The susceptibility of strains of Mycobacterium tuberculosis to catalase-mediated peroxidative killing.

At low pH and with continuous low concentrations of hydrogen peroxide generated in situ, catalase was able to replace peroxidase in the peroxidase/hydrogen peroxide/iodide microbicidal system. The system was effective against Escherichia coli and Mycobacterium tuberculosis. Iodide could not be replaced by chloride. The system was effective in lactate buffer, but not in citrate/phosphate buffer. Strains of M. tuberculosis with high and low virulence were equally susceptible. The observations are discussed in the context of an involvement of host-cell catalase in a possible intracellular killing mechanism against M. tuberculosis.