Tuberculosis patients infected with M. tuberculosis strains from a particular mycobacterial lineage are at a higher risk of acquiring drug resistance, reports a study published this week in Nature Genetics.
Sarah Fortune and colleagues compared clinical M. tuberculosis isolates from within Lineage 2, an East Asian mycobacterial lineage that have been associated with increased drug resistance rates to strains from Lineage 4, an Euro-American lineage. They find that the Lineage 2 strains acquired drug resistance faster than the Lineage 4 strains when cultured in the laboratory. To examine the relevance in human infections, they compared the genome sequences of M. tuberculosis strains from a tuberculosis outbreak in British Columbia, Canada, and use this to estimate the in vivo mycobacterial mutation rate for each lineage. Fortune and colleagues next developed a mathematical model to simulate the emergence of drug resistance within a patient, showing a higher risk for the development of multiple drug resistance in patients infected with Lineage 2 strains.