trend of pyrazinamide (PZA)-resistant tuberculosis in Southern China over 11 years (2012-2022) and evaluates the mutation characteristics of PZA resistance-related genes (pncA, rpsA, and panD) in clinical Mycobacterium tuberculosis (M. tuberculosis) isolates. To fulfil these goals, we analyzed the phenotypic PZA resistance characteristics of 14,927 clinical isolates for which Bactec MGIT 960 PZA drug susceptibility testing (DST) results were available, revealing that 2,054 (13.76%) isolates were resistant to PZA. After evaluating the annual variation in the PZA resistance rate among tuberculosis cases in this region, it was observed that it decreased from 37.21% to 6.45% throughout the initial 7 years (2012-2018) and then increased from 8.01% to 12.12% over the subsequent 4 years (2019-2022). Sequences of pncA were obtained from 402 clinical M. tuberculosis complex isolates. For rpsA and panD, sequences were obtained from 360 clinical M. tuberculosis complex isolates. Mutations in pncA were found in 8 out of 223 PZA-sensitive isolates (3.59%) and 105 of 179 (58.66%) PZA-resistant isolates. Conversely, non-synonymous mutations in rpsA were identified in 5 of 137 (3.65%) PZA-resistant isolates, whereas the mutation ratio of rpsA among PZA-sensitive isolates was high at 14.03% (31/221). This difference in the rpsA mutation rate was statistically significant (P = 0.001, chi-square test). No panD mutations were observed in the 137 PZA-resistant isolates, whereas two PZA-sensitive isolates harboured point mutations in panD, including one nonsense mutation (C433 T) and another C-69 T mutation. These findings indicate that rpsA and panD may not significantly contribute to the development of PZA resistance in clinical M. tuberculosis isolates.

Performance of a molecular beacon-based qPCR method for detection of fluoroquinolone resistance in Mycobacterium tuberculosis: A study confirmed by sequencing

Multidrug-resistant tuberculosis (MDR-TB) poses a serious threat to the control and treatment of tuberculosis (TB). Rapid diagnosis of resistant strains via utilization of molecular techniques is of critical importance on the proper management of the patients. The objective of this study was to develop a quantitative polymerase chain reaction (qPCR) method for the detection of mutation-based fluoroquinolone (FQ) resistance in Mycobacterium tuberculosis isolates. Primers and a molecular-beacon probe were designed to target quinolone-resistance-determining-region (QRDR) of the gyrA gene of M. tuberculosis. Amplification conditions and concentrations of primers/probe were optimized, and the effectiveness of the optimized qPCR method was tested on 50 MDR M. tuberculosis strains. To confirm the qPCR results, all strains were also screened for mutations in the gyrA gene using Sanger sequencing. The optimized qPCR method had analytical sensitivity of 96.5 cfu/ml. The method detected FQ resistance in 7 (14 %) of the 50 MDR-strains via either no or significantly decreased fluorescence signal due to mutations associated with FQ resistance. The sequencing of these seven strains detected three resistance-associated mutations (A90V, D94A and D94G). Of the 43 FQ-susceptible strains, 10 strains with wild-type gene sequences yielded strong fluorescent signals above 450 RFU, while the remaining 33 strains harboring a non-resistance-associated mutation (S95T) showed decreased fluorescence signals <350 RFU. The sensitivity and specificity of the qPCR method for detection of the mutations related to resistance was ≥99.9 % and 98 %, respectively. Consequently, the utility of the optimized qPCR method for the identification of mutation-based FQ resistance is promising.

Diagnostic yield of nine user-friendly bioinformatics tools for predicting Mycobacterium tuberculosis drug resistance: A systematic review and network meta-analysis

To compare the diagnostic yield of various bioinformatics tools for predicting Mycobacterium tuberculosis drug resistance. A systematic review of PubMed, Embase, Scopus, Web of Science, CINAHL and the Cochrane Library was performed to identify studies reporting the effectiveness of bioinformatic tools for predicting resistance to anti-tuberculosis (TB) drugs. Data were collected and pooled using random-effects meta-analysis and Bayesian network meta-analysis (NMA). Summary receiver operating characteristic curves (SROCs) analysis were performed, and superiority index (SI) and area under the curve (AUC) were calculated. Thirty-three studies evaluated 9 different bioinformatics tools for predicting resistance to 14 anti-TB drugs. NMA and SROCs demonstrated that TBProfiler, TGS-TB, Mykrobe, PhyResSE, and SAM-TB all exhibited satisfactory performance. Remarkably, TBProfiler stood out with its exceptional ability to predict resistance to the majority of anti-TB drugs, including isoniazid (SI: 3.39 [95% confidence interval (CI): 0.20, 11.00]; AUC: 0.97 [0.95, 0.98]), rifampicin (SI: 6.38 [0.60, 15.00]; AUC: 0.99 [0.98, 1.00]), ethambutol (SI: 5.15 [0.60, 13.00]; AUC: 0.96 [0.94, 0.97]), streptomycin (SI: 3.67 [0.60, 11.00]; AUC: 0.97 [0.95, 0.98], amikacin (SI: 2.49 [0.14, 11.00]; AUC: 0.97 [0.96, 0.99]), kanamycin (SI: 2.26 [0.14, 9.00]; AUC: 0.98 [0.97, 0.99]), levofloxacin (SI: 1.87 [0.11, 9.00]; AUC: 0.95 [0.93, 0.97]), and prothionamide (SI: 2.73 [0.20, 7.00]; AUC: 0.87 [0.84, 0.90]). Meanwhile, Mykrobe demonstrated superior accuracy specifically for moxifloxacin (SI: 3.96 [0.11, 13.00]; AUC: 0.97 [0.95, 0.98]). Lastly, TGS-TB had the best efficacy in predicting resistance to pyrazinamide (SI: 12.53 [1.67, 17.00]; AUC: 0.97 [0.95, 0.98]), capreomycin (SI: 4.22 [0.08, 15.00]; AUC: 1.00 [0.98, 1.00]), and ethionamide (SI: 2.15 [0.33, 7.00]; AUC: 0.96 [0.94, 0.98]). TBProfiler, TGS-TB, Mykrobe, PhyResSE and SAM-TB have all demonstrated outstanding accuracy in predicting resistance to anti-TB drugs. In particular, TBProfiler stood out for its exceptional performance in predicting resistance to most anti-TB drugs, while TGS-TB excelled in predicting resistance to pyrazinamide and certain second-line drugs. The efficacy of SAM-TB requires further investigation to fully establish its reliability and effectiveness. To ensure the accuracy and reliability of genotypic drug susceptibility testing, bioinformatics tools should be refined and adapted continuously to accommodate novel and current resistance-associated mutations.

Development of a Multiplex Real-Time PCR for Diagnosis of Tuberculosis and Multidrug Resistance

The aim of this study was to develop a multiplex qPCR method for diagnosis of tuberculosis and multidrug resistance. The method was constructed with two multiplex qPCR mixes. Mycobacterium tuberculosis and rifampicin (RIF) resistance were assessed in the first PCR mix and isoniazid (INH) resistance in the second PCR mix. Firstly, PCR amplification conditions and concentration of primers and probes were optimized. Then, analytical sensitivity/limit of detection (LOD), analytical specificity, repeatability, accuracy, and effectiveness on clinical samples were analyzed. The LOD value was determined as 124 cfu/mL. In studies conducted on 273 clinical samples, RIF and INH resistance was detected with ≥ 99% sensitivity and specificity. No false positive or negative results were obtained in the accuracy studies. In intra-experiment, inter-experiment, and inter-lot repeatability studies, the coefficient of variation was calculated as between 0.36 and 5.3%. It was also determined that the primers/probes used in this assay did not cross-react with microorganisms other than M. tuberculosis complex. In conclusion, the method optimized in the current study has high performance characteristics indicating that it can be used as an alternative for currently available molecular methods for rapid and accurate diagnosis of pulmonary tuberculosis and multidrug resistance without needing any specific equipment. Further study with different clinical samples will be useful to provide more data regarding routine utility of this method.

Advantages of updated WHO mutation catalog combined with existing whole-genome sequencing-based approaches for Mycobacterium tuberculosis resistance prediction

BACKGROUND

The WHO recently released a second edition of the mutation catalog for predicting drug resistance in Mycobacterium tuberculosis (MTB). This study evaluated its effectiveness compared to existing whole-genome sequencing (WGS)-based prediction methods and proposes a novel approach for its optimization.

METHODS

We tested the accuracy of five tools-the WHO catalog, TB Profiler, SAM-TB, GenTB, and MD-CNN-for predicting drug susceptibility on a global dataset of 36,385 MTB isolates with high-quality phenotypic drug susceptibility testing (DST) and WGS data. By integrating the genotypic DST predictions of these five tools in an ensemble machine learning framework, we developed an improved computational model for MTB drug susceptibility prediction. We then validated the ensemble model on 860 MTB isolates with phenotypic and WGS data collected in Shenzhen, China (2013-2019) and Valencia, Spain (2014-2016).

RESULTS

Among the five genotypic DST tools for predicting susceptibility to ten drugs, MD-CNN exhibited the highest overall performance (AUC 92.1%; 95% CI 89.8-94.4%). The WHO catalog demonstrated the highest specificity of 97.3% (95% CI 95.8-98.4%), while TB Profiler had the best sensitivity at 79.5% (95% CI 71.8-86.2%). The ensemble machine learning model (AUC 93.4%; 95% CI 91.4-95.4%) outperformed all of the five individual tools, with a specificity of 95.4% (95% CI 93.0-97.6%) and a sensitivity of 84.1% (95% CI 78.8-88.8%), principally due to considerable improvements in second-line drug resistance predictions (AUC 91.8%; 95% CI 89.6-94.0%).

CONCLUSIONS

The second edition of the WHO MTB mutation catalog does not, by itself, perform better than existing tools for predicting MTB drug resistance. An integrative approach combining the WHO catalog with other genotypic DST methods significantly enhances prediction accuracy.

Multi-drug resistance and compensatory mutations in Mycobacterium tuberculosis in Vietnam

BACKGROUND

Vietnam is a hotspot for the emergence and spread of multidrug-resistant Mycobacterium tuberculosis. This study aimed to perform a retrospective study on the compensatory evolution in multidrug-resistant M. tuberculosis strains and the association with drug-resistant mutations and M. tuberculosis genotypes.

