The Evolution of Strain Typing in the Mycobacterium tuberculosis Complex

Area of Science:

• Microbiology
• Epidemiology
• Genetics

Background:

• Tuberculosis (TB) is a complex contagious disease requiring robust molecular typing for epidemiological surveillance and understanding pathogen diversity.
• Traditional methods like IS6110 DNA fingerprinting have been largely superseded by MIRU-VNTR typing due to its efficiency and standardized nomenclature.
• Whole genome sequencing (WGS) is emerging as a powerful tool for comprehensive genetic analysis of Mycobacterium tuberculosis complex (MTBC) strains.

Purpose of the Study:

• To provide an overview of the evolution of MTBC genotyping methods over the past three decades.
• To discuss the advantages and limitations of classical and WGS-based typing techniques.
• To identify current challenges and future directions for WGS standardization in TB research.

Main Methods:

• Review of historical and current molecular typing techniques for MTBC, including IS6110, MIRU-VNTR, spoligotyping, and whole genome sequencing (WGS).
• Comparative analysis of the strengths and weaknesses of each method regarding turnaround time, data output, and application scope.
• Discussion of challenges associated with WGS data analysis, standardization, and interpretation for epidemiological studies.

Main Results:

• MIRU-VNTR typing, often combined with spoligotyping, is the current gold standard for many TB genotyping applications, offering a balance of resolution and practicality.
• WGS provides near-complete genetic information, enabling deeper insights into MTBC diversity and evolution, but faces challenges in standardization and data sharing.
• The choice of genotyping method depends on the specific research question, ranging from outbreak investigations to large-scale surveillance.

Conclusions:

• The field of MTBC genotyping has evolved significantly, moving towards high-resolution WGS methods.
• Standardization of WGS analysis pipelines and global data sharing are critical for maximizing its potential in TB control.
• Future efforts should focus on developing standardized WGS approaches and clear guidelines for interpreting genomic distances to define transmission clusters effectively.