INT J TUBERC LUNG DIS 19(4):434–439 Q 2015 The Union http://dx.doi.org/10.5588/ijtld.14.0596 Genetic mutations associated with rifampicin and isoniazid resistance in MDR-TB patients in North-West India P. Kumar, P. Kumar, V. Balooni, S. Singh Division of Clinical Microbiology and Molecular Medicine, Department of Laboratory Medicine, All India Institute of Medical Sciences, New Delhi, India SUMMARY BACKGROUND: Effective tuberculosis (TB) control has been hindered by the emergence of multidrug-resistant TB (MDR-TB). OBJECTIVE: To analyse the frequency of drug resis- tance among presumed cases of drug-resistant TB in the state of Punjab, India, and to determine the frequency of various genetic mutations detected using the line-probe assay (LPA). METHODS: Eight hundred patients with presumptive drug-resistant TB were enrolled under the programmatic management of drug-resistant TB under India’s Revised National Tuberculosis Control Programme. Sputum samples from these patients were subjected to smear microscopy and LPA. Clinicodemographic details along with drug resistance patterns and genetic mutations were studied. RESULTS: After excluding non-eligible samples, 545 samples were analysed, of which 290 (53.2%) showed resistance. Isoniazid and rifampicin (RMP) monoresist- ance were detected in respectively 9.3% (51/545) and 18% (98/545) of samples, while MDR was present in 25.8% (141/545) of samples. Of the MDR-TB cases, 2.1% (3/141) were treatment-na¨ ıve, while 90.8% (128/ 141) were on retreatment. The most common mutation conferring RMP resistance was S531L. CONCLUSION: All patients undergoing retreatment for TB should be tested for drug susceptibility at the initial evaluation. Factors responsible for high MDR- TB and heteroresistance in Punjab need further studies. KEY WORDS: drug-resistant tuberculosis; Punjab; genetic mutations; LPA; MTBDRplus TUBERCULOSIS (TB) remains a major public health problem, particularly in developing countries. India alone accounts for 26% of global TB cases. 1 Worldwide, 3.6% of new TB cases and 20.2% of previously treated cases are estimated to have multidrug-resistant (MDR) TB, defined as resistance to rifampicin (RMP) and isoniazid (INH). India has one of the world’s highest burdens of drug-resistant TB. The risk of developing extensively drug-resistant TB (XDR-TB) is higher in MDR-TB strains. The emergence of MDR- and XDR-TB points towards the urgent need for proper identification of Mycobacte- rium tuberculosis with drug susceptibility testing (DST) to achieve effective management. 2 According to the new initiative of the Revised National Tuberculosis Control Programme (RNTCP) known as programmatic management of drug-resis- tant TB (PMDT), DST should be performed for all smear-positive retreatment cases at diagnosis and for all new cases who are smear-positive after completion of first-line anti-tuberculosis treatment. 3 The emer- gence of MDR-TB is mainly due to non-adherence to treatment. 4 A high prevalence of MDR-TB (27.6%) was observed among patients who had previously undergone anti-tuberculosis treatment in Chandi- garh, India; 5 all patients undergoing retreatment should therefore undergo DST at initiation of treatment. In addition, measures should be taken to promote drug adherence. 3 As delays in obtaining DST results may contribute to the transmission of drug- resistant TB and the amplification of drug resistance, early diagnosis of drug-resistant TB is an urgent clinical priority. However, widespread implementa- tion of liquid culture-based DST may be challenging in developing countries due to financial, infrastruc- ture and human resource requirements. 6 The World Health Organization (WHO) therefore recommends the use of molecular line-probe assays (LPAs) for rapid screening for MDR-TB in low- and middle- income settings. 7 Molecular assays can be performed directly on smear-positive sputum samples, and provide results in 1–2 days. The most widely used test is the GenoType w MTBDRplus (Hain Lifesciences, Nehren, Germany) Correspondence to: Sarman Singh, Division of Clinical Microbiology and Molecular Medicine, All India Institute of Medical Sciences, Ansari Nagar East, Gautam Nagar, New Delhi 110 029, India. Tel: ( þ 91) 11 2658 8484. Fax: ( þ 91) 11 2658 8663/ 2658 8641. e-mail: sarman_singh@yahoo.com Article submitted 10 August 2014. Final version accepted 8 December 2014.