Predominance of Beijing genotype in extensively drug resistant Mycobacterium tuberculosis isolates from a tertiary care hospital in New Delhi, India

ABSTRACT

Out of a total of 311 Mycobacterium tuberculosis isolates from sputum specimens subjected to first- and second-line drug-susceptibility testing [DST] at a hospital serving as a referral center for chronic tuberculosis [TB] cases in New Delhi, 232/311 [74.6%] isolates were found to be resistant to isoniazid and rifampicin. Among multidrug-resistant [MDR] isolates, 119/232 [51.3%] were resistant to four first-line drugs [streptomycin, isoniazid, rifampicin and ethambutol]. Mono-resistance to isoniazid was observed in 18 [5.7%] isolates, while none of the isolates tested showed mono-resistance to rifampicin. 50/232 [21.5%] isolates met the definition of extensively drug resistant [XDR] TB, i.e., additional resistance to a fluoroquinolone and at least one of the three injectable second-line drugs kanamycin, capreomycin, or amikacin. Spoligotyping of the XDR-TB isolates revealed 14 patterns; 39/50 [78%] isolates being grouped in three clusters vs. 11/50 [22%] isolates being unique. SIT1/Beijing represented the largest cluster [n = 21, 42%], followed by SIT26/CAS1-Delhi [n = 10, 20%] and SIT 53/T1 [n = 8 isolates; 16%]. This study corroborates recent observations from North India suggesting that both Beijing and CAS1-Delhi lineages constitute the bulk of XDR-TB isolates that are disseminating rapidly across a large geographical region in and around the capital city of India