Bactericidal effects of 4% and 1% NaOH solution on a variety of mycobacteria (reference strains) suspended in saline were examined at various intervals (1, 5, 10 and 30 minutes) after the suspension. The bactericidal effect was evaluated by the survival rate (Mean±S.E.) in com parison with the control.
The results obtained were as follows. After the pretreatment for 5 minutes with 4% and 1% NaOH solution, the survival rates of Mycobacterium tuberculosis H37Rv (IID 591) were 63±8% and 74±4%, respectively. Those of M. kansasii (p1.) were 35±12% and 43±8%, of M. scrofulaceum (ATCC 19881) were 29±10% and 32±10%, of M. intracellulare (ATCC 15984) were 16±4% and 12±6%, and of M. fortuitum (ATCC 6841) were 1% and 17±4%, respectively. After the pre treatment for 30 minutes with 4% and 1% NaOH solution, the survival rates of M. tuberculosis H37Rv were 45±3% and 55±8%, of M. kansasii were 18±6% and 7±4%, of M. scrofulaceum were 16±6% and 10±6%, of M. intracelluare were 11±3% and 8±6%, and of M. fortuitum were 0% and 4±2%, respectively.
The longer the pretreatment time with both concentrations of NaOH, the lower the survival rates of all mycobacteria. Moreover, there were marked differences in the resistance to NaOH among the species of atypical mycobacteria and it was demonstrated that M. fortuitum was damaged most markedly by the treatment with NaOH solution. In this experiment, M. fortui turn could not grow on Ogawa egg media after the treatment with 4% NaOH for 10 minutes.
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