Rifampicin-resistant Mycobacterium tuberculosis: Susceptibility to isoniazid and other anti-tuberculosis drugs
ABSTRACT Based on data from 14 Supranational Tuberculosis (TB) Reference Laboratories worldwide, the proportion of rifampicin (RMP) resistant isolates that were isoniazid (INH) susceptible by phenotypic drug susceptibility testing varied widely (0.5-11.6%). RMP-resistant isolates that were INH-susceptible had significantly lower rates of resistance to other first- and second-line anti-tuberculosis drugs (except rifabutin) compared to multidrug-resistant isolates. RMP resistance is not always a good proxy for a presumptive diagnosis of multidrug-resistant TB, which has implications for use of molecular assays that identify only RMP resistance-associated DNA mutations.
Article: Xpert MTB/RIF test for tuberculosisThe Lancet 08/2011; 378(9790):481-2; author reply 482-3. DOI:10.1016/S0140-6736(11)61243-9 · 45.22 Impact Factor
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ABSTRACT: Tuberculosis takes a heavy toll of ~5000 lives every day from the disease; responsible for the 86% of DALY burden. Despite having drugs to treat TB efficiently, we have failed to control the disease. Mycobacterium tuberculosis has exploited it to their advantage evolving with multiple mutations making it resistant to first-line and second-line drugs. Most of the high-burden countries are low-medium income countries, their national TB program (NTP) still use sputum smear microscopy as the tool of diagnosis. Many new molecular tools are emerging, but confuse the larger TB clinical scientific community at the NTPs. Coherent information need to be disseminated, encouraging TB scientific community to generate evidences within NTPs assessing new tools through critical analyses in terms of value addition and cost benefit before considering rolling out in the program. It is also imperative that the scientific community need to have an open mind to use different tools in the right permutation and combination than being exclusive of one another. This article portrays an overview of the diagnostics landscape in 2012 with pros and cons of different tools to be able to generate a step-wise algorithm for optimal exploitation of the tools within available resources in each of the settings.European Journal of Microbiology and Immunology 12/2012; 2(4):275-281. DOI:10.1556/EuJMI.2.2012.4.5
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ABSTRACT: The purpose of this study was to assess the performance of Cepheid® Xpert MTB/RIF® ("Xpert") and TB-Biochip® MDR ("TB-Biochip"). Sputum specimens from adults with presumptive tuberculosis (TB) were homogenized and split for: (1) direct Xpert and microscopy, and (2) concentration for Xpert, microscopy, culture [Lowenstein-Jensen (LJ) solid media and Mycobacteria Growth Indicator Tube® (MGIT)], indirect drug susceptibility testing (DST) using the absolute concentration method and MGIT, and TB-Biochip. In total, 109 of 238 (45.8 %) specimens were culture-positive for Mycobacterium tuberculosis complex (MTBC), and, of these, 67 isolates were rifampicin resistant (RIF-R) by phenotypic DST and 64/67 (95.5 %) were isoniazid resistant (INH-R). Compared to culture of the same specimen, a single direct Xpert was more sensitive for detecting MTBC [95.3 %, 95 % confidence interval (CI), 90.0-98.3 %] than direct (59.6 %, 95 % CI, 50.2-68.5 %) or concentrated smear (85.3 %, 95 % CI, 77.7-91.1 %) or LJ culture (80.8 %, 95 % CI, 72.4-87.5 %); the specificity was 86.0 % (95 % CI, 78.9-91.3 %). Compared with MGIT DST, Xpert correctly identified 98.2 % (95 % CI, 91.5-99.9 %) of RIF-R and 95.5 % (95 % CI, 85.8-99.2 %) of RIF-susceptible (RIF-S) specimens. In a subset of 104 specimens, the sensitivity of TB-Biochip for MTBC detection compared to culture was 97.3 % (95 % CI, 91.0-99.5 %); the specificity was 78.1 % (95 % CI, 61.5-89.9 %). TB-Biochip correctly identified 100 % (95 % CI, 94.2-100 %) of RIF-R, 94.7 % (95 % CI, 76.7-99.7 %) of RIF-S, 98.2 % (95 % CI, 91.4-99.9 %) of INH-R, and 78.6 % (95 % CI, 52.1-94.2 %) of INH-S specimens compared to MGIT DST. Xpert and Biochip were similar in accuracy for detecting MTBC and RIF resistance compared to conventional culture methods.European Journal of Clinical Microbiology 12/2012; 32(6). DOI:10.1007/s10096-012-1798-0 · 2.67 Impact Factor