Objectives: We compared the BBL Mycoprep (Becton Dickinson Japan) and home-made 2%NaOH decontamination procedures by using an equal amount of expectorated sputum in the aerosol-free 30 ml KT centrifuge tube with the rugged inner surface.
Method: A total of 113 sputum specimens obtained in NHO Kinki-Chuo Chest Medical Center in November 2004 were subjected to two decontamination methods. All specimens were divided into two equal portions after concentrating the sediments processed by semi-kaline protease (SAP), then decontaminated, and inoculated into MGIT. The tubes were incubated at 37 degrees C and monitored for up to forty-second days.
Results: Comparing these decontamination procedures, the time of the recovery of mycobacteria strains in the 2%NaOH (mean 8 days) was significantly faster than in the BBL Mycoprep (mean 11 days). Of these, 19 specimens (16.9%) processed by the BBL Mycoprep were positive for growth of mycobacteria, and similarly 18 specimens (16.0%) processed by the 2%NaOH (p>0.5) were positive. The 19 mycobacteria recovered by the BBL Mycoprep were identified as 14 M. tuberculosis strains and 5 NTM strains. The decontamination rate was 0.9% in 2%NaOH and 6.2% in Mycoprep, however the difference was statistically not significant (p>0.5).
Discussion: We verified that the 2%NaOH was an alternative method suitable for the digestion and decontamination procedure, and 2%NaOH was useful for the isolation and detection of mycobacteria as well.