Pyrazinamide susceptibility testing in Mycobacterium tuberculosis using the fast resazurin microtiter assay plate
OBJECTIVE: To evaluate the performance of the resazurin microtiter assay (REMA) plate at pH 5.5 in detecting Mycobacterium tuberculosis susceptibility to pyrazinamide (PZA).
DESIGN: The minimal inhibitory concentration (MIC) of PZA in M. tuberculosis H37Rv and M. bovis AN5 reference strains and in 34 clinical M. tuberculosis isolates (26 PZA-susceptible and eight PZA-resistant) was determined using REMA at pH 5.5 and compared to REMA at pH 6.0.
RESULTS: REMA at pH 5.5 was helpful in discriminating PZA-susceptible from resistant M. tuberculosis isolates when 50 μg/ml PZA was considered as the cut-off for PZA susceptibility. Furthermore, it provided results in 8 days. However, two PZA-resistant isolates failed to grow at pH 5.5.
CONCLUSION: As the REMA method is rapid, inexpensive, easy to perform and read, it would be of great usefulness in low-income countries for detecting PZA-resistant M. tuberculosis. REMA at pH 5.6–5.9 should be evaluated on an extended panel of clinical M. tuberculosis isolates with a greater range of MIC values in different laboratories for a better understanding of its utility in differentiating PZA-resistant from PZA-susceptible isolates.
Document Type: Research Article
Affiliations: 1: Post-Graduate Programme in Health Sciences, State University of Maringá, Maringá, Brazil 2: Department of Clinical Analyses and Biomedicine, State University of Maringá, Maringá, Paraná, Brazil 3: School of Pharmaceutical Science, São Paulo State University, Araraquara, São Paulo, São Paulo, Brazil
Publication date: 2016-11-01
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