METHODS

Hundred and seventy-three strains resistant to rifampicin (n = 126) and/or isoniazid (n = 170) (multidrug-resistant = 123) were selected according to different drug-resistant patterns and genotypes. The genes/promoter regions including rpoA, rpoB, rpoC, katG, inhA, inhA promoter, ahpC, ahpC promoter, gyrA, gyrB, and rrs were sequenced for each strain.

RESULTS

Frequency of rifampicin- and isoniazid-resistant mutations in multidrug-resistant strains was 99.2% and 97.0%, respectively. Mutations associated with low -high levels of drug resistance with low- or no-fitness costs compared to the wild type, including rpoB_Ser450Leu, katG_Ser315Thr, inhA-15(A-T), gyrA_Asp94Gly, and rrs_A1401GA, accounted for 46.3%, 76.4%, 16.2%, 8.9%, and 11.4%, respectively, in the multidrug-resistant strains. Beijing and Euro-American genotype strains were associated with high-level drug-resistant mutations, rpoB_Ser450Leu, katG_Ser315Thr, and gyrA_Asp94Gly, while East African-Indian genotype strains were associated with low to high-level drug-resistant mutations, rpoB_His445Asp, rpoB_His445Tyr, inhA-15(C-T) and rrs_A1401G. Multidrug-resistant strains (19.5%) harboured compensatory mutations linked to rifampicin resistance in rpoA, rpoB, or rpoC. Notably, the frequency of compensatory mutations in Beijing genotypes was significantly higher than in East African-Indian genotypes (21.1% vs. 3.3%, OR = 7.7; 95% CI = 1.0 to 61.2, p = 0.03). The proportion of multidrug-resistant strains with rpoB_Ser450Leu mutations carrying rpoA-rpoC mutations was higher than that of strains with other rpoB mutations (OR = 5.4; 95% CI = 1.4 to 21.1, p = 0.02) and was associated with Beijing strains. Only 1.2% (2/170) isoniazid-resistant strains carried aphC-52(C-T) mutation in the promoter region of the ahpC gene, which was hypothesised to be the compensatory mutation in isoniazid-resistant strains. Meanwhile, 11 isoniazid-resistant strains carried a katG mutation combined with either inhA-8(T-C) or inhA-15(A-T) mutations and were associated with East African-Indian strains.

CONCLUSIONS

Mutations associated with high levels of drug resistance without/with low fitness costs (rpoB_Ser450Leu and katG_Ser315Thr) along with compensatory mutations linked to rifampicin resistance were strongly associated with multidrug-resistant M. tuberculosis Beijing strains in Vietnam.

Machine learning-based approach for identification of new resistance associated mutations from whole genome sequences of Mycobacterium tuberculosis

Motivation

Currently available methods for the prediction of genotypic drug resistance in Mycobacterium tuberculosis utilize information on known markers of drug resistance. Hence, machine learning approaches are needed that can discover new resistance markers.

Results

Whole genome sequences with known phenotypic drug resistance profiles have been utilized to train XGBoost and ANN classifiers for 5 first-line and 8 second-line tuberculosis drugs. Benchmarking on a completely independent dataset from CRyPTIC database revealed that our method has high sensitivity (90%-95%) and specificity (94%-99%) for five first-line drugs and robust performance for six second-line drugs with a sensitivity of 77%-89% at over 95% specificity. An explainable AI method, SHapley Additive exPlanations, has successfully identified resistance mutations for each drug in a completely automated way. This approach could not only identify known resistance associated mutations in agreement with the WHO mutation catalogue, but also predicted >100 other potential resistance associated mutations for 13 antibiotics in new genes outside the known resistance loci. Identification of new resistance markers opens up the opportunity for the discovery of novel mechanisms of drug resistance.

Availability and implementation

Our prediction method has been implemented as TB-AMRpred webserver and command line tool, available freely at http://www.nii.ac.in/TB-AMRpred.html and https://github.com/Ankitapal1995/TB-AMRprd.

Risk factors for rifampicin-susceptible and isoniazid-resistant tuberculosis in adult patients with type 2 diabetes mellitus in Nanjing

OBJECTIVE

Globally, Tuberculosis(TB) with type 2 diabetes mellitus (T2DM) is becoming increasingly serious, especially the emergence of rifampicin-susceptible and isoniazid-resistant tuberculosis (Hr-TB), which increases the difficulty of treatment and the burden of disease. Therefore, this single-center retrospective cohort study analyzed risk factors of Hr-TB in adult patients with T2DM and pulmonary tuberculosis (PTB) in Nanjing to guide clinical practice and improve the long-term prognosis of patients.

METHODS

The clinical data of 279 adult inpatients diagnosed with culture-positive PTB and T2DM in the Second Hospital of Nanjing from January 2019 and December 2021 were collected. According to the drug susceptibility testing (DST) results, 44 patients with Hr-TB were categorized as the Hr-TB group, while the remaining 235 patients with drug-susceptible tuberculosis (DS-TB) were classified as DS-TB group. Hierarchical logistic regression was employed for multivariate analysis to identify variables associated with Hr-TB in patients with T2DM.

RESULTS

There were no significant differences in age, sex, body mass index (BMI), smoking, drinking, ethnicity, education level, or comorbidities between the DS-TB and Hr-TB groups. Multivariate logistic regression analysis revealed that, history of previous tuberculosis treatment (OR = 2.348, 95%CI: 1.025 ~ 5.379, P = 0.044), poor FPG control (OR = 2.402, 95%CI: 1.208 ~ 4.776, P = 0.012), and serum iron levels ≥ 14.3µmol/l (OR = 2.808, 95%CI: 1.334 ~ 5.910, P = 0.007) are independent risk factors for Hr-TB in adult patients with T2DM in Nanjing. Within the cohort, 241 patients were Newly treatment tuberculosis patients, and among them, poor FPG control (OR = 2.296, 95%CI: 1.073 ~ 4.915, P = 0.032), and serum iron levels ≥ 14.3µmol/l (OR = 2.418, 95%CI: 1.048 ~ 5.577, P = 0.038) were identified as risk factors for Hr-TB.

CONCLUSION

Poor fasting glycemic control and serum iron levels ≥ 14.3µmol/L are independent risk factors for the development of Hr-TB in adults with T2DM and PTB, moreover, the contribution of these as risk factors were more pronounced in the newly treatment tuberculosis patients subgroup than patients with a history of previous tuberculosis treatment. History of previous tuberculosis treatment was also found to be a risk factor for Hr-TB in adults with T2DM.

Multivariable regression models improve accuracy and sensitive grading of antibiotic resistance mutations in Mycobacterium tuberculosis

Rapid genotype-based drug susceptibility testing for the Mycobacterium tuberculosis complex (MTBC) relies on a comprehensive knowledgebase of the genetic determinants of resistance. Here we present a catalogue of resistance-associated mutations using a regression-based approach and benchmark it against the 2nd edition of the World Health Organisation (WHO) mutation catalogue. We train multivariate logistic regression models on over 52,000 MTBC isolates to associate binary resistance phenotypes for 15 antitubercular drugs with variants extracted from candidate resistance genes. Regression detects 450/457 (98%) resistance-associated variants identified using the existing method (a.k.a, SOLO method) and grades 221 (29%) more total variants than SOLO. The regression-based catalogue achieves higher sensitivity on average (+3.2 percentage points, pp) than SOLO with smaller average decreases in specificity (-1.0 pp) and positive predictive value (-1.6 pp). Sensitivity gains are highest for ethambutol, clofazimine, streptomycin, and ethionamide as regression graded considerably more resistance-associated variants than SOLO for these drugs. There is no difference between SOLO and regression with regards to meeting the target product profiles set by the WHO for genetic drug susceptibility testing, except for rifampicin, for which regression specificity is below the threshold of 98% at 97%. The regression pipeline also detects isoniazid resistance compensatory mutations in ahpC and variants linked to bedaquiline and aminoglycoside hypersusceptibility. These results inform the continued development of targeted next generation sequencing, whole genome sequencing, and other commercial molecular assays for diagnosing resistance in the MTBC.

TBtypeR: Sensitive detection and sublineage classification of Mycobacterium tuberculosis complex mixed-strain infections

Tuberculosis (TB) is typically attributed to a single infecting strain of the Mycobacterium tuberculosis Complex (MTBC), however mixed-strain infections are more common than reported due to the limitations of conventional diagnostics. While whole genome sequencing (WGS) methods have improved the detection of mixed-strain infections, existing tools struggle to reliably identify mixed-strain infections with frequencies below 10%. TBtypeR, a new tool, addresses this challenge by comparing WGS data to a phylogenetic SNP panel of over 10,000 sites and 164 MTBC phylotypes and using a model based on the binomial distribution to classify sublineage mixtures at frequencies as low as 1%. Extensive benchmarking shows TBtypeR outperforms current methods. Application to a published dataset of 5000 WGS samples identified 305 mixed-strain infections, six-fold higher than previously reported. The TBtypeR R package and a Nextflow pipeline are available at github.com/bahlolab/TBtypeR, providing a powerful tool for studying TB epidemiology and mixed-strain infections.

Electroencephalographic differences between waking and sleeping periods in patients with prolonged disorders of consciousness at different levels of consciousness

Objective

This study aimed to explore differences in sleep electroencephalogram (EEG) patterns in individuals with prolonged disorders of consciousness, utilizing polysomnography (PSG) to assist in distinguishing between the vegetative state (VS)/unresponsive wakefulness syndrome (UWS) and the minimally conscious state (MCS), thereby reducing misdiagnosis rates and enhancing the quality of medical treatment.

Methods

A total of 40 patients with prolonged disorders of consciousness (pDOC; 27 patients in the VS/UWS and 13 in the MCS) underwent polysomnography. We analyzed differential EEG indices between VS/UWS and MCS groups and performed correlation analyses between these indices and the Coma Recovery Scale-Revised (CRS-R) scores. The diagnostic accuracy of the differential indices was evaluated using receiver operating characteristic (ROC) curves.

