Estimation of second line anti-tubercular drug susceptibility to Mycobacterium tuberculosis in clinical isolates

Tuberculosis (TB) is an infectious disease that is among the most common in the world and is a leading cause of high mortality and morbidity. In India, there is very limited data on second line drug susceptibility testing. The aim of the study was to find out the prevalence of Multi Drug Resistant (MDR) isolates among Mycobacterium tuberculosis (MTB) complex strains and to assess the sensitivity pattern to four commonly used 2^nd line anti-tubercular drugs irrespective of their MDR status.

A 61 culture-positive strains of the tuberculosis complex (smear positive or negative) in Mycobacterium Growth Indicator Tube (MGIT) and Lowenstein Jensen (LJ) from various clinical samples were included. We performed MGIT 1^st and 2^nd line susceptibility testing for tuberculosis.

Among the 61 isolates, 12 (19.6%) were multi drug resistant. Capreomycin resistance was observed in 17 (27.8%) isolates, kanamycin resistance in 30 (49.1%), ofloxacin resistance in 5 (8.1%), and ethionamide resistance in 6 (9.8%) isolates. Resistance to kanamycin and ethionamide was more common among patients with multi drug resistant tuberculosis (MDR-TB) than among those with non-MDR-TB.

The MGIT system has surpassed solid culture and is an excellent method for performing culture and drug sensitivity testing for tuberculosis. However, its use remains limited by economic and logistical challenges. The high prevalence of aminoglycoside resistance suggests the need to preserve these drugs for treating patients with MDR-TB.