Strain diversity drives heterogeneous responses to tuberculosis combination therapy

Area of Science:

• Microbiology
• Drug Discovery
• Genomics

Background:

• Strain diversity in Mycobacterium tuberculosis (Mtb) influences clinical outcomes.
• Understanding drug susceptibility phenotypes of clinical isolates is crucial.
• Limited knowledge exists on drug response patterns in diverse Mtb strains.

Purpose of the Study:

• To identify drug response patterns in phylogenetically diverse Mtb clinical isolates.
• To evaluate phenotypic responses to single-drug and combination therapies.
• To understand how strain variation affects drug efficacy.

Main Methods:

• Selected 13 diverse Mtb clinical strains and one reference strain.
• Tested 10 antibiotics in single, pair, and three-way combinations.
• Assessed responses in standard and cholesterol-rich media using normalized growth rate inhibition (GRmax).

Main Results:

• Mtb strains showed varied drug response phenotypes across 65 combinations and two conditions.
• Effective drug pairs differed by strain and metabolic environment.
• Strain drug sensitivity correlated with combination treatment sensitivity.
• Genetic relatedness, not just distance, drove variation in drug response.

Conclusions:

• Preclinical studies should select Mtb strains based on drug response phenotypes, not solely genetic diversity.
• Combination therapy effectiveness depends on infecting strain and metabolic niche.
• Understanding strain-specific drug responses is key for optimizing treatment strategies.