Efficacy of Isoniazid Therapy in Mice with Different Genetic Susceptibility to Infection

The question about possible influence of genetic susceptibility to Tuberculosis (TB) infection on the efficacy of its antibiotic treatment remains unanswered, and the results of scarce studies on the topic look contradictory. In the present work we studied the efficacy of short-term INH therapy against M. tuberculosis in hyper-susceptible I/St, relatively resistant BALB/c and highly resistant (I/St x BALB/c) F1 mice by comparing lung and spleen CFU counts and lung histopathology after 1- and 2-mo therapy. Our results indicate that the efficacy of INH therapy, as evaluated at the early phase of infection, is more effective in genetically susceptible hosts. Possible reasons for contradictions between studies applying early VS. late evaluation of the efficacy of treatment are discussed.