Two Liquid Medium Systems, Mycobacteria Growth Indicator Tube and MB Redox Tube, for Mycobacterium tuberculosis Isolation from Sputum Specimens

Abstract

Two manual liquid medium systems, the Mycobacteria Growth Indicator Tube (MGIT) and MB Redox tube systems, were evaluated in comparison to the radiometric BACTEC-460 semiautomated system for recovery ofMycobacterium tuberculosis from sputum specimens. The highest level of recovery, from a total of 77 culture-positive specimens, occurred with the BACTEC-460 system (92.2%), followed by the MB Redox tube (80.5%) and the MGIT (63.6%) systems. The shortest time to detection was observed also among the cultures in BACTEC-460: a mean of 12 days to a growth index (GI) of 10 and 15 days to a GI of 500. The mean times for the other systems were 16 days for the MB Redox tube system and 17.4 days for the MGIT system. The proportion of cultures grown after more than 3 weeks of incubation was only 2.8 or 8.4% in BACTEC-460 (for a GI of 10 or 500) but 17.7% in MB Redox and 22.5% in MGIT. Despite these differences in comparison to the BACTEC-460 system and some differences between the MGIT and MB Redox tube systems, either of the two manual liquid medium systems presents a reasonable alternative to the BACTEC-460 system, especially for laboratories with a limited workload, and a valuable element in the laboratory protocol, in conjunction with solid media, for obtaining rapid detection of growth from about 80% of culture-positive specimens and for better overall recovery of M. tuberculosis.

Comparison between conventional and recent culture methods for detection of fish mycobacteria

“…These results agree with that reported by Wolf et al (1998), Abe et al (1999), Akos and Pal (1999) and Emmanuelle et al (1999). Also, the present results agreed with the finding of Heifets et al (2000) who recorded that the time for recovery of NTM in MB-Redox tube was 6.9 days for smear positive specimens and 15.5 days for smear negative specimen. They added that neither MB-Redox system nor other recent techniques (MGIT and BACTEC 460) should be used instead of a solid media (L-J medium) rather than they should be used in addition to it, the combined use of MB-Redox with L-J medium improved the overall level of recovery of mycobacteria from the specimens and provides rapid detection of mycobacterial growth for up to 88% of the culture positive specimens.…”

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“…XTT does work well with MAC in 1.5 ml tubes, although microplate format was not examined [44]. MB-Redox is a commercial (heipha Dr. Muller GmbH, Germany) tube-based system using selective Kirchner media containing a tetrazolium dye for detection and susceptibility testing of mycobacteria [45][46][47], but has not yet been examined for compound screening purposes.…”

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“…Radiometric liquid culture systems have been in common use in level III mycobacteriology laboratories in developed countries but the difficulty of working with radioactive materials, the necessity of expensive apparatus for the detection of radioactive gas and the cost of materials limit the use of these systems. Recently, alternative growth detection methods for automated liquid culture employing oxygen pressure detection (TREK/ ESP II System), fluorescence based (Mycobacteria Growth Indicator Tube-MGIT System, BD) [27][28][29] and colorimetric methods of detection of growth (BacT ALERT 3D System, Biomerieux) have been described and commercialized [30]. However, these methods offer an attractive enhancement (not replacement) to culture on Lowenstein-Jensen or other solid media, the cost of these commercial systems is currently very high, precluding their use at the primary health care level.…”