A B S T R A C TRapid detection of drug resistance in Mycobacterium tuberculosis is important for the successful treatment of tuberculosis. Fluoroquinolone and aminoglycoside resistance detection by molecular methods becomes more complex due to cross resistance among them. Thus, we aimed to determine cross-resistance and mutations in resistance genes for these drugs. A total of 336 multidrug-resistant tuberculosis (MDR-TB) cases received in Mycobacteriology laboratory were screened for phenotypic drug sensitivity testing for second-line drugs, i.e., ofloxacin, amikacin, kanamycin, and capreomycin. Molecular characterization of resistance was done by DNA sequencing of gyrA gene for fluoroquinolones (FQ), and multiplex allele-specific polymerase chain reaction (PCR) and PCR restriction fragment length polymorphism (RFLP) of rrs gene for aminoglycosides. Of 336 MDR-TB isolates, 12 were extensively drug-resistant tuberculosis and 219 were sensitive to all the drugs tested. Ofloxacin, amikacin, kanamycin, and capreomycin resistance was detected in 101 (30.1%), 23 (6.8%), 27 (8.1%), and 19 (5.6%) cases, respectively. Eight different mutations were detected in gyrA gene in ofloxacin-resistant isolates and A1401G nucleotide change in rrs gene were seen in 55.6% (15/27), 65.2% (15/23), and 68.4% (13/29) for kanamycin-, amikacin-, and capreomycin-resistant isolates, respectively. Information on second-line drug resistance-associated mutations could potentially be used for development of newer rapid diagnostic tests.

Emergence of Tuberculosis and Multi drug resistance tuberculosis at higher pace in the population needs rapid diagnosis with accuracy to reduce the transmission of disease and suffering of the patients. The technique of GenexpertMTb/Rif by Cepheid rolled out by WHO has given high support to the humanity by rapid and accurate detection of Tuberculosis and resistance to rifampicin. The technique has less turnaround time, can be performed in simple lab settings, fully automated processing and result interpretation and the professional needs a hands on training of less than thirty minutes as compared to other sophisticated techniques for TB and drug resistance diagnosis. The article here discussed the role of CBNAAT in different groups of patients with accordance to the researches already published in support of high and promising performance of GenexpertMTb.

Tuberculosis is one of the most ancient infectious diseases known to mankind. Detection of the causative organism, Mycobacterium tuberculosis, has experienced a series of advances from the late 19th century through early 21st century. The hierarchy of diagnosis ranges from smear microscopy with traditional Ziehl–Neelsen staining to advanced light-emitting diode–fluorescence microscopy staining to both solid and liquid culture, and more recently, to genotypic methods like nucleic acid amplification. Each procedure has its own merits and drawbacks in terms of specificity, sensitivity, minimum detectible number of bacilli, and most crucially, turnover time. The latest diagnostic tools, like geneXpert and line probe assays, have gone a step further by detecting drug resistance. Both early and accurate diagnosis based on the drug susceptibility test implies precise and prompt initiation of treatment, thereby curtailing not only the agony of patient but also the burden tuberculosis places on the health system.