Diversified lineages and drug-resistance profiles of clinical isolates of Mycobacterium tuberculosis complex in Malaysia

Predominance of the East-Asian Beijing genotype in a Mycobacterium tuberculosis drug-resistant population in Central Malaysia

OBJECTIVES

Previous diversity studies on local Mycobacterium tuberculosis (MTB) isolates with or without antibiotic resistance, showed predominance of Indo-Oceanic EAI strains. This study focused specifically on a drug-resistant MTB population from central Malaysia and aimed to investigate the genotypes and resistance patterns involved.

METHODS

Whole-genome sequencing was performed on 56 local MTB isolates with known rifampicin-resistance or multidrug-resistance towards 13 anti-TB agents. Analysis of each genome sequence was performed using the widely recognized online MTB genotyping platforms, TBProfiler and Mykrobe to determine lineage and genotypic drug-resistance profile.

RESULTS

Forty (71.4%) isolates were identified as East-Asian Beijing strains. Phenotypic to genotypic antibiotic resistance patterns differed in 33 isolates (58.9%), with one isolate showing extensive drug resistance (XDR) that was previously not detected by conventional drug-susceptibility testing.

CONCLUSIONS

This drug-resistance population study demonstrated predominance of the East-Asian Beijing strains and a newly detected extensively drug-resistant MTB (XDR-TB) isolate in Malaysia. Information regarding association between lineage and drug-resistance TB in Malaysia is scarce, and more studies are needed to determine significance of such association, if any, in our local settings.

Human tuberculosis and Mycobacterium tuberculosis complex: A review on genetic diversity, pathogenesis and omics approaches in host biomarkers discovery

Mycobacterium tuberculosis complex (MTBC) refers to a group of mycobacteria encompassing nine members of closely related species that causes tuberculosis in animals and humans. Among the nine members, Mycobacterium tuberculosis (M. tuberculosis) remains the main causative agent for human tuberculosis that results in high mortality and morbidity globally. In general, MTBC species are low in diversity but exhibit distinctive biological differences and phenotypes among different MTBC lineages. MTBC species are likely to have evolved from a common ancestor through insertions/deletions processes resulting in species speciation with different degrees of pathogenicity. The pathogenesis of human tuberculosis is complex and remains poorly understood. It involves multi-interactions or evolutionary co-options between host factors and bacterial determinants for survival of the MTBC. Granuloma formation as a protection or survival mechanism in hosts by MTBC remains controversial. Additionally, MTBC species are capable of modulating host immune response and have adopted several mechanisms to evade from host immune attack in order to survive in humans. On the other hand, current diagnostic tools for human tuberculosis are inadequate and have several shortcomings. Numerous studies have suggested the potential of host biomarkers in early diagnosis of tuberculosis, in disease differentiation and in treatment monitoring. "Multi-omics" approaches provide holistic views to dissect the association of MTBC species with humans and offer great advantages in host biomarkers discovery. Thus, in this review, we seek to understand how the genetic variations in MTBC lead to species speciation with different pathogenicity. Furthermore, we also discuss how the host and bacterial players contribute to the pathogenesis of human tuberculosis. Lastly, we provide an overview of the journey of "omics" approaches in host biomarkers discovery in human tuberculosis and provide some interesting insights on the challenges and directions of "omics" approaches in host biomarkers innovation and clinical implementation.