Insight into the drug resistance whole genome of Mycobacterium tuberculosis isolates from Khyber Pakhtunkhwa, Pakistan

Exploring therapeutic paradigm focusing on genes, proteins, and pathways to combat leprosy and tuberculosis: A network medicine and drug repurposing approach

BACKGROUND

Leprosy and tuberculosis caused by Mycobacterium leprae and Mycobacterium tuberculosis, respectively, are chronic infections with significant public health implications. While leprosy affects the skin and peripheral nerves and tuberculosis primarily targets the lungs, both diseases involve systemic immune responses. This study integrates transcriptomic analysis cheminformatics and molecular dynamics simulations to identify molecular mechanisms and potential therapeutic targets.

METHODS

Transcriptomic datasets were analyzed to identify dysregulated genes and pathways. Pathway enrichment tissue-specific and bulk RNA-seq expression analyses provided biological context. System biology networks revealed regulatory hub genes and molecular docking studies evaluated CHEMBL compounds as potential therapeutics. Molecular dynamics (MD) simulations assessed the stability of top ligand-protein complexes through RMSD RMSF and MM-GBSA free energy calculations.

RESULTS

Gene expression analysis identified 13 core dysregulated genes, including HSP90AA1 MAPK8IP3 and ZMPSTE24. Tissue-specific expression localized pivotal genes to lung tissues and immune cells with HSP90AA1 highly expressed in alveolar macrophages and epithelial cells. HSP90AA1 gene emerged as a central hub gene with 96 interactions involved in stress response pathways. Docking studies identified CHEMBL3653862 and CHEMBL3653884 with strong binding affinities (-10.16 to -12.69 kcal/mol) interacting with Asp93 and Tyr139. MD simulations confirmed binding stability with RMSD fluctuations within 2.1-3.5 Å and MM-GBSA energy values supporting ligand-protein stability.

CONCLUSION

This study identifies HSP90AA1 as a potential drug target in leprosy and tuberculosis. Findings support host-directed therapy approaches and highlight the importance of computational modeling in accelerating drug discovery. The study provides a foundation for future experimental validation, including in vitro and in vivo testing to advance drug repurposing strategies for these chronic infections.

Deciphering the mechanism of resistance by novel double mutations in pncA in Mycobacterium tuberculosis using protein structural graphs (PSG) and structural bioinformatic approaches

The evolution of MDR and XDR-TB is a growing concern and public health safety threat around the world. Gene mutations are the prime cause of drug resistance in tuberculosis, however the reports of double mutations further aggravated the situation. Despite the large-scale genomic sequencing and identification of novel mutations, structure investigation of the protein is still required to structurally and functionally characterize these novel mutations to design novel drugs for improved clinical outcome. Hence, we used structural bioinformatics approaches i.e. molecular modeling, residues communication and molecular simulation to understand the impact of novel double S59Y-L85P, D86G-V180F and S104G-V130 M mutation on the structure, function of pncA encoded Pyrazinamidase (PZase) and resistance of Pyrazinamide (PZA). Our results revealed that these mutations alter the binding paradigm and destabilize the protein to release the drug. Protein commination network (PCN) revealed variations in the hub residues and sub-networks which consequently alter the internal communication and signaling. The region 1-75 demonstrated higher flexibility in the mutant structures and minimal by the wild type which destabilize of the internally arranged beta-sheets which consequently reduce the binding of PZA and potentially Fe ion in the mutants. Hydrogen bonding analysis further validated the findings. The total binding free energy (ΔG) for each complex i.e. wild type -7.46 kcal/mol, S59Y-L85P -5.21 kcal/mol, S104G-V130 M -5.33 kcal/mol while for the D86G-V180F mutant the TBE was calculated to be -6.26 kcal/mol. This further confirms that these mutations reduce the binding energy of PZA for PZase and causes resistance in the effective therapy for TB. The trajectories motion was also observed to be affected by these mutations. In conclusion, these mutations use destabilizing approach to reduce the binding of PZA and causes resistance. These features can be used to design novel structure-based drugs against Tuberculosis.

Pretomanid development and its clinical roles in treating tuberculosis

Tuberculosis (TB) is the leading infectious cause of mortality worldwide. Despite the development of different antituberculosis drugs, managing resistant mycobacteria is still challenging. The discovery of novel drugs and new methods of targeted drug delivery have the potential to improve treatment outcomes, lower the duration of treatment, and reduce adverse events. Following bedaquiline and delamanid, pretomanid is the third medicine approved as part of a novel drug regimen for treating drug-resistant TB. It is a promising drug that has the capacity to shape TB treatment and achieve the End TB strategy set by the World Health Organization. The effectiveness of pretomanid has been reported in different observational and clinical studies. However, long-term safety data in humans are not yet available and the pretomanid-based regimen is recommended under an operational research framework that prohibits its wider and programmatic use. Further research is needed before pretomanid can be celebrated as a promising candidate for the treatment of different categories of TB and specific patients. This review covers the update on pretomanid development and its clinical roles in treating Mycobacterium tuberculosis.