Results

1. The fractal dimension (Higuchi's fractal dimension (HFD)) of patients in the MCS tended to be higher than that of patients in the VS/UWS across all phases, with a significant difference only in the waking phase (p < 0.05). The HFD in the waking phase was positively correlated with the CRS-R score and exhibited the highest diagnostic accuracy at 88.3%. The Teager-Kaiser energy operator (TKEO) also showed higher levels in patients in the MCS compared to those in the VS/UWS, significantly so in the NREM2 phase (p < 0.05), with a positive correlation with the CRS-R score and diagnostic accuracy of 75.2%. The δ-band power spectral density [PSD(δ)] in the patients in the MCS was lower than that in those in the VS/UWS, significantly so in the waking phase (p < 0.05), and it was negatively correlated with the CRS-R score, with diagnostic accuracy of 71.5%.

Conclusion

Polysomnography for the VS/UWS and MCS revealed significant differences, aiding in distinguishing between the two patient categories and reducing misdiagnosis rates. Notably, the HFD and PSD(δ) showed significantly better performance during wakefulness compared to sleep, while the TKEO was more prominent in the NREM2 stage. Notably, the HFD exhibited a robust correlation with the CRS-R scores, the highest diagnostic accuracy, and immense promise in the clinical diagnosis of prolonged disorders of consciousness.

Tiled Amplicon Sequencing Enables Culture-free Whole-Genome Sequencing of Pathogenic Bacteria From Clinical Specimens

Pathogen sequencing is an important tool for disease surveillance and demonstrated its high value during the COVID-19 pandemic. Viral sequencing during the pandemic allowed us to track disease spread, quickly identify new variants, and guide the development of vaccines. Tiled amplicon sequencing, in which a panel of primers is used for multiplex amplification of fragments across an entire genome, was the cornerstone of SARS-CoV-2 sequencing. The speed, reliability, and cost-effectiveness of this method led to its implementation in academic and public health laboratories across the world and adaptation to a broad range of viral pathogens. However, similar methods are not available for larger bacterial genomes, for which whole-genome sequencing typically requires in vitro culture. This increases costs, error rates and turnaround times. The need to culture poses particular problems for medically important bacteria such as Mycobacterium tuberculosis, which are slow to grow and challenging to culture. As a proof of concept, we developed two novel whole-genome amplicon panels for M. tuberculosis and Streptococcus pneumoniae. Applying our amplicon panels to clinical samples, we show the ability to classify pathogen subgroups and to reliably identify markers of drug resistance without culturing. Development of this work in clinical settings has the potential to dramatically reduce the time of diagnosis of drug resistance for multiple drugs in parallel, enabling earlier intervention for high priority pathogens.

Analysis of genetic characteristics associated with reduced bedaquiline susceptibility in multidrug-resistant Mycobacterium tuberculosis

Bedaquiline (BDQ) has shown efficacy in shortening treatment duration and enhancing treatment success rates for multidrug-resistant tuberculosis (MDR-TB), thereby prompting widespread adoption. However, resistance to BDQ has emerged. This study aimed to identify genetic characteristics associated with decreased susceptibility to BDQ, using a public database to aid in the detection of resistant strains. Seventy-one BDQ-resistant and 929 BDQ-susceptible isolates from the open-source CRyPTIC database were selected for analysis. Variant calling was conducted via the clockwork pipeline. Univariate logistic regression was performed for each gene mutation, followed by LASSO regression for further variant selection. Ultimately, a multiple linear regression model was developed using log2-transformed Minimum Inhibitory Concentration values as the dependent variable, with variant selection refined through stepwise regression based on the Akaike Information Criterion. Ten gene mutations were significantly associated with reduced BDQ susceptibility, including two key gene mutations: Rv0678_141_ins_1 and Rv1979c_D249E, with effect estimates of 1.76 (95 % CI: 0.67-2.84) and 1.69 (95 % CI: 0.22-3.17), respectively. Other implicated genes included Rv2699c_-84_del_1, hsaB_I179T, mmpL9_T241A, pncA_C14R, Rv0373c_G621S, Rv0893c_L27F, Rv1770_A4D, and Rv3428c_S327C. This study identified ten gene mutations linked to decreased susceptibility to BDQ, providing a reference for developing a comprehensive catalog of BDQ-resistant genes.

Association between toxin-antitoxin system mutations and global transmission of MDR-TB

BACKGROUND

The emergence of Multidrug-Resistant Tuberculosis (MDR-TB) poses a significant threat to global tuberculosis control efforts. This study aimed to examine the influence of mutations in Toxin-Antitoxin system genes on the global transmission of MDR-TB caused by Mycobacterium tuberculosis (M. tuberculosis).

METHODS

Whole-genome sequencing was conducted on 13,518 M. tuberculosis isolates. Genes of the Toxin-Antitoxin system were obtained from the National Center for Biotechnology Information (NCBI) Gene database. Techniques such as Random Forest, Gradient Boosting Decision Tree, and Generalized Linear Mixed Models were employed to identify mutation sites in Toxin-Antitoxin system-related genes that facilitated the transmission of MDR-TB.

RESULTS

4,066 (30.08%) were identified as MDR-TB strains of all analyzed isolates. We found significant associations between specific gene mutations and MDR-TB transmission clusters including mutations in Rv0298 (G213A), Rv1959c (parE1, C88T), Rv1960c (parD1, C134T), Rv1991A (maze, G156A), Rv2547 (vapB, C54G), Rv2862A (vapB23, T2C), and Rv3385c (vapB46, G70A). Additionally, several gene mutations associated with MDR-TB transmission clades such as Rv1956 (higA, G445T), Rv1960c (parD1, C134T), and Rv1962A (vapB35, G99A) were noted. Certain gene mutations including vapB35 (G99A), higA (G445T), and parD1 (C134T) correlated with cross-regional transmission clades.

CONCLUSION

This study highlights the significant association between specific gene mutations in the Toxin-Antitoxin system and the global transmission of MDR-TB, providing valuable insights for developing targeted interventions to control MDR-TB.

The catalogue of Mycobacterium tuberculosis mutations associated with drug resistance to 12 drugs in China from a nationwide survey: a genomic analysis

BACKGROUND

WHO issued the first edition catalogue of Mycobacterium tuberculosis complex (MTBC) mutations associated with drug resistance in 2021. However, country-specific issues might lead to arising complex and additional drug-resistant mutations. We aimed to fully reflect the characteristics of drug resistance mutations in China.

METHODS

We analysed MTBC isolates from the nationwide drug-resistant tuberculosis surveillance with 70 counties in 31 provinces, municipalities, and autonomous regions in China. Three types of MYCOTB plates were used to perform drug susceptibility testing for 12 antibiotics (rifampicin, isoniazid, ethambutol, levofloxacin, moxifloxacin, amikacin, kanamycin, ethionamide, clofazimine, linezolid, delamanid, and bedaquiline). Mutations were divided into five groups according to their odds ratios, positive predictive values, false discovery rate-corrected p values, and 95% CIs: (1) associated with resistance; (2) associated with resistance-interim; (3) uncertain significance; (4) not associated with resistance-interim; and (5) not associated with resistance. The Wilcoxon rank-sum and Kruskal-Wallis tests were used to quantify the association between mutations and minimum inhibitory concentrations (MICs). Our dataset was compared with the first edition of the WHO catalogue.

FINDINGS

We analysed 10 146 MTBC isolates, of which 9071 (89·4%) isolates were included in the final analysis. 744 (8·2%) isolates were resistant to rifampicin and 1339 (14·8%) to isoniazid. 208 (1·9%) of 11 065 mutations were classified as associated with resistance or associated with resistance-interim. 33 (97·1%) of 34 mutations in group 1 and 92 (52·9%) of 174 in group 2 also appeared in groups 1 or 2 of the WHO catalogue. Of 81 indel mutations in group 2, 15 (18·5%) were in the WHO catalogue. The newly discovered mutation gyrA_Ala288Asp was associated with levofloxacin resistance. MIC values for rifampicin, isoniazid, moxifloxacin, and levofloxacin corresponding to resistance mutations in group 1 were significantly different (p<0·0001), and 12 high-level resistance mutations were detected. 61 mutations in group 3 occurred as solo in at least five phenotypically susceptible isolates, but with MIC values moderately higher than other susceptible isolates. Among 945 phenotypically resistant but genotypically susceptible isolates, 433 (45·8%) were mutated for at least one efflux pump gene.

INTERPRETATION

Our analysis reflects the complexity of drug resistance mutations in China and suggests that indel mutations, efflux pump genes, protein structure, and MICs should be fully considered in the WHO catalogue, especially in countries with a high tuberculosis burden.

FUNDING

National Key Research and Development Program of China and the Science and Technology Major Project of Tibetan Autonomous Region of China.

Exploring uncatalogued genetic variation in antimicrobial resistance gene families in Escherichia coli: an observational analysis

BACKGROUND

Antimicrobial resistance (AMR) in Escherichia coli is a global problem associated with substantial morbidity and mortality. AMR-associated genes are typically annotated based on similarity to variants in a curated reference database, with the implicit assumption that uncatalogued genetic variation within these is phenotypically unimportant. In this study, we evaluated the performance of the AMRFinder tool and, subsequently, the potential for discovering new AMR-associated gene families and characterising variation within existing ones to improve genotype-to-susceptibility phenotype predictions in E coli.

METHODS

In this cross-sectional study of international genome sequence data, we assembled a global dataset of 9001 E coli sequences from five publicly available data collections predominantly deriving from human bloodstream infections from: Norway, Oxfordshire (UK), Thailand, the UK, and Sweden. 8555 of these sequences had linked antibiotic susceptibility data. Raw reads were assembled using Shovill and AMR genes (relevant to amoxicillin-clavulanic acid, ampicillin, ceftriaxone, ciprofloxacin, gentamicin, piperacillin-tazobactam, and trimethoprim) extracted using the National Center for Biotechnology Information AMRFinder tool (using both default and strict [100%] coverage and identity filters). We assessed the predictive value of the presence of these genes for predicting resistance or susceptibility against US Food and Drug Administration thresholds for major and very major errors. Mash was used to calculate the similarity between extracted genes using Jaccard distances. We empirically reclustered extracted gene sequences into AMR-associated gene families (≥70% match) and antibiotic-resistance genes (ARGs; 100% match) and categorised these according to their frequency in the dataset. Accumulation curves were simulated and correlations between gene frequency in the Oxfordshire and other datasets calculated using the Spearman coefficient. Firth regression was used to model the association between the presence of blaTEM-1 variants and amoxicillin-clavulanic acid or piperacillin-tazobactam resistance, adjusted for the presence of other relevant ARGs.

