Comparison of isothermal microcalorimetry and BACTEC MGIT960 for the detection of the metabolic activity of Mycobacterium tuberculosis in sputum samples

Introduction This study explores the uses of microcalorimetry to detect Mycobacterium tuberculosis (TB) in sputum. Microcalorimetry measures metabolic heat evolution during cellular proliferation of tuberculosis (TB) and is considered as a possible alternative to conventional diagnostic tools.Objectives To compare the time to detection (TTD) from the BACTEC (TM) MGIT (TM) 960 and the calScreener (TM) calorimetric system.Methods Sixty-four sputa samples were selected from patients with confirmed pulmonary tuberculosis. Those sample were then decontaminated and analysed using calorimetry and BACTEC MGIT 960 system.Results The incubation period until detection of M. tuberculosis in the sample was 8 center dot 5 +/- 3 center dot 7 days for the MGIT system and 10 center dot 1 +/- 4 center dot 1 days (mean +/- SD) for calorimetry.Conclusions The microincubations in the 48-well format calScreener offers potential for rapid and accurate diagnostic of TB in different samples. Although TTD from calorimetry is still longer than with the MGIT, our findings suggest that several improvements are possible. Still, the instrument is ideal for continuous, real-time analysis of net metabolic heat release of limited sample numbers.Significance and Impact of the Study Our result emphasizes that with further optimization, calorimetry can become an alternative detection method for tuberculosis.