Antimycobacterial Properties and Metabolite Profiling of Fish Gut-Associated Streptomyces sp. MCA2

Background: Infectious diseases such as tuberculosis and other opportunistic diseases affecting the lungs are major threats concerning public health. These pathogens have gained resistance to the currently available drugs which has prompted the discovery of novel antibiotics to fight against such pathogenic organisms. With unique pharmaceutical and biotechnological applications, Actinobacteria are considered possessing rich source of natural products. Biodiscovery of actinobacterial metabolites depends on the identification and recovery from unexplored environments and effective assessment of their metabolites. Literature states that among various ecosystems, fish are promising yet understudied source. Methods: Potential strain was screened from 13 fish gut-associated actinobacterial strains for their antimycobacterial and antitubercular properties. Ideal fermentation methodology has opted for bioactive metabolite production. Optimization procedures, minimum inhibitory concentration determination, characterization studies, and metabolite profiling through gas chromatography mass spectrometry were performed. Results: Potential strain MCA2 was selected for their antagonistic activity against Mycobacterium smegmatis. Bioactive metabolite of potential strain was produced through agar surface fermentation and extracted using ethyl acetate. Antitubercular activity was confirmed by >50% reduction in relative light unit against Mycobacterium tuberculosis H37Rv. The potential strain MCA2 was identified as Streptomyces sp. based on its phenotypic characteristics. Conclusion: The outcome of this study outlined the antimycobacterial potential of isolated fish gut-associated Streptomyces sp. strain confirming that fish guts are promising sources for isolating metabolites active against tuberculosis and other nontuberculous mycobacterial diseases.