FINDINGS

The performance of the AMRFinder database for genotype-to-phenotype predictions using strict 100% identity and coverage thresholds did not meet US Food and Drug Administration thresholds for any of the seven antibiotics evaluated. Relaxing filters to default settings improved sensitivity with a specificity cost. For all antibiotics, most explainable resistance was associated with the presence of a small number of genes. There was a proportion of resistance that could not be explained by known ARGs; this ranged from 75·1% for amoxicillin-clavulanic acid to 3·4% for ciprofloxacin. Only 18 199 (51·5%) of the 35 343 ARGs detected had a 100% identity and coverage match in the AMRFinder database. After empirically reclassifying genes at 100% nucleotide sequence identity, we identified 1042 unique ARGs, of which 126 (12·1%) were present ten times or more, 313 (30·0%) were present between two and nine times, and 603 (57·9%) were present only once. Simulated accumulation curves revealed that discovery of new (100% match) ARGs present more than once in the dataset plateaued relatively quickly, whereas new singleton ARGs were discovered even after many thousands of isolates had been included. We identified a strong correlation (Spearman coefficient 0·76 [95% CI 0·73-0·80], p<0·0001) between the number of times an ARG was observed in Oxfordshire and the number of times it was seen internationally, with ARGs that were observed six times in Oxfordshire always being found elsewhere. Finally, using the example of blaTEM-1, we showed that uncatalogued variation, including synonymous variation, is associated with potentially important phenotypic differences; for example, two common, uncatalogued blaTEM-1 alleles with only synonymous mutations compared with the known reference were associated with reduced resistance to amoxicillin-clavulanic acid (adjusted odds ratio 0·58 [95% CI 0·35-0·95], p=0·031) and piperacillin-tazobactam (0·50 [95% CI 0·29-0·82], p=0·005).

INTERPRETATION

We highlight substantial uncatalogued genetic variation with respect to known ARGs, although a relatively small proportion of these alleles are repeatedly observed in a large international dataset suggesting strong selection pressures. The current approach of using fuzzy matching for ARG detection, ignoring the unknown effects of uncatalogued variation, is unlikely to be acceptable for future clinical deployment. The association of synonymous mutations with potentially important phenotypic differences suggests that relying solely on amino acid-based gene detection to predict resistance is unlikely to be sufficient. Finally, the inability to explain all resistance using existing knowledge highlights the importance of new target gene discovery.

FUNDING

National Institute for Health and Care Research, Wellcome, and UK Medical Research Council.

Development and preliminary assessment of the iFIND TBR: all-in- one molecular diagnostic assay for rapid detection of Mycobacterium tuberculosis and rifampicin resistance

Introduction

Early and accurate diagnosis of tuberculosis (TB) is crucial for initiating timely treatment and preventing new infections. In this study, we introduced the iFIND TBR assay, an automated all-in-one tuberculosis detection approach that simultaneously detect Mycobacterium tuberculosis (MTB) and rifampicin (RIF) resistance.

Methods

The limits of detection (LOD), sensitivity, specificity, and RIF-R rpoB mutation detection of the iFIND TBR were tested on Mycobacterium tuberculosis DNA or sputum samples spiked with known numbers of M.tuberculosis H37Rv. Frozen clinical samples from patients suspected of having TB were also tested.

Results

The LOD of the iFIND TBR for MTB detection were 13.34 CFU/ml (95% CI, 11.71-16.47), and for RIF resistance was 109.79CFU/mL (95% CI, 95-138.19). The iFIND TBR assay accurately distinguish MTB strains from non-tuberculous mycobacteria (NTM) without any cross reactivity. Testing on 157 clinical sputum samples, compared with the bacteriologically TB standard, the overall sensitivity and specificity of the iFIND TBR was 100% (95%CI, 94.64, 100) and 85.29% (95% CI, 74.61, 92.72), respectively. When assessing RIF susceptibility, the iFIND TBR achieved a sensitivity of 98.15% (95% CI, 90.11-99.95) and a specificity of 85.71% (95% CI, 67.33-95.97), compared with phenotypic drug susceptibility testing. Discordant RIF susceptibility results were more frequently observed in samples exhibiting heteroresistance.

Discussion

These findings demonstrate that iFIND TBR assay performs well in detecting TB and RIF resistance, and shows promise as a point-of-care tool in resource-limited areas.

A novel dual probe-based method for mutation detection using isothermal amplification

Cost efficient and rapid detection tools to detect mutations especially those linked to drug-resistance are important to address concerns of the rising multi-drug resistance infections. Here we integrated dual probes, namely a calibrator probe and an indicator probe, into isothermal amplification detection system. These two probes are designed to bind distinct regions on the same amplicon to determine the presence or absence of mutation. The calibrator probe signal is used as an internal signal calibrator for indicator probe which detects the presence or absence of the mutation. As an illustrative example, we evaluated the applicability of this dual probe method for detecting mutations associated with rifampicin (RIF) drug resistance at codons 516, 526 and 531 of the rpoB gene in Mycobacterium tuberculosis. In this assessment, we examined 127 artificial samples comprising wild types and mutants with single or multiple mutations. Our results demonstrated 100% accuracy for both wild types and mutants for mutations at codons 526 and 531. As regards to mutations at codon 516, the wild type was identified with 100% accuracy, while the mutants were identified with 95% accuracy. Moreover, when we extended our evaluation to include clinical MTB strains and the Zeptometrix MTB Verification panel, our method achieved 100% accuracy (5 out of 5) in identifying wild-type strains. Additionally, we successfully detected a RIF-resistant strain with mutations at codon 531 of the rpoB gene in Zeptometrix verification panel. Our isothermal mutation detection system, relying on dual probes exhibits a versatile approach. With the capability to identify mutations without prior knowledge of their specific mutation direction, our dual-probe method shows significant promise for applications in drug resistance nucleic acid testing, particularly in resource-limited settings.

Nanopore-based targeted sequencing test for direct tuberculosis identification, genotyping, and detection of drug resistance mutations: a side-by-side comparison of targeted next-generation sequencing technologies

We investigated the performance of the targeted next-generation sequencing (tNGS)-based Oxford Nanopore Diagnostics AmPORE TB assay, recently approved by the World Health Organization (WHO) as tuberculosis (TB) diagnostic test for the detection of drug resistance on respiratory specimens. A total of 104 DNA samples from Xpert MTB/RIF-positive TB sputum specimens were tested using the AmPORE TB kit, with the GenoScreen Deeplex Myc-TB as a comparative tNGS assay. For AmPORE TB, DNA samples were divided into five sequencing runs on the MinION device. Data analysis was performed using proprietary software. The WHO catalog of mutations was used for drug resistance interpretation. The assay achieved a high validity rate of 98% (102/104 DNA samples), homogeneous mean reads coverage across TB-positive specimens, and 100% positive and negative agreements for detecting mutations associated with resistance to rifampicin, pyrazinamide, fluoroquinolones, ethambutol, and capreomycin compared with Deeplex Myc-TB. The main discrepancies for the remaining drugs were attributable to the different assay panel designs. The AmPORE TB turnaround time was approximately 5-6 hours from extracted DNA to tNGS reporting for batches of 22 DNA samples. The AmPORE TB assay drastically reduced the time to tNGS reporting from days to hours and showed good performance for drug-resistant TB profiling compared with Deeplex Myc-TB.

IMPORTANCE

Targeted next-generation sequencing (tNGS) of Mycobacterium tuberculosis provides comprehensive resistance predictions matched to new multidrug-resistant/rifampicin-resistant tuberculosis regimens and received World Health Organization approval for clinical use in respiratory samples in 2024. The advanced version of the Oxford Nanopore Diagnostics AmPORE TB tNGS kit was evaluated in this study for the first time and demonstrated good performance, flexibility, and faster turnaround time compared with the existing solutions.

Benchmarking reveals superiority of deep learning variant callers on bacterial nanopore sequence data

Variant calling is fundamental in bacterial genomics, underpinning the identification of disease transmission clusters, the construction of phylogenetic trees, and antimicrobial resistance detection. This study presents a comprehensive benchmarking of variant calling accuracy in bacterial genomes using Oxford Nanopore Technologies (ONT) sequencing data. We evaluated three ONT basecalling models and both simplex (single-strand) and duplex (dual-strand) read types across 14 diverse bacterial species. Our findings reveal that deep learning-based variant callers, particularly Clair3 and DeepVariant, significantly outperform traditional methods and even exceed the accuracy of Illumina sequencing, especially when applied to ONT's super-high accuracy model. ONT's superior performance is attributed to its ability to overcome Illumina's errors, which often arise from difficulties in aligning reads in repetitive and variant-dense genomic regions. Moreover, the use of high-performing variant callers with ONT's super-high accuracy data mitigates ONT's traditional errors in homopolymers. We also investigated the impact of read depth on variant calling, demonstrating that 10× depth of ONT super-accuracy data can achieve precision and recall comparable to, or better than, full-depth Illumina sequencing. These results underscore the potential of ONT sequencing, combined with advanced variant calling algorithms, to replace traditional short-read sequencing methods in bacterial genomics, particularly in resource-limited settings.

