Actinomycetes from high altitude salt lake Tso-Kar of Ladakh offers bright prospects for antimycobacterial drug discovery especially for drug resistant mycobacteria.

Abstract

The rise of multidrug-resistant (MDR) strains of Mycobacterium tuberculosis (M. tb) has driven the search for new antimycobacterial agents. Our study focused on isolation and characterization of actinomycetes from the hypersaline Tso-Kar Salt lake in Ladakh, India, to explore their antibacterial potential. We isolated 145 bacterial isolates from various soil, salt and water samples and found 23 actinomycete isolates effective against Mycobacterium smegmatis through cross-streak screening. Molecular identification confirmed that these isolates belonged to 14 genera of actinomycetes. Out of 23 extracts from these isolates, 15 ethyl acetate organic extracts exhibited strong antimycobacterial activities against M. smegmatis, M. tb H37Ra, and M. tb H37Rv, with MIC values between 125 and 31.25 µg/mL. Importantly, all 15 extracts demonstrated bactericidal activities at their respective MICs against M. tb H37Rv. The other 8 extracts displayed comparatively weaker MIC and MBC ranging 500-250 µg/mL and 1000-500 µg/mL respectively. These extracts were equally effective against drug-resistant and drug-susceptible M. tb clinical isolates. Furthermore, they showed broad antibacterial activity against both gram-positive and gram-negative bacteria, with MICs ranging from 500 to 31.25 µg/mL. The GC-MS analysis of the potent extracts revealed that a wide range of compounds including Phenolics, Peptides, Ergot alkaloids and their derivates may have contributed to anti-mycobacterial activity. The genetic diversity and significant antimicrobial properties of these actinomycetes from extreme environments highlight their potential for developing new antituberculosis and general antibiotic agents, particularly against MDR infections.