Rapid detection of drug resistance and mutational patterns of extensively drug-resistant strains by a novel GenoType® MTBDRsl assay.

BACKGROUND: The emergence of extensively drug-resistant tuberculosis (XDR-TB) is a major concern in the India. The burden of XDR-TB is increasing due to inadequate monitoring, lack of proper diagnosis, and treatment. The GenoType ® Mycobacterium tuberculosis drug resistance second line (MTBDRsl) assay is a novel line probe assay used for the rapid detection of mutational patterns conferring resistance to XDR-TB. AIM: The aim of this study was to study the rapid detection of drug resistance and mutational patterns of the XDR-TB by a novel GenoType ® MTBDRsl assay. MATERIALS AND METHODS: We evaluated 98 multidrug-resistant (MDR) M. tuberculosis isolates for second line drugs susceptibility testing by 1% proportion method (BacT/ALERT 3D system) and GenoType ® MTBDRsl assay for rapid detection of conferring drug resistance to XDR-TB. RESULTS: A total of seven (17.4%) were identified as XDR-TB by using standard phenotypic method. The concordance between phenotypic and GenoType ® MTBDRsl assay was 91.7-100% for different antibiotics. The sensitivity and specificity of the MTBDRsl assay were 100% and 100% for aminoglycosides; 100% and 100% for fluoroquinolones; 91.7% and 100% for ethambutol. The most frequent mutations and patterns were gyrA MUT1 (A90V) in seven (41.2%) and gyrA + WT1-3 + MUT1 in four (23.5%); rrs MUT1 (A1401G) in 11 (64.7%), and rrs WT1-2 + MUT1 in eight (47.1%); and embB MUT1B (M306V) in 11 (64.7%) strains. CONCLUSIONS: These data suggest that the GenoType ® MTBDRsl assay is rapid, novel test for detection of resistance to second line anti-tubercular drugs. This assay provides additional information about the frequency and mutational patterns responsible for XDR-TB resistance.

Use of GenoType® MTBDRplus assay to assess drug resistance and mutation patterns of multidrug-resistant tuberculosis isolates in northern India.

PURPOSE: The emergence and spread of multidrug-resistant tuberculosis (MDR-TB) is a major public health problem. The diagnosis of MDR-TB is of paramount importance in establishing appropriate clinical management and infection control measures. The aim of this study was to evaluate drug resistance and mutational patterns in clinical isolates MDR-TB by GenoType® MTBDRplus assay. MATERIAL AND METHODS: A total of 350 non-repeated sputum specimens were collected from highly suspected drug-resistant pulmonary tuberculosis (PTB) cases; which were processed by microscopy, culture, differentiation and first line drug susceptibility testing (DST) using BacT/ALERT 3D system. RESULTS: Among a total of 125 mycobacterium tuberculosis complex (MTBC) strains, readable results were obtained from 120 (96%) strains by GenoType® MTBDRplus assay. Only 45 MDR-TB isolates were analysed for the performance, frequency and mutational patterns by GenoType® MTBDRplus assay. The sensitivity of the GenoType® MDRTBplus assay for detecting individual resistance to rifampicin (RIF), isoniazid (INH) and multidrug resistance was found to be 95.8%, 96.3% and 97.7%, respectively. Mutation in codon S531L of the rpoB gene and codon S315T1 of katG genes were dominated in MDR-TB strains, respectively (P < 0.05). CONCLUSIONS: The GenoType® MTBDRplus assay is highly sensitive with short turnaround times and a rapid test for the detection of the most common mutations conferring resistance in MDR-TB strains that can readily be included in a routine laboratory workflow.

Changing patterns and trends of multidrug-resistant tuberculosis at referral centre in Northern India: a 4-year experience.

PURPOSE: India has a high burden of drug-resistant tuberculosis (TB), although there is little data on multidrug-resistant tuberculosis (MDR-TB). Although MDR-TB has existed for long time in India, very few diagnostic laboratories are well-equipped to test drug sensitivity. The objectives of this study were to determine the prevalence of MDR-TB, first-line drug resistance patterns and its changing trends in northern India in the 4 years. MATERIALS AND METHODS: This was a prospective study from July 2007 to December 2010. Microscopy, culture by Bactec460 and p-nitro-α-acetylamino-ß-hydroxypropiophenone (NAP) test was performed to isolate and identify Mycobacterium tuberculosis (M. tb) complex (MTBC). Drug sensitivity testing (DST) was performed by 1% proportional method (Bactec460) for four drugs: Rifampicin, isoniazid, ethambutol and streptomycin. Various clinical and demographical profiles were evaluated to analyse risk factors for development of drug resistance. RESULTS: We found the overall prevalence rate of MDR-TB to be 38.8%, increasing from 36.4% in 2007 to 40.8% in 2010. we found that the prevalence of MDR-TB in new and previously treated cases was 29.1% and 43.3% ( P < 0.05; CI 95%). The increasing trend of MDR-TB was more likely in pulmonary TB when compared with extra-pulmonary TB ( P < 0.05; CI 95%). CONCLUSIONS: we found a high prevalence (38.8%) of MDR-TB both in new cases (29.1%) and previously treated cases (43.3%).This study strongly highlights the need to make strategies for testing, surveillance, monitoring and management of such drug-resistant cases.