Diversity and novel mutations in membrane transporters of Mycobacterium tuberculosis

Mycobacterium tuberculosis (MTB), the causative agent of tuberculosis (TB), encodes a family of membrane proteins belonging to Resistance-Nodulation-Cell Division (RND) permeases also called multidrug resistance pumps. Mycobacterial membrane protein Large (MmpL) transporters represent a subclass of RND transporters known to participate in exporting of lipid components across the cell envelope. These proteins perform an essential role in MTB survival; however, there are no data regarding mutations in MmpL, polyketide synthase (PKS) and acyl-CoA dehydrogenase FadE proteins from Khyber Pakhtunkhwa, Pakistan. This study aimed to screen mutations in transmembrane transporter proteins including MmpL, PKS and Fad through whole-genome sequencing (WGS) in local isolates of Khyber Pakhtunkhwa province, Pakistan. Fourteen samples were collected from TB patients and drug susceptibility testing was performed. However, only three samples were completely sequenced. Moreover, 209 whole-genome sequences of the same geography were also retrieved from NCBI GenBank to analyze the diversity of mutations in MmpL, PKS and Fad proteins. Among the 212 WGS (Accession ID: PRJNA629298, PRJNA629388, and ERR2510337-ERR2510345, ERR2510546-ERR2510645), numerous mutations in Fad (n = 756), PKS (n = 479), and MmpL (n = 306) have been detected. Some novel mutations were also detected in MmpL, PKS and acyl-CoA dehydrogenase Fad. Novel mutations including Asn576Ser in MmpL8, Val943Gly in MmpL9 and Asn145Asp have been detected in MmpL3. The presence of a large number of mutations in the MTB membrane may have functional consequences on proteins. However, further experimental studies are needed to elucidate the variants' effect on MmpL, PKS and FadE functions.

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

Purpose

The emergence of drug-resistant tuberculosis (DR-TB) represents a threat to the control of tuberculosis. This study aimed to estimate the patterns and trends of DR-TB in patients with suspected DR-TB. In addition, risk factors for multidrug-resistant tuberculosis (MDR-TB) were identified among suspected DR-TB patients in Dalian, China.

Patients and Methods

A total of 5661 patients with suspected DR-TB from Jan 1, 2013 to Dec 31, 2020 were included in the final analysis. The resistance pattern of all resistant strains was determined by drug susceptibility testing (DST) using the conventional Lowenstein-Jensen Proportion Method (LJ). DR-TB trends were estimated from 2013 to 2020. During the research period, the chi-square test was employed to analyze the significance of linear drug-resistance trends across time. Bivariate and multivariate logistic regression were performed to assess factors associated with MDR-TB.

Results

From 2013 to 2020, the resistance rates of rifampicin (RFP) and isoniazid (INH) decreased significantly, whereas the resistance rates of ethambutol (EMB) and streptomycin (SM) increased in patients with suspected DR-TB. From 2013 to 2020, the prevalence of DR-TB decreased in all patients from 34.71% to 28.01% with an average annual decrease of 3.02%. Among new cases, from 2013 to 2020, the prevalence of DR-TB (from 26.67% to 24.75%), RFP-resistant TB (RR-TB) (from 15.09% to 3.00%) and MDR-TB (from 6.08% to 2.62%) showed a significant downward trend. Among patients with a previous treatment history, DR-TB (from 54.70% to 37.50%), RR-TB (from 44.16% to 11.49%) and MDR-TB (from 26.90% to 10.34%) showed a significant downward trend from 2013 to 2020. Males (AOR 1.28, 95% CI 1.035–1.585), patients 45 to 64 years of age (AOR 1.75, 95% CI 1.342–2.284), patients 65 years and older (AOR 1.65, 95% CI 1.293–2.104), rural residents (AOR 1.24, 95% CI 1.014–1.519) and a previous treatment history (AOR 3.94, 95% CI 3.275–4.741) were risk factors for MDR-TB.

Conclusion

The prevalence of DR-TB, RR-TB and MDR-TB was significantly reduced from 2013 to 2020. Considerable progress has been made in the prevention and treatment of DR-TB during this period. However, the increasing rate of drug resistance in EMB and SM should be taken seriously. Suspected DR-TB patients who are male, older than 45 years of age, live in rural areas, and have a history of TB treatment should be given priority by health care providers.