Drug-resistant tuberculosis: a persistent global health concern

Drug-resistant tuberculosis (TB) is estimated to cause 13% of all antimicrobial resistance-attributable deaths worldwide and is driven by both ongoing resistance acquisition and person-to-person transmission. Poor outcomes are exacerbated by late diagnosis and inadequate access to effective treatment. Advances in rapid molecular testing have recently improved the diagnosis of TB and drug resistance. Next-generation sequencing of Mycobacterium tuberculosis has increased our understanding of genetic resistance mechanisms and can now detect mutations associated with resistance phenotypes. All-oral, shorter drug regimens that can achieve high cure rates of drug-resistant TB within 6-9 months are now available and recommended but have yet to be scaled to global clinical use. Promising regimens for the prevention of drug-resistant TB among high-risk contacts are supported by early clinical trial data but final results are pending. A person-centred approach is crucial in managing drug-resistant TB to reduce the risk of poor treatment outcomes, side effects, stigma and mental health burden associated with the diagnosis. In this Review, we describe current surveillance of drug-resistant TB and the causes, risk factors and determinants of drug resistance as well as the stigma and mental health considerations associated with it. We discuss recent advances in diagnostics and drug-susceptibility testing and outline the progress in developing better treatment and preventive therapies.

Phylogenetically Informative Mutations in Drug Resistance Genes of Human-Infecting Mycobacterium bovis

The diagnosis of drug-resistant tuberculosis (TB) by molecular testing of Mycobacterium tuberculosis drug resistance genes is becoming increasingly common clinically. However, M. bovis, as an uncommon pathogen of human TB, may interfere with the test results. A comprehensive understanding of phylogenetically informative mutations in the drug resistance genes of M. bovis is required to distinguish true resistance-conferring mutations. We analyzed 53 drug resistance genes in 165 M. bovis isolated from humans using whole-genome sequencing data and found that 98.2% (162/165) of isolates have pyrazinamide intrinsic genotypic resistance, owing to the H57D mutation in the pncA gene. 12.1% (20/165) of M. bovis isolates were resistant to drugs other than pyrazinamide. Furthermore, we discovered 18 phylogenetically informative mutations that differed between M. bovis and the major lineages 1-4 of M. tuberculosis. Additionally, we reported false-positive ethambutol resistance caused by M. bovis infection due to the phylogenetically informative mutation embB E378A. This study is crucial for gaining insights into the genetic characterization and drug resistance of M. bovis prevalent in humans, as well as contributing to the development of more accurate molecular diagnostic methods and detection tools for drug resistance.

Genetic diversity within diagnostic sputum samples is mirrored in the culture of Mycobacterium tuberculosis across different settings

Culturing and genomic sequencing of Mycobacterium tuberculosis (MTB) from tuberculosis (TB) cases is the basis for many research and clinical applications. The alternative, culture-free sequencing from diagnostic samples, is promising but poses challenges to obtain and analyse the MTB genome. Paradoxically, culture is assumed to impose a diversity bottleneck, which, if true, would entail unexplored consequences. To unravel this paradox we generate high-quality genomes of sputum-culture pairs from two different settings after developing a workflow for sequencing from sputum and a tailored bioinformatics analysis. Careful downstream comparisons reveal sources of sputum-culture incongruences due to false positive/negative variation associated with factors like low input MTB DNA or variable genomic depths. After accounting for these factors, contrary to the bottleneck dogma, we identify a 97% variant agreement within sputum-culture pairs, with a high correlation also in the variants' frequency (0.98). The combined analysis from five different settings and more than 100 available samples shows that our results can be extrapolated to different TB epidemic scenarios, demonstrating that for the cases tested culture accurately mirrors clinical samples.

Unveiling the complexity of rifampicin drug susceptibility testing in Mycobacterium tuberculosis: comparative analysis with next-generation sequencing

Introduction. The discordance between phenotypic and molecular methods of rifampicin (RIF) drug susceptibility testing (DST) in Mycobacterium tuberculosis poses a significant challenge, potentially resulting in misdiagnosis and inappropriate treatment.Hypothesis/gap statement. A comparison of RIF phenotypic and molecular methods for DST, including whole genome sequencing (WGS), may provide a better understanding of resistance mechanisms.Aim. This study aims to compare RIF DST in M. tuberculosis using two phenotypic and molecular methods including the GeneXpert RIF Assay (GX) and WGS for better understanding.Methodology. The study evaluated two phenotypic liquid medium methods [Lowenstein-Jensen (LJ) and Mycobacterium Growth Indicator Tube (MGIT)], one targeted molecular method (GX), and one WGS method. Moreover, mutational frequency in ponA1 and ponA2 was also screened in the current and previous RIF resistance M. tuberculosis genomic isolates to find their compensatory role.Results. A total of 25 RIF-resistant isolates, including nine from treatment failures and relapse cases with both discordant and concordant DST results on LJ, MGIT and GX, were subjected to WGS. The phenotypic DST results indicated that 11 isolates (44%) were susceptible on LJ and MGIT but resistant on GX. These isolates exhibited multiple mutations in rpoB, including Thr444>Ala, Leu430>Pro, Leu430>Arg, Asp435>Gly, His445>Asn and Asn438>Lys. Conversely, four isolates that were susceptible on GX and MGIT but resistant on LJ were wild type for rpoB in WGS. However, these isolates possessed several novel mutations in the PonA1 gene, including a 10 nt insertion and two nonsynonymous mutations (Ala394>Ser, Pro631>Ser), as well as one nonsynonymous mutation (Pro780>Arg) in PonA2. The discordance rate of RIF DST is higher on MGIT than on LJ and GX when compared to WGS. These discordances in the Delhi/CAS lineages were primarily associated with failure and relapse cases.Conclusion. The WGS of RIF resistance is relatively expensive, but it may be considered for isolates with discordant DST results on MGIT, LJ and GX to ensure accurate diagnosis and appropriate treatment options.

A Profile of Drug-Resistant Mutations in Mycobacterium tuberculosis Isolates from Guangdong Province, China

Guangdong Province, China's largest economy, has a high incidence of tuberculosis (TB). At present, there are few reports on the distribution, transmission and drug resistance of Mycobacterium tuberculosis (Mtb) strains in this region. In this study, we performed minimum inhibitory concentration testing for 14 anti-TB drugs and whole-genome sequencing of 713 clinical Mtb isolates from 20,662 sputum culture-positive tuberculosis patients registered at 31 tuberculosis drug resistance surveillance sites covering 20 cities in Guangdong Province from 2016 to 2018. Moreover, we evaluated genome-wide associations between mutations and drug resistance, and further investigated the differences in the MICs of mutations. The epidemiology, drug-resistant phenotypes and whole genome sequencing data of 713 clinical Mtb isolates were analyzed, revealing the lineage distribution and drug-resistant gene profiles in Guangdong Province. WGS combined with quantitative MIC measurements identified several novel loci associated with resistance, of which 16 loci were found to be related to resistance to more than one drug. This study analyzed the lineage distribution, prevalence characteristics and resistance-corresponding gene profiles of Mtb isolates in Guangdong province, and provided a theoretical basis for the formulation of tuberculosis prevention and control policy in the province.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-024-01236-3.

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.

Update on the diagnosis of tuberculosis

BACKGROUND

Tuberculosis (TB) remains a global public health threat, and the development of rapid and precise diagnostic tools is the key to enabling the early start of treatment, monitoring response to treatment, and preventing the spread of the disease.

OBJECTIVES

An overview of recent progress in host- and pathogen-based TB diagnostics.

SOURCES

We conducted a PubMed search of recent relevant articles and guidelines on TB screening and diagnosis.

CONTENT

An overview of currently used methods and perspectives in the following areas of TB diagnostics is provided: immune-based diagnostics, X-ray, clinical symptoms and scores, cough detection, culture of Mycobacterium tuberculosis and identifying its resistance profile using phenotypic and genotypic methods, including next-generation sequencing, sputum- and non-sputum-based molecular diagnosis of TB and monitoring of response to treatment.

IMPLICATIONS

A brief overview of the most relevant advances and changes in international guidelines regarding screening and diagnosing TB is provided in this review. It aims at reviewing all relevant areas of diagnostics, including both pathogen- and host-based methods.

Detection of multidrug-resistance in Mycobacterium tuberculosis by phenotype- and molecular-based assays

BACKGROUND

The whole-genome sequencing (WGS) is becoming an increasingly effective tool for rapid and accurate detection of drug resistance in Mycobacterium tuberculosis complex (MTBC). This approach, however, has still been poorly evaluated on strains from Central and Eastern European countries. The purpose of this study was to assess the performance of WGS against conventional drug susceptibility testing (DST) for the detection of multi-drug resistant (MDR) phenotypes among MTBC clinical strains from Poland and Lithuania.

METHODS

The study included 208 MTBC strains (130 MDR; 78 drug susceptible), recovered from as many tuberculosis patients in Lithuania and Poland between 2018 and 2021. Resistance to rifampicin (RIF) and isoniazid (INH) was assessed by Critical Concentration (CC) and Minimum Inhibitory Concentration (MIC) DST as well as molecular-based techniques, including line-probe assay (LPA) and WGS. The analysis of WGS results was performed using bioinformatic pipeline- and software-based tools.

RESULTS

The results obtained with the CC DST were more congruent with those by LPA compared to pipeline-based WGS. Software-based tools showed excellent concordance with pipeline-based analysis in prediction of RIF/INH resistance. The RIF-resistant strains demonstrated a relatively homogenous MIC distribution with the mode at the highest tested MIC value. The most frequent RIF-resistance conferring mutation was rpoB S450L. The mode MIC for INH was two-fold higher among double katG and inhA mutants than among single katG mutants. The overall rate of discordant results between all methods was calculated at 5.3%. Three strains had discordant results by both genotypic methods (LPA and pipeline-based WGS), one strain by LPA only, three strains by MIC DST, two strains by both MIC DST and pipeline-based WGS, and the remaining two strains showed discordant results with all three methods, compared to CC DST.

CONCLUSIONS

Considering MIC DST results, current CCs of the first-line anti-TB drugs might be inappropriately high and may need to be revised. Both molecular methods demonstrated 100% specificity, while pipeline-based WGS had slightly lower sensitivity for RIF and INH than LPA, compared to CC DST.

