[Fast identification of mycobacteria in microtiter liquid culture]

This research was to establish a method for fast identification of mycobacteria in microtiter liquid culture and to evaluate its clinical value.

2-thiophenecarboxylic acid hydrazide (TCH) and paranitrobenzoic acid (PNB) at different concentrations were added into liquid culture in 96-well plate. Different mycobacterium standard strains were incubated in liquid culture with PNB and TCH for 7 to 10 days. According to the growth assay for 15 mycobacterium strains and 30 mycobacterium tuberculosis strains, the best PNB and TCH concentration were determined. A total of 424 clinical mycobacterium isolates were identified by microtiter liquid culture at the best PNB and TCH concentration. The results of microtiter liquid culture were compared with those of PCR and DNA sequencing.

The best concentration of PNB was 200 µg/ml in microtiter liquid culture. Compared with the results of PCR, the sensitivity and specificity for identification of mycobacterium tuberculosis complex in microtiter liquid culture were 97.8% (306/313) and 100.0% (107/107) respectively and those for non-tuberculosis mycobacteria in microtiter liquid culture were 100.0% (107/107) and 96.5% (306/317) respectively. The best concentration of TCH was 0.5 µg/ml. Compared with the results of PCR, the sensitivity of mycobacterium tuberculosis in microtiter liquid culture was 100.0% (305/305). The specificity remained under and more studies were needed.

In microtiter liquid culture with PNB and TCH, mycobacteria can be identified in 7 to 10 days. The results were accurate and the process was simple without expensive equipments. This method meets clinical needs and can be used in all level hospitals in China.