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Heteroresistance in Mycobacterium tuberculosis
H Rinder1, K T Mieskes, T Löscher
1Department of Infectious Diseases and Tropical Medicine, University of Munich, Germany. rinder@lrz.uni-muenchen.de
Summary
Heteroresistance in Mycobacterium tuberculosis is common and can be missed by standard culture methods and some direct genetic tests. Detecting mixed genotypes in clinical samples is crucial for accurate drug resistance prediction.
Area of Science:
- Microbiology
- Genetics
- Infectious Diseases
Background:
- Drug resistance in Mycobacterium tuberculosis is a significant global health challenge.
- Resistance is often associated with specific mutations in key genes.
- Genotypic analysis directly from clinical specimens could expedite resistance prediction.
Purpose of the Study:
- To determine if genotypes detected after Mycobacterium tuberculosis cultivation accurately reflect those in the original clinical sample.
- To investigate the prevalence and impact of heteroresistance in clinical tuberculosis samples.
Main Methods:
- Non-integrative methods, including restriction fragment length polymorphisms and PCR cloning, were used to analyze katG, rpsL, and embB genotypes.
- Genotypic analysis of original clinical samples was compared to phenotypic resistance profiles after cultivation.
Main Results:
- Heteroresistance, characterized by mixed populations of resistant and susceptible genotypes, was detected in nearly 20% of samples.
- Specific genes analyzed included katG, rpsL, and embB, associated with resistance to isoniazid, streptomycin, and ethambutol.
- Direct sequencing, an integrative method, failed to detect heteroresistance in repeated attempts.
Conclusions:
- Heteroresistance is a prevalent and significant phenomenon in clinical tuberculosis.
- Cultivation and some culture-independent methods can obscure the presence of heteroresistance.
- Accurate detection of heteroresistance requires appropriate molecular techniques.