Related Experiment Video
Updated: Aug 3, 2025
07:35
Demonstrating a Multi-drug Resistant Mycobacterium tuberculosis Amplification Microarray
Published on: April 25, 2014
12.8K
Pyrazinamide-resistant Tuberculosis Obscured From Common Targeted Molecular Diagnostics
Samuel J Modlin1, Mikael Mansjö2, Jim Werngren2
1Laboratory for Pathogenesis of Clinical Drug Resistance and Persistence, School of Public Health, San Diego State University, San Diego, CA, USA.
Summary
A tuberculosis case resistant to pyrazinamide was misdiagnosed as susceptible due to a minority susceptible subpopulation masking the resistant majority. This highlights limitations in molecular diagnostics for detecting resistant tuberculosis strains.
Area of Science:
- Microbiology
- Genomics
- Clinical Diagnostics
Background:
- Tuberculosis (TB) diagnosis relies on accurate susceptibility testing.
- Molecular diagnostics are increasingly used but can be limited by genetic variations.
- Pyrazinamide resistance (PZA-R) in TB poses a significant treatment challenge.
Purpose of the Study:
- To report a clinical case of PZA-resistant TB misidentified as PZA-susceptible (PZA-S) by standard molecular diagnostics.
- To investigate the underlying genetic mechanism causing this diagnostic discrepancy.
- To highlight the impact of subpopulation dynamics on TB molecular diagnostics.
Main Methods:
- Phenotypic susceptibility testing (pDST) for PZA.
- Targeted Sanger sequencing of the pncA gene.
- Whole Genome Sequencing (WGS) using PacBio and IonTorrent platforms.
- Analysis of Sanger sequencing primer regions in relation to WGS findings.
Main Results:
- pDST confirmed PZA-resistant TB.
- Sanger sequencing initially showed wild-type PncA, suggesting PZA-S.
- WGS revealed a large deletion in pncA, confirming PZA-R, and also a deletion within the Sanger sequencing primer region.
- A minority susceptible subpopulation masked the majority resistant population in Sanger sequencing.
Conclusions:
- A minority susceptible subpopulation can obscure a majority resistant population, leading to false susceptibility calls in molecular diagnostics.
- This phenomenon can impact the sensitivity of molecular diagnostics for various drug resistance mutations, not just PZA.
- Development of diagnostics independent of primer region conservation and increased WGS surveillance are crucial for accurate TB diagnosis and treatment.
Related Concept Videos
01:28Pulmonary Tuberculosis V
220
Medical management of tuberculosis (TB) patients involves a comprehensive approach that includes diagnosis, treatment, and monitoring. The specific strategies can vary depending on the type of tuberculosis (latent or active), the patient's overall health status, and other considerations.
Latent tuberculosis infection occurs when TB bacteria are present in a person's body, but are not causing illness or symptoms. It is not contagious, and preventive treatment is crucial to avoid the...
Latent tuberculosis infection occurs when TB bacteria are present in a person's body, but are not causing illness or symptoms. It is not contagious, and preventive treatment is crucial to avoid the...
220
01:26Pulmonary Tuberculosis IV
185
Tuberculosis, more commonly referred to as TB, is an infectious disease stemming from Mycobacterium tuberculosis. While it primarily impacts the lungs, TB can also affect other body areas. Given its severity and global impact, timely and accurate diagnosis is crucial for controlling its spread and improving patient outcomes.
Several diagnostic approaches are used to detect TB. The conventional method is the Tuberculin Skin Test (TST), also known as the Mantoux test. However, this method has...
Several diagnostic approaches are used to detect TB. The conventional method is the Tuberculin Skin Test (TST), also known as the Mantoux test. However, this method has...
185