Benita Mercy R, Kannabiran K
Drug resistance by bacterial pathogens becomes a major health problem worldwide. Hence, it is important to search for broad spectrum of antibiotic from natural sources. Marine actinomycetes isolated from marine sediments collected at different sampling sites along the southeast coast of Bay of Bengal, India were investigated for antagonistic activity against selected drug resistant Gram positive bacterial pathogens. All actinomycetes isolates were screened for antibacterial activity against standard drug resistant ATCC strains. The potential isolate which showed higher inhibitory activity against drug resistant pathogens was mass cultured and the ethyl acetate (EA) extract of the cell free culture broth was tested for antibacterial activity. The biochemical, morphological and physiological characterisation of the isolate revealed that it was Gram-positive rod, sporulating and produced grey aerial mycelium. The spore chain morphology, and smooth surface morphology showed that it belongs to the genus Streptomyces. Based on Nonomura’s key for classification of Streptomyces and Bergey’s Manual of Determinative Bacteriology, the isolate was identified as Streptomyces species and designated as Streptomyces sp. VITBRK4. Purification and characterization of EA extract of the isolate by thin layer chromatography (TLC) and HPLC-DAD analysis showed the presence of indolo compound along with few other unidentified metabolites. The result of this study showed that the antibacterial activity of the EA extract against drug resistant strains may be due to indolo compound present in the extract.