An additional proofreader contributes to DNA replication fidelity in mycobacteria

The removal of mis-incorporated nucleotides by proofreading activity ensures DNA replication fidelity. Whereas the ε-exonuclease DnaQ is a well-established proofreader in the model organism Escherichia coli, it has been shown that proofreading in a majority of bacteria relies on the polymerase and histidinol phosphatase (PHP) domain of replicative polymerase, despite the presence of a DnaQ homolog that is structurally and functionally distinct from E. coli DnaQ. However, the biological functions of this type of noncanonical DnaQ remain unclear. Here, we provide independent evidence that noncanonical DnaQ functions as an additional proofreader for mycobacteria. Using the mutation accumulation assay in combination with whole-genome sequencing, we showed that depletion of DnaQ in Mycolicibacterium smegmatis leads to an increased mutation rate, resulting in AT-biased mutagenesis and increased insertions/deletions in the homopolymer tract. Our results showed that mycobacterial DnaQ binds to the β clamp and functions synergistically with the PHP domain proofreader to correct replication errors. Furthermore, the loss of dnaQ results in replication fork dysfunction, leading to attenuated growth and increased mutagenesis on subinhibitory fluoroquinolones potentially due to increased vulnerability to fork collapse. By analyzing the sequence polymorphism of dnaQ in clinical isolates of Mycobacterium tuberculosis (Mtb), we demonstrated that a naturally evolved DnaQ variant prevalent in Mtb lineage 4.3 may enable hypermutability and is associated with drug resistance. These results establish a coproofreading model and suggest a division of labor between DnaQ and PHP domain proofreader. This study also provides real-world evidence that a mutator-driven evolutionary pathway may exist during the adaptation of Mtb.

Evaluation of WHO catalog of mutations and five WGS analysis tools for drug resistance prediction of Mycobacterium tuberculosis isolates from China

The continuous advancement of molecular diagnostic techniques, particularly whole-genome sequencing (WGS), has greatly facilitated the early diagnosis of drug-resistant tuberculosis patients. Nonetheless, the interpretation of results from various types of mutations in drug-resistant-associated genes has become the primary challenge in the field of molecular drug-resistance diagnostics. In this study, our primary objective is to evaluate the diagnosis accuracy of the World Health Organization (WHO) catalog of mutations and five WGS analysis tools (PhyResSE, Mykrobe, TB Profiler, Gen-TB, and SAM-TB) in drug resistance to 10 anti-Mycobacterium tuberculosis (MTB) drugs. We utilized the data of WGS collected between 2014 and 2017 in Zhejiang Province, consisting of 110 MTB isolates as detailed in our previous study. Based on phenotypic drug susceptibility testing (DST) results using the proportion method on Löwenstein-Jensen medium with antibiotics, we evaluated the predictive accuracy of genotypic DST obtained by these tools. The results revealed that the WHO catalog of mutations and five WGS analysis tools exhibit robust predictive capabilities concerning resistance to isoniazid, rifampicin, ethambutol, streptomycin, amikacin, kanamycin, and capreomycin. Notably, Mykrobe, SAM-TB, and TB Profiler demonstrate the most accurate predictions for resistance to pyrazinamide, prothionamide, and para-aminosalicylic acid, respectively. These findings are poised to significantly guide and influence future clinical treatment strategies and resistance monitoring protocols.IMPORTANCEWhole-genome sequencing (WGS) has the potential for the early diagnosis of drug-resistant tuberculosis. However, the interpretation of mutations of drug-resistant-associated genes represents a significant challenge as the amount and complexity of WGS data. We evaluated the accuracy of the World Health Organization catalog of mutations and five WGS analysis tools in predicting drug resistance to first-line and second-line anti-TB drugs. Our results offer clinicians guidance on selecting appropriate WGS analysis tools for predicting resistance to specific anti-TB drugs.

Pan-lineage Mycobacterium tuberculosis reference genome for enhanced molecular diagnosis

In Mycobacterium tuberculosis (MTB) control, whole genome sequencing-based molecular drug susceptibility testing (molDST-WGS) has emerged as a pivotal tool. However, the current reliance on a single-strain reference limits molDST-WGS's true potential. To address this, we introduce a new pan-lineage reference genome, 'MtbRf'. We assembled 'unmapped' reads from 3,614 MTB genomes (751 L1; 881 L2; 1,700 L3; and 282 L4) into 35 shared, annotated contigs (54 coding sequences [CDSs]). We constructed MtbRf through: (1) searching for contig homologues among genome database that precipitate results uniquely within Mycobacteria genus; (2) comparing genomes with H37Rv ('lift-over') to define 18 insertions; and (3) filling gaps in H37Rv with insertions. MtbRf adds 1.18% sequences to H37rv, salvaging >60% of previously unmapped reads. Transcriptomics confirmed gene expression of new CDSs. The new variants provided a moderate DST predictive value (AUROC 0.60-0.75). MtbRf thus unveils previously hidden genomic information and lays the foundation for lineage-specific molDST-WGS.

Toxin-antitoxin system gene mutations driving Mycobacterium tuberculosis transmission revealed by whole genome sequencing

Background

The toxin-antitoxin (TA) system plays a vital role in the virulence and pathogenicity of Mycobacterium tuberculosis (M. tuberculosis). However, the regulatory mechanisms and the impact of gene mutations on M. tuberculosis transmission remain poorly understood.

Objective

To investigate the influence of gene mutations in the toxin-antitoxin system on M. tuberculosis transmission dynamics.

Method

We performed whole-genome sequencing on the analyzed strains of M. tuberculosis. The genes associated with the toxin-antitoxin system were obtained from the National Center for Biotechnology Information (NCBI) Gene database. Mutations correlating with enhanced transmission within the genes were identified by using random forest, gradient boosting decision tree, and generalized linear mixed models.

Results

A total of 13,518 M. tuberculosis isolates were analyzed, with 42.29% (n = 5,717) found to be part of genomic clusters. Lineage 4 accounted for the majority of isolates (n = 6488, 48%), followed by lineage 2 (n = 5133, 37.97%). 23 single nucleotide polymorphisms (SNPs) showed a positive correlation with clustering, including vapB1 G34A, vapB24 A76C, vapB2 T171C, mazF2 C85T, mazE2 G104A, vapB31 T112C, relB T226A, vapB11 C54T, mazE5 T344C, vapB14 A29G, parE1 (C103T, C88T), and parD1 C134T. Six SNPs, including vapB6 A29C, vapB31 T112C, parD1 C134T, vapB37 G205C, Rv2653c A80C, and vapB22 C167T, were associated with transmission clades across different countries. Notably, our findings highlighted the positive association of vapB6 A29C, vapB31 T112C, parD1 C134T, vapB37 G205C, vapB19 C188T, and Rv2653c A80C with transmission clades across diverse regions. Furthermore, our analysis identified 32 SNPs that exhibited significant associations with clade size.

Conclusion

Our study presents potential associations between mutations in genes related to the toxin-antitoxin system and the transmission dynamics of M. tuberculosis. However, it is important to acknowledge the presence of confounding factors and limitations in our study. Further research is required to establish causation and assess the functional significance of these mutations. These findings provide a foundation for future investigations and the formulation of strategies aimed at controlling TB transmission.

Surveillance of fluoroquinolones resistance in rifampicin-susceptible tuberculosis in eastern China with whole-genome sequencing-based approach

Background

Leveraging well-established DNA-level drug resistance mechanisms, whole-genome sequencing (WGS) has emerged as a valuable methodology for predicting drug resistance. As the most effective second-line anti-tuberculosis (anti-TB) drugs, fluoroquinoloness (FQs) are generally used to treat multidrug-resistant tuberculosis (MDR-TB, defined as being resistant to resistant to rifampicin and isoniazid) or rifampicin-resistant tuberculosis (RR-TB). However, FQs are also commonly used in the management of other bacterial infections. There are few published data on the rates of FQs resistance among rifampicin-susceptible TB. The prevalence of FQs resistance among TB patients who are rifampicin-susceptible has not been studied in Zhejiang Province, China. The goal of this study was to provide a baseline characterization of the prevalence of FQs resistance, particularly among rifampicin-susceptible TB in Zhejiang Province, China.

Methods

Based on WGS, we have investigated the prevalence of FQs resistance among rifampicin-susceptible TB in Zhejiang Province. All pulmonary TB patients with positive cultures who were identified in Zhejiang area during TB drug resistance surveillance from 2018 to 2019 have enrolled in this population-based retrospective study.

Results

The rate of FQs resistance was 4.6% (32/698) among TB, 4.0% (27/676) among rifampicin-susceptible TB, and 22.7% (5/22) among RR-TB. According to WGS, strains that differ within 12 single-nucleotide polymorphisms (SNPs) were considered to be transmission of FQ-resistant strains. Specifically, 3.7% (1/27) of FQs resistance was caused by the transmission of FQs-resistant strains among the rifampicin-susceptible TB and 40.7% (11/27) of FQs resistance was identified as hetero-resistance.

Conclusion

The prevalence of FQs resistance among TB patients who were rifampicin-susceptible was severe in Zhejiang. The emergence of FQs resistance in TB isolates that are rifampicin-susceptible was mainly caused by the selection of drug-resistant strains. In order to prevent the emergence of FQs resistance, the WGS-based surveillance system for TB should be urgently established, and clinical awareness of the responsible use of FQs for respiratory infections should be enhanced.

Design, synthesis and computational studies of new azaheterocyclic coumarin derivatives as anti-Mycobacterium tuberculosis agents targeting enoyl acyl carrier protein reductase (InhA)

In this study, we designed and synthesized a series of coumarin derivatives as antitubercular agents targeting the enoyl acyl carrier protein reductase (InhA) enzyme. Among the synthesized compounds, the tetrazole derivative 4c showed the most potent antitubercular effect with a minimum inhibitory concentration value (MIC) of 15 μg mL-1 against Mtb H37Rv and could also inhibit the growth of the mutant strain (ΔkatG). Compound 4c was able to penetrate Mtb-infected human macrophages and suppress the intracellular growth of tubercle bacilli. Moreover, the target derivative 4c showed a potent inhibitory effect against InhA enzyme with an IC50 value of 0.565 μM, which was superior to the reference InhA inhibitor triclosan. Molecular docking of compound 4c within the InhA active site revealed the importance of the 4-phenylcoumarin ring system and tetrazole moiety for activity. Finally, the physicochemical properties and pharmacokinetic parameters of 4c were investigated.

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.