Novel Mutations in Putative Nicotinic Acid Phosphoribosyltransferases of Mycobacterium tuberculosis and Their Effect on Protein Thermodynamic Properties

pncB1 and pncB2 are two putative nicotinic acid phosphoribosyltransferases, playing a role in cofactor salvage and drug resistance in Mycobacterium tuberculosis. Mutations have been reported in first- and second-line drug targets, causing resistance. However, pncB1 and pncB2 mutational data are not available, and neither of their mutation effects have been investigated in protein structures. The current study has been designed to investigate mutations and also their effects on pncB1 and pncB2 structures. A total of 287 whole-genome sequenced data of drug-resistant Mycobacterium tuberculosis isolates from Khyber Pakhtunkhwa of Pakistan were retrieved (BioSample PRJEB32684, ERR2510337-ERR2510445, ERR2510546-ERR2510645) from NCBI. The genomic data were analyzed for pncB1 and pncB2 mutations using PhyResSE. All the samples harbored numerous synonymous and non-synonymous mutations in pncB1 and pncB2 except one. Mutations Pro447Ser, Arg286Arg, Gly127Ser, and delTCAGGCCG1499213>1499220 in pncB1 are novel and have not been reported in literature and TB databases. The most common non-synonymous mutations exhibited stabilizing effects on the pncB1 structure. Moreover, 36 out of 287 samples harbored two non-synonymous and 34 synonymous mutations in pncB2 among which the most common was Phe204Phe (TTT/TTC), present in 8 samples, which may have an important effect on the usage of specific codons that may increase the gene expression level or protein folding effect. Mutations Ser120Leu and Pro447Ser, which are present in the loop region, exhibited a gain in flexibility in the surrounding residues while Gly429Ala and Gly127Ser also demonstrated stabilizing effects on the protein structure. Inhibitors designed based on the most common pncB1 and pncB2 mutants may be a more useful strategy in high-burden countries. More studies are needed to elucidate the effect of synonymous mutations on organism phenotype.

WITHDRAWN: Pretomanid for the treatment of Mycobacterium tuberculosis: Evidence on the development and clinical roles

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Characterization of rifampicin-resistant Mycobacterium tuberculosis in Khyber Pakhtunkhwa, Pakistan

Tuberculosis (TB), caused by Mycobacterium tuberculosis, is endemic in Pakistan. Resistance to both firstline rifampicin and isoniazid drugs (multidrug-resistant TB; MDR-TB) is hampering disease control. Rifampicin resistance is attributed to rpoB gene mutations, but rpoA and rpoC loci may also be involved. To characterise underlying rifampicin resistance mutations in the TB endemic province of Khyber Pakhtunkhwa, we sequenced 51 M. tuberculosis isolates collected between 2016 and 2019; predominantly, MDR-TB (n = 44; 86.3%) and lineage 3 (n = 30, 58.8%) strains. We found that known mutations in rpoB (e.g. S405L), katG (e.g. S315T), or inhA promoter loci explain the MDR-TB. There were 24 unique mutations in rpoA, rpoB, and rpoC genes, including four previously unreported. Five instances of within-host resistance diversity were observed, where two were a mixture of MDR-TB strains containing mutations in rpoB, katG, and the inhA promoter region, as well as compensatory mutations in rpoC. Heteroresistance was observed in two isolates with a single lineage. Such complexity may reflect the high transmission nature of the Khyber Pakhtunkhwa setting. Our study reinforces the need to apply sequencing approaches to capture the full-extent of MDR-TB genetic diversity, to understand transmission, and to inform TB control activities in the highly endemic setting of Pakistan.

Insights Into Mutations Induced Conformational Changes and Rearrangement of Fe2+ Ion in pncA Gene of Mycobacterium tuberculosis to Decipher the Mechanism of Resistance to Pyrazinamide

Pyrazinamide (PZA) is the first-line drug commonly used in treating Mycobacterium tuberculosis (Mtb) infections and reduces treatment time by 33%. This prodrug is activated and converted to an active form, Pyrazinoic acid (POA), by Pyrazinamidase (PZase) enzyme. Mtb resistance to PZA is the outcome of mutations frequently reported in pncA, rpsA, and panD genes. Among the mentioned genes, pncA mutations contribute to 72-99% of the total resistance to PZA. Thus, considering the vital importance of this gene in PZA resistance, its frequent mutations (D49N, Y64S, W68G, and F94A) were investigated through in-depth computational techniques to put conclusions that might be useful for new scaffolds design or structure optimization to improve the efficacy of the available drugs. Mutants and wild type PZase were used in extensive and long-run molecular dynamics simulations in triplicate to disclose the resistance mechanism induced by the above-mentioned point mutations. Our analysis suggests that these mutations alter the internal dynamics of PZase and hinder the correct orientation of PZA to the enzyme. Consequently, the PZA has a low binding energy score with the mutants compared with the wild type PZase. These mutations were also reported to affect the binding of Fe2+ ion and its coordinated residues. Conformational dynamics also revealed that β-strand two is flipped, which is significant in Fe2+ binding. MM-GBSA analysis confirmed that these mutations significantly decreased the binding of PZA. In conclusion, these mutations cause conformation alterations and deformities that lead to PZA resistance.