Direct detection of Mycobacterium tuberculosis in clinical samples by a dry methyl green loop-mediated isothermal amplification (LAMP) method.

The purpose of this study was to develop a simple visual methyl green (MeG) based dry loop-mediated isothermal amplification (LAMP) method for early detection of Mycobacterium tuberculosis (MTB) from clinical samples. We identified MeG as an indicator of a positive LAMP reaction, where a positive reaction gave a blue-green color while a negative reaction was colorless. The MeG MTB-LAMP system was further simplified by drying all reagents for ease of use, and was then validated for its ability to diagnose TB directly using Nepalese clinical samples. We evaluated the dry MeG MTB-LAMP with 69 new TB suspected samples from patients that did not have a confirmed history of TB treatment and found the sensitivity in culture positive samples as 92.8% (13/14) and specificity in culture negative samples as 96.3% (53/55). Our LAMP system has the potential to be a point of care test for early diagnosis of active TB in developing countries.