Apramycin has high in vitro activity against Mycobacterium tuberculosis

Introduction. Aminoglycoside antibiotics such as amikacin and kanamycin are important components in the treatment of Mycobacterium tuberculosis (Mtb) infection. However, more and more clinical strains are found to be aminoglycoside antibiotic-resistant. Apramycin is another kind of aminoglycoside antibiotic that is commonly used to treat infections in animals.Hypothesis. Apramycin may have in vitro activity against Mtb.Aim. This study aims to evaluate the efficacy of apramycin against Mtb in vitro and determine its epidemiological cut-off (ECOFF) value.Methodology. One hundred Mtb isolates, including 17 pansusceptible and 83 drug-resistant tuberculosis (DR-TB) strains, were analysed for apramycin resistance using the MIC assay.Results. Apramycin exhibited significant inhibitory activity against Mtb clinical isolates, with an MIC50 of 0.5 μg ml-1 and an MIC90 of 1 μg ml-1. We determined the tentative ECOFF value as 1 µg ml-1 for apramycin. The resistant rates of multidrug-resistant tuberculosis (MDR-TB), pre-extensively drug-resistant (pre-XDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) strains were 12.12 % (4/33), 20.69 % (6/29) and 66.67 % (14/21), respectively. The rrs gene A1401G is associated with apramycin resistance, as well as the cross-resistance between apramycin and other aminoglycosides.Conclusion. Apramycin shows high in vitro activity against the Mtb clinical isolates, especially the MDR-TB clinical isolates. This encouraging discovery calls for more research on the functions of apramycin in vivo and as a possible antibiotic for the treatment of drug-resistant TB.

Evaluation of Whole Genome Sequencing-Based Predictions of Antimicrobial Resistance to TB First Line Agents: A Lesson from 5 Years of Data

Phenotypic susceptibility testing of the Mycobacterium tuberculosis complex (MTBC) isolate requires culture growth, which can delay rapid detection of resistant cases. Whole genome sequencing (WGS) and data analysis pipelines can assist in predicting resistance to antimicrobials used in the treatment of tuberculosis (TB). This study compared phenotypic susceptibility testing results and WGS-based predictions of antimicrobial resistance (AMR) to four first-line antimicrobials-isoniazid, rifampin, ethambutol, and pyrazinamide-for MTBC isolates tested between the years 2018-2022. For this 5-year retrospective analysis, the WGS sensitivity for predicting resistance for isoniazid, rifampin, ethambutol, and pyrazinamide using Mykrobe was 86.7%, 100.0%, 100.0%, and 47.8%, respectively, and the specificity was 99.4%, 99.5%, 98.7%, and 99.9%, respectively. The predictive values improved slightly using Mykrobe corrections applied using TB Profiler, i.e., the WGS sensitivity for isoniazid, rifampin, ethambutol, and pyrazinamide was 92.31%, 100%, 100%, and 57.78%, respectively, and the specificity was 99.63%. 99.45%, 98.93%, and 99.93%, respectively. The utilization of WGS-based testing addresses concerns regarding test turnaround time and enables analysis for MTBC member identification, antimicrobial resistance prediction, detection of mixed cultures, and strain genotyping, all through a single laboratory test. WGS enables rapid resistance detection compared to traditional phenotypic susceptibility testing methods using the WHO TB mutation catalog, providing an insight into lesser-known mutations, which should be added to prediction databases as high-confidence mutations are recognized. The WGS-based methods can support TB elimination efforts in Canada and globally by ensuring the early start of appropriate treatment, rapidly limiting the spread of TB outbreaks.

Discordant results between Xpert MTB/RIF assay and Bactec MGIT 960 culture system regarding the detection of rifampin-resistant Mycobacterium tuberculosis isolates in Wenzhou, China

This study aimed to assess the possible causes of discordant results between Xpert MTB/RIF (Xpert) and Bactec MGIT 960 Culture System (MGIT960) regarding rifampicin (RIF) susceptibility in Mycobacterium tuberculosis. Patients with previous RIF-resistant tuberculosis who were admitted to Wenzhou Central Hospital from January 2020 to December 2022 were enrolled. The isolates obtained from these patients were subjected to RIF susceptibility tests using Xpert and MGIT960, and the minimum inhibitory concentration (MIC) of RIF was determined by the MYCOTB MIC plate test. Additionally, molecular docking and molecular dynamics (MD) simulations were performed to evaluate the binding efficacy of rpoB and RIF based on rpoB mutations detected in the isolates with discordant RIF susceptibility results. A total of 28 isolates with discordant RIF susceptibility test results were detected, 15 of them were RIF susceptible with MICs ≤ 0.5 µg/mL. Twelve out of 15 isolates contained borderline RIF resistance-associated mutations [L430P (n = 6), H445N (n = 6)], 1 isolate had D435Y and Q429H double mutation, and the remaining 2 isolates had a silent (Q432Q) mutation. Compared with the affinity of RIF toward the wild type (WT) (-45.83 kcal/mol) by MD, its affinity toward L452P (-55.52 kcal/mol), D435Y (-47.39 kcal/mol), L430P (approximately -69.72 kcal/mol), H445N (-49.53 kcal/mol), and Q429H (-55.67 kcal/mol) increased. Borderline RIF resistance-associated mutations were the main cause for the discordant RIF susceptibility results between Xpert and MGIT960, and the mechanisms of the resistance need further investigated.IMPORTANCEThis study is aimed at assessing discordant results between Xpert MTB/RIF (Xpert) assay and Bactec MGIT 960 Culture System (MGIT960) regarding the detection of rifampicin (RIF)-resistant Mycobacterium tuberculosis isolates in Wenzhou, China. The discordant results of RIF between these two assays were mainly caused by borderline RIF resistance-associated mutations, subsequently by silent mutations of rpoB. Borderline RIF resistance- associated mutations detected in our study were demonstrated to not be affected by the affinity of rpoB and RIF by molecular dynamics, and the mechanism of resistance was needed to be clarified. For the discordant results of RIF by Xpert and MGIT960 that occurred, rpoB DNA sequencing was recommended to investigate its association with resistance to RIF.

Genetic determinants of resistance to antimicrobial therapeutics are rare in publicly available Clostridioides difficile genome sequences

OBJECTIVES

To determine the frequencies and clonal distributions of putative genetic determinants of resistance to antimicrobials applied for treatment of Clostridioides difficile infection (CDI), as documented in the genomic record.

METHODS

We scanned 26 557 C. difficile genome sequences publicly available from the EnteroBase platform for plasmids, point mutations and gene truncations previously reported to reduce susceptibility to vancomycin, fidaxomicin or metronidazole, respectively. We measured the antimicrobial susceptibility of 143 selected C. difficile isolates.

RESULTS

The frequency of mutations causing reduced susceptibility to vancomycin and metronidazole, respectively, increased strongly after 2000, peaking at up to 52% of all sequenced C. difficile genomes. However, both mutations declined sharply more recently, reflecting major changes in CDI epidemiology. We detected mutations associated with fidaxomicin resistance in several major genotypes, but found no evidence of international spread of resistant clones. The pCD-METRO plasmid, conferring metronidazole resistance, was detected in a single previously unreported C. difficile isolate, recovered from a hospital patient in Germany in 2008. The pX18-498 plasmid, putatively associated with decreased vancomycin susceptibility, was confined to related, recent isolates from the USA. Phenotype measurements confirmed that most of those genetic features were useful predictors of antibiotic susceptibility, even though ranges of MICs typically overlapped among isolates with and without specific mutations.

CONCLUSIONS

Genomic data suggested that resistance to therapeutic antimicrobial drugs is rare in C. difficile. Public antimicrobial resistance marker databases were not equipped to detect most of the genetic determinants relevant to antibiotic therapy of CDI.

Concordance of targeted and whole genome sequencing for Mycobacterium tuberculosis genotypic drug susceptibility testing

Targeted Next Generation Sequencing (tNGS) and Whole Genome Sequencing (WGS) are increasingly used for genotypic drug susceptibility testing (gDST) of Mycobacterium tuberculosis. Thirty-two multi-drugs resistant and 40 drug susceptible isolates from Madagascar were tested with Deeplex® Myc-TB and WGS using the Mykrobe analysis pipeline. Sixty-four of 72 (89 %) yielded concordant categorical gDST results for drugs tested by both assays. Mykrobe didn't detect pncA K96T, pncA Q141P, pncA H51P, pncA H82R, rrs C517T and rpsL K43R mutations, which were identified as minority variants in corresponding isolates by tNGS. One discrepancy (rrs C517T) was associated with insufficient sequencing depth on WGS. Deeplex® Myc-TB didn't detect inhA G-154A which isn't covered by the assay's amplification targets. Despite those targets being included in the Deeplex® Myc-TB assay, a pncA T47A and a deletion in gid were not identified in one isolate respectively. The evaluated WGS and tNGS gDST assays show high but imperfect concordance.

Combating antimicrobial resistance in malaria, HIV and tuberculosis

Antimicrobial resistance poses a significant threat to the sustainability of effective treatments against the three most prevalent infectious diseases: malaria, human immunodeficiency virus (HIV) infection and tuberculosis. Therefore, there is an urgent need to develop novel drugs and treatment protocols capable of reducing the emergence of resistance and combating it when it does occur. In this Review, we present an overview of the status and underlying molecular mechanisms of drug resistance in these three diseases. We also discuss current strategies to address resistance during the research and development of next-generation therapies. These strategies vary depending on the infectious agent and the array of resistance mechanisms involved. Furthermore, we explore the potential for cross-fertilization of knowledge and technology among these diseases to create innovative approaches for minimizing drug resistance and advancing the discovery and development of new anti-infective treatments. In conclusion, we advocate for the implementation of well-defined strategies to effectively mitigate and manage resistance in all interventions against infectious diseases.

