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[Clinical interest of a new simple system for isolating Mycobacterium tuberculosis]
M Casal1, J Gutiérrez, M Vaquero
1Servicio de Microbiología, Facultad de Medicina, Hospital Universitario Reina Sofía, Córdoba.
Background:
A new system, Mycobacteria Growth Indicator Tube (MGIT), was used for the recovery of M. tuberculosis from clinical specimens, which was compared with conventional methods of microbiological methods. The MGIT system consists of tubes containing liquid medium and a fluorescent oxygen consumption sensor to detect bacterial growth.
Methods:
A total of 197 clinical specimens from 162 patients with clinical suspicion of tuberculosis were processed in parallel and seeded in the new system, the radiometric system BACTEC and Löwenstein.
Results:
The validity criteria for the new system were: sensitivity, 95.4%; specificity, 100%; negative predictive value, 89.3%, and positive predictive value, 100%. The greatest clinical agreement occurred with MGIT and BACTEC. The mean time up to diagnosis of M. tuberculosis recovered from patients was 11 days (range: 7-13 days). No significant differences were found regarding contamination of respiratory samples in the three systems.
Conclusion:
Given the simplicity of utilization of the new system-which does not require radioactive compounds- and the results, the MGIT system appears as an easy-to-use new method, which yields results in a short time, with a good sensitivity in detecting Mycobacterium tuberculosis from clinical specimens from suspected patients with tuberculosis.