Persistence, not resistance, is the cause of loss of isoniazid effect.

摘要

To the Editor-We read with interest the recent report by Gumbo et al., in which a hollow-fiber model was used to study the kinetics of killing of Mycobacterium tuberculosis H37Ra by isoniazid . The main finding was 'that killing ceased after 3-4 days because of the emergence of resistant mutants. From this, the authors concluded that the "age-old" hypothesis that killing by isoniazid in vivo ceases because of depletion of log-phase bacilli is incorrect.The observation that resistance to isoniazid emerges rapidly in vitro is not a new one. In 1999, we described a model to study phenotypic drug tolerance in M. tuberculosis by adding drugs to Bactec radiometric cultures and monitoring the rate of decline of growth indices .