Large-scale statistical analysis of Mycobacterium tuberculosis genome sequences identifies compensatory mutations associated with multi-drug resistance

Tuberculosis (TB), caused by Mycobacterium tuberculosis, has a significant impact on global health worldwide. The development of multi-drug resistant strains that are resistant to the first-line drugs isoniazid and rifampicin threatens public health security. Rifampicin and isoniazid resistance are largely underpinned by mutations in rpoB and katG respectively and are associated with fitness costs. Compensatory mutations are considered to alleviate these fitness costs and have been observed in rpoC/rpoA (rifampicin) and oxyR'-ahpC (isoniazid). We developed a framework (CompMut-TB) to detect compensatory mutations from whole genome sequences from a large dataset comprised of 18,396 M. tuberculosis samples. We performed association analysis (Fisher's exact tests) to identify pairs of mutations that are associated with drug-resistance, followed by mediation analysis to identify complementary or full mediators of drug-resistance. The analyses revealed several potential mutations in rpoC (N = 47), rpoA (N = 4), and oxyR'-ahpC (N = 7) that were considered either 'highly likely' or 'likely' to confer compensatory effects on drug-resistance, including mutations that have previously been reported and validated. Overall, we have developed the CompMut-TB framework which can assist with identifying compensatory mutations which is important for more precise genome-based profiling of drug-resistant TB strains and to further understanding of the evolutionary mechanisms that underpin drug-resistance.

Discovery of potent antimycobacterial agents targeting lumazine synthase (RibH) of Mycobacterium tuberculosis

Tuberculosis (TB) continues to be a global health crisis, necessitating urgent interventions to address drug resistance and improve treatment efficacy. In this study, we validate lumazine synthase (RibH), a vital enzyme in the riboflavin biosynthetic pathway, as a potential drug target against Mycobacterium tuberculosis (M. tb) using a CRISPRi-based conditional gene knockdown strategy. We employ a high-throughput molecular docking approach to screen ~ 600,000 compounds targeting RibH. Through in vitro screening of 55 shortlisted compounds, we discover 3 compounds that exhibit potent antimycobacterial activity. These compounds also reduce intracellular burden of M. tb during macrophage infection and prevent the resuscitation of the nutrient-starved persister bacteria. Moreover, these three compounds enhance the bactericidal effect of first-line anti-TB drugs, isoniazid and rifampicin. Corroborating with the in silico predicted high docking scores along with favourable ADME and toxicity profiles, all three compounds demonstrate binding affinity towards purified lumazine synthase enzyme in vitro, in addition these compounds exhibit riboflavin displacement in an in vitro assay with purified lumazine synthase indicative of specificity of these compounds to the active site. Further, treatment of M. tb with these compounds indicate reduced production of flavin adenine dinucleotide (FAD), the ultimate end product of the riboflavin biosynthetic pathway suggesting the action of these drugs on riboflavin biosynthesis. These compounds also show acceptable safety profile in mammalian cells, with a high selective index. Hence, our study validates RibH as an important drug target against M. tb and identifies potent antimycobacterial agents.

Risk factors of adult isoniazid-resistant and rifampicin-susceptible tuberculosis in Nanjing, 2019-2021

INTRODUCTION

This study aimed to analyze the risk factors associated with isoniazid-resistant and rifampicin-susceptible tuberculosis (Hr-TB) in adults.

METHOD

The clinical data of 1,844 adult inpatients diagnosed with culture-positive pulmonary tuberculosis (PTB) in Nanjing Second Hospital from January 2019 and December 2021 were collected. All culture positive strain from the patient specimens underwent drug susceptibility testing (DST). Among them, 166 patients with Hr-TB were categorized as the Hr-TB group, while the remaining 1,678 patients were classified as having drug-susceptible tuberculosis (DS-TB). Hierarchical logistic regression was employed for multivariate analysis to identify variables associated with Hr-TB.

RESULTS

Multivariate logistic regression analysis revealed that individuals with diabetes mellitus (DM) (OR 1.472, 95% CI 1.037-2.088, p = 0.030) and a history of previous tuberculosis treatment (OR 2.913, 95% CI 1.971-4.306, p = 0.000) were at higher risk of developing adult Hr-TB, with this risk being more pronounced in male patients. Within the cohort, 1,640 patients were newly treated, and among them, DM (OR 1.662, 95% CI 1.123-2.461, p = 0.011) was identified as risk factors for Hr-TB.

CONCLUSIONS

Diabetes mellitus is a risk factor for Hr-TB in adults, and the contribution of diabetes as a risk factor was more pronounced in the newly treatment or male subgroup. And previous TB treatment history is also a risk factor for Hr-TB in adults.

Revealing the pathogenesis of gastric intestinal metaplasia based on the mucosoid air-liquid interface

BACKGROUND

Gastric intestinal metaplasia (GIM) is an essential precancerous lesion. Although the reversal of GIM is challenging, it potentially brings a state-to-art strategy for gastric cancer therapeutics (GC). The lack of the appropriate in vitro model limits studies of GIM pathogenesis, which is the issue this work aims to address for further studies.

METHOD

The air-liquid interface (ALI) model was adopted for the long-term culture of GIM cells in the present work. This study conducted Immunofluorescence (IF), quantitative real-time polymerase chain reaction (qRT-PCR), transcriptomic sequencing, and mucoproteomic sequencing (MS) techniques to identify the pathways for differential expressed genes (DEGs) enrichment among different groups, furthermore, to verify novel biomarkers of GIM cells.

RESULT

Our study suggests that GIM-ALI model is analog to the innate GIM cells, which thus can be used for mucus collection and drug screening. We found genes MUC17, CDA, TRIM15, TBX3, FLVCR2, ONECUT2, ACY3, NMUR2, and MAL2 were highly expressed in GIM cells, while GLDN, SLC5A5, MAL, and MALAT1 showed down-regulated, which can be used as potential biomarkers for GIM cells. In parallel, these genes that highly expressed in GIM samples were mainly involved in cancer-related pathways, such as the MAPK signal pathway and oxidative phosphorylation signal pathway.

CONCLUSION

The ALI model is validated for the first time for the in vitro study of GIM. GIM-ALI model is a novel in vitro model that can mimic the tissue micro-environment in GIM patients and further provide an avenue for studying the characteristics of GIM mucus. Our study identified new markers of GIM as well as pathways associated with GIM, which provides outstanding insight for exploring GIM pathogenesis and potentially other related conditions.

Whole-Genome Sequencing Predicting Phenotypic Antitubercular Drug Resistance: Meta-analysis

BACKGROUND

For simultaneous prediction of phenotypic drug susceptibility test (pDST) for multiple antituberculosis drugs, the whole genome sequencing (WGS) data can be analyzed using either a catalog-based approach, wherein 1 causative mutation suggests resistance, (eg, World Health Organization catalog) or noncatalog-based approach using complicated algorithm (eg, TB-profiler, machine learning). The aim was to estimate the predictive ability of WGS-based tests with pDST as the reference, and to compare the 2 approaches.

METHODS

Following a systematic literature search, the diagnostic test accuracies for 14 drugs were pooled using a random-effect bivariate model.

RESULTS

Of 779 articles, 44 with 16 821 specimens for meta-analysis and 13 not for meta-analysis were included. The areas under summary receiver operating characteristic curve suggested test accuracy was excellent (0.97-1.00) for 2 drugs (isoniazid 0.975, rifampicin 0.975), very good (0.93-0.97) for 8 drugs (pyrazinamide 0.946, streptomycin 0.952, amikacin 0.968, kanamycin 0.963, capreomycin 0.965, para-aminosalicylic acid 0.959, levofloxacin 0.960, ofloxacin 0.958), and good (0.75-0.93) for 4 drugs (ethambutol 0.926, moxifloxacin 0.896, ethionamide 0.878, prothionamide 0.908). The noncatalog-based and catalog-based approaches had similar ability for all drugs.

CONCLUSIONS

WGS accurately identifies isoniazid and rifampicin resistance. For most drugs, positive WGS results reliably predict pDST positive. The 2 approaches had similar ability.

CLINICAL TRIALS REGISTRATION

UMIN-ID UMIN000049276.

Rapid resistance detection is reliable for prompt adaptation of isoniazid resistant tuberculosis management

Objectives

Appropriate tuberculosis (TB) management requires anti-TB drugs resistance detection. We assessed the performance of rapid resistance detection assays and their impact on treatment adaptation, focusing on isoniazid resistant (Hr) TB.

Methods

From 2016 to 2022, all TB cases enrolled in 3 hospitals were reviewed for phenotypic drug susceptibility testing (p-DST) and genotypic DST (g-DST) performed by rapid molecular testing, and next generation sequencing (NGS). Clinical characteristics, treatment and outcome were collected for Hr-TB patients. The concordance between g-DST and p-DST results, and delay between treatment initiation and results of g-DST and p-DST were respectively recorded to assess the contribution of DST results on Hr-TB management.

Results

Among 654 TB cases enrolled, 29 were Hr-TB. Concordance between g-DST by rapid molecular methods and p-DST was 76.9 %, whilst concordance between NGS-based g-DST and p-DST was 98.7 %. Rapid resistance detection significantly fastened Hr-TB treatment adaptation (median delay between g-DST results and treatment modification was 6 days). It consisted in fluoroquinolone implementation for 17/23 patients; outcome was favourable except for 2 patients who died before DST reporting.

Conclusion

Rapid resistance detection fastened treatment adaptation. Also, NGS-based g-DST showed almost perfect concordance with p-DST, thus providing rapid and safe culture-free DST alternative.

Transcriptomic responses to antibiotic exposure in Mycobacterium tuberculosis

Transcriptional responses in bacteria following antibiotic exposure offer insights into antibiotic mechanism of action, bacterial responses, and characterization of antimicrobial resistance. We aimed to define the transcriptional antibiotic response (TAR) in Mycobacterium tuberculosis (Mtb) isolates for clinically relevant drugs by pooling and analyzing Mtb microarray and RNA-seq data sets. We generated 99 antibiotic transcription profiles across 17 antibiotics, with 76% of profiles generated using 3-24 hours of antibiotic exposure and 49% within one doubling of the WHO antibiotic critical concentration. TAR genes were time-dependent, and largely specific to the antibiotic mechanism of action. TAR signatures performed well at predicting antibiotic exposure, with the area under the receiver operating curve (AUC) ranging from 0.84-1.00 (TAR <6 hours of antibiotic exposure) and 0.76-1.00 (>6 hours of antibiotic exposure) for upregulated genes and 0.57-0.90 and 0.87-1.00, respectfully, for downregulated genes. This work desmonstrates that transcriptomics allows for the assessment of antibiotic activity in Mtb within 6 hours of exposure.