1986 Volume 61 Issue 4 Pages 265-271
In experiments using 4% NaOH solution, it was found that with longer pretreatment time, there was a significant decrease in the survival rates of mycobacteria (M. tubercu losis H37Rv IID 591, M. kansasii P-1, M. scrofulaceum ATCC 19881, M. intracellulare ATCC 15984, M. fortuitum ATCC 6841) (p<0.05, ttest). M. tuberculosis was the most resistant strain to 4% NaOH solution, and M. fortuitum (Runyon group IV) was the most sensitive. The survival rates of them following pretreatment with 1% NaOH solution were higher than the values obtained with 4% NaOH solution. It was considered that pretreatment with 1% NaOH solution for 30 min at 37°C was not only bactericidal to contaminating bacteria but also significantly to mycobacteria, and not so good as for 5 min treatment at room temperature with 4% NaOH solution.
It was clear in this experiment that mycobacteria in sputa were also significantly damaged by pretreatment with 4 and 1% NaOH solutions. It was considered that pretreatment with NaOH solution would be one of the causes of the “smear-positive and culture-negative” phenomenon, so that consequently a misdiagnosis of mycobacteri osis might be made. Therefore, new methods to replace the pretreatment with NaOH solutions should be investigated.
