Evaluation of a low-cost calorimetric approach for rapid detection of tuberculosis and other mycobacteria in culture

Abstract

The objective of this study was to evaluate the effectiveness of microcalorimetry in rapid detection of mycobacterium species using an inexpensive Isothermal microcalorimetry (IMC) instrument. In addition, we compared microcalorimetry with conventional monitoring techniques. Isothermal microcalorimetry measures heat production rate and can provide rapid detection of living mycobacteria in clinical specimens. Using liquid medium showed that bacterial activity measured by IMC using a TAM Air® agreed with the triphenyl tetrazolium chloride (TTC) assay. Using solid medium to enhance growth, fast-growing mycobacteria detection was achieved between 26 and 53 h and slow-growing mycobacteria detection was achieved between 54 and 298 h. In addition, the calorimetric data were analysed to estimate the growth rate and generation time of the mycobacteria monitored. Infections caused by mycobacteria are severe and difficult to treat. With 9·27 million new cases of tuberculosis in 2007, developing countries experience severe health and economic consequences owing to the lack of an affordable, fast detection method. Research-grade IMC instruments are too expensive to use in developing countries. Our study demonstrates that less-expensive instruments such as the TAM air® are adequate for mycobacteria detection and therefore establishes a clear proof of concept.