Susceptibility of Mycobacterium intracellulare to hydrogen peroxide

The susceptibility to H2O2 of 5 strains of Mycobacterium intracellular and both catalase-positive (TMC 102) and negative (TMC 303) strains of M. tuberculosis, H37Rv, was tested at pH 7.0 and 4.0. All strains of M. intracellular were significantly more resistant to this oxygen metabolite than were the two M. tuberculosis strains, even though the catalase activity of M. tuberculosis TMC 102 was higher than most M. intracellular strains. Even the catalase negative (Egge-man) strain of M. intracellular showed greater resistance to 0.2% H2O2 than M. tuberculosis H37Rv (TMC 102). This suggests that M. intracellular is protected from H2O2 damage by factors additional to their catalase activity.