QUANTIFICATION OF AIRBORNE MYCOBACTERIUM TUBERCULOSIS IN HEALTH CARE SETTING USING REAL-TIME QPCR COUPLED TO AN AIR-SAMPLING FILTER METHOD

Mycobacterium tuberculosis infection remains one of the major public health issues worldwide. Current qualitative assays (only positive or negative results) do not provide comprehensive information regarding health risk of M. tuberculosis. This study attempted to develop a quantitative assay to measure air concentration of M. tuberculosis in a health care setting. A total of 22 air samples were taken from the negative pressure isolation rooms of tuberculosis patients. The air was filtered through a Nuclepore filter with sampling time of 8 h. The DNA of M. tuberculosisin these airborne samples was then analyzed by the ABI 7700 real-time quantitative polymerase chain reaction (real-time qPCR) system. The real-time qPCR method could perform measurements of counts in a dynamic range of over 6 orders with a high sensitivity. The measured M. tuberculosis concentrations varied widely, from 1.43 ? 10 copies/m3 to 2. 06 ? 105 copies/m3. Comparisons among airborne M. tuberculosis levels, sputum smear, results, and sputum culture results showed moderate correlations. The filter/ real-time qPCR method proved extremely sensitive and rapid for quantifying airborne M. tuberculosis. In addition, it is a powerful sampling tool that has potential applications as an investigational device, which might be valuable in conducting studies that validate the efficacy of engineering controls and work practices.