Comparison of rapid in-house methods for drug susceptibility testing of Mycobacterium tuberculosis with the proportion method and MGIT 960 system

MORCILLO N; IMPERIALE B; DI GIULIO B; CHIRICO C; PALOMINO J

Estocolmo

Congreso; 17 Congreso Anual de la Sociedad Europea de Medicina Respiratoria (ERS); 2007

Sociedad Europea de Medicina Respiratoria (ERS)

Multidrug-resistance to anti-tuberculosis agents timely detection is important in the effective management of tuberculosis (TB) cases. This study was designed as a clinical trial to assess the performance of in-house drug-susceptibility testing for antimicrobial susceptibility of M. tuberculosis complex. The assessed methods for isoniazid (INH), streptomycin (SM), rifampicin (RIF), ethambutol and levofloxacin (LX) were: the microplate colorimetric-based methods using MTT and resarzurin, and the nitrate reductase assay only for RIF. Results from 492 clinical isolates were compared with those from MGIT960 and the indirect proportion method on LJ medium (ILJ) as gold standards (GS).  Novel methods results were available in an average of 8 days with good correlation among their results and those from the GS. The higher sensitivity and specificity was observed with RIF, INH and LX. Colorimetric methods were performed in a suitable microplate format that could be easily standardized for its use in clinical laboratories. The global performance ranged 0.99 to 0.97 (95% CI: 0.97-1.00) for all the tested methods and drugs. The cost of 1 drug MIC determination was U$S 0.83. The general performance of these methods as well as the low-cost and no necessity of expensive equipment would support their inclusion in clinical laboratories.