Detection of Mycobacterium tuberculosis growth by direct microscopic observation has a lower cost, higher sensitivity and higher diagnostic value than liquid and solid media cultures.

Background: Culture is needed to confirm tuberculosis but results are generally obtained after several weeks.

Objectives: We compared a direct microscopic observation technique for detection of mycobacterial culture positivity (MODS) with the classic solid and MB/BacT cultures in terms of sensitivity, contamination rate, speed and cost on 488 samples.

Results: The sensitivity of the MODS technique--99,2% (162 positive samples) was higher than MB/BacT 78,4% (125 positive samples) and solid culture 69,6% (113 positive samples) P<0.005 for all comparisons. The median times to positivity were 21, 13.3 and 3 days on solid media, B/BacT and MODS respectively.

Conclusions: The MODS technique is faster and more sensitive than both solid media and MB/BacT culture.