[Validity of measuring time to detect growth of M. tbc by BACTEC MGIT960 system for quantitation and prediction of mycobacterial growth].
METHODS
Time to detect growth of M. tbc by BACTEC MGIT960 system was examined in sputum specimens collected from 114 patients with active pulmonary tuberculosis before and during antituberculosis therapy. By measuring TTD under chemotherapy, we tried to quantify mycobacterial growth and determine the sensitivity of MGIT system.


RESULTS
The mean TTD significantly decreased in response to an increment in the range of the quantitation scale for solid media. Moreover, the TTD negatively correlated with colony counts (rho = - 0.636, P < 0.01). When automated monitoring continued until Day 28 after incubation, MGIT system had been capable of detecting 98% of Ogawa-positive specimens. The receiver operating characteristic (ROC) curve was plotted to determine the sensitivity and specificity in MGIT system, indicating the sensitivity of 98.3% corresponding cutoff level for TTD of Day 28.


CONCLUSIONS
Measuring TTD in MGIT system could allow estimating the mycobacterial growth in similarly quantitative manner. The appropriate endpoint of monitoring could be decided as 4 weeks, accurately reflecting an outcome of cultivation with solid media.
Yamamoto
Yasushi
Y
Department of Respiratory Medicine, National Hospital Organization Douhoku National Hospital, 7 Hanasaki, Asahikawa-shi, Hokkaido 070-8644, Japan. yasushiy@asahikawa.hosp.go.jp
Fujiuchi
Satoru
S
Yamazaki
Yasuhiro
Y
Takeda
Akinori
A
Nishigaki
Yutaka
Y
Fujita
Yuka
Y
Fujikane
Toshiaki
T
Shimizu
Tetsuo
T
D000368:Aged; D000995:Antitubercular Agents / Q000627:therapeutic use; D015169:Colony Count, Microbial / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D009169:Mycobacterium tuberculosis / Q000254:growth & development* / Q000302:isolation & purification; D012372:ROC Curve; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology*; D013997:Time Factors; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology*
D000995:Antitubercular Agents