Drug resistance among extrapulmonary TB patients: Six years experience from a supranational reference laboratory

There is limited information available about the drug resistance patterns in extrapulmonary tuberculosis (EPTB), especially from high burden countries. This may be due to difficulty in obtaining extrapulmonary specimens and limited facilities for drug susceptibility testing. This study was undertaken to review and report the first and second-line anti-TB drug susceptibility patterns in extrapulmonary specimens received at the National Institute for Research in Tuberculosis (NIRT), Chennai, India, between 2005 and 2012.

Extrapulmonary specimens received from referring hospitals were decontaminated and cultured using standard procedures. Drug susceptibility testing (DST) for Mycobacterium tuberculosis was done by absolute concentration or resistance ratio methods for the first and the second line anti-TB drugs.

Between 2005 and 2012, of the 1295 extrapulmonary specimens, 189 grew M. tuberculosis, 37 (19%) cases were multidrug resistant (MDR) while one was extensively drug resistant (XDR). Specimen-wise MDR prevalence was found to be: CSF-10 per cent, urine-6 per cent, fluids and aspirates-27 per cent, pus-23 per cent, lymph nodes-19 per cent. Resistance to isoniazid and ethionamide was found to be high (31 and 38%, respectively).

Drug resistance including MDR-TB was observed in a significant proportion of extrapulmonary specimens referred for DST. Access to culture and DST for extrapulmonary specimens should be expanded. Guidelines for MDR-TB management should have explicit sections on extra-pulmonary tuberculosis and training on laboratory techniques is urgently required.