European Society of Mycobacteriology - Instituto Nacional de Saúde ...

PP-38
RAPID DETECTION OF EXTENSIVELY DRUG-RESISTANT Mycobacterium
tuberculosis BY THE RESAZURIN MICROTITER ASSAY PLATE
Paasch, Fabienne; Martin, Anandi; Docx, Sven; Fissette, Kristina; Portaels, Françoise; Palomino, Juan Carlos
Institute of Tropical Medicine, Antwerp, Belgium
Introduction
A major concern for tuberculosis control programs is the emergence of multidrug-resistant (MDR) tuberculosis and
especially extensively drug-resistant (XDR) tuberculosis. Conventional drug susceptibility testing (DST) requires 3 to 6
weeks to yield results. Therefore, there is an urgent need of new timely and accurate detection of first and second line
anti-tuberculosis drug resistance.
Purpose of the study
The aim of this study was to evaluate the first and second line drugs rifampicin (RIF), isoniazid (INH), ofloxacin
(OFX), kanamycin (KAN), amikacin (AMK) and capreomycin (CAP) with clinical isolates of M. tuberculosis by
the colorimetric resazurin microtiter assay (REMA) plate in comparison to the indirect proportion method (PM).
Method
A total of 150 clinical isolates were studied. DST by PM was performed on Löwenstein Jensen for RIF and INH and on
7H11 agar for the other drugs. The minimal inhibitory concentration obtained by REMA was compared with the PM.
Results
REMA results were easily determined visually after 8 days compared to 21 to 42 days by the PM. Out of 150 isolates 92
were MDR and 20 were XDR. After defining the critical concentration for each drug by the colorimetric assay, excellent
results were obtained for first and second line drugs with levels of specificity and sensitivity between 93% and 100%.
Conclusion
In this study drug resistance detection by REMA has shown high level of agreement with the conventional PM. Therefore,
REMA could be a reliable alternative method for rapid detection of MDR and XDR M. tuberculosis.
110 ESM 2009