Isolation and characterization of an antibiotic adjuvant from Streptomyces thermoviolaceus SRC3 strain associated with fresh water sediment

The occurrence of extensive antibiotic sresistant bacteria increases the demands for finding new sources of antimicrobial agents. Microbial natural products, particularly those produced by actinobacteria, are the main source of novel bioactive metabolites In the present study,a total of 39 actinobacteria strainswereisolated from fresh water sediments and subjected to antogonistic activity test against human pathogenic germs. The most active antibiotic producer SRC3 (active against Salmonella Typhi ATCC14028, Vibrio choleraeATCC14035, MRSA ATCC 43300 and Candida albicans ATCC10231) was selected. The isolate was identified as Streptomycesthermoviolaceus SRC3 based on 16S rRNA sequencing, morphological and physiological analyses. Optimization of the culture medium for antibacterial compound production was performed using statistical methodology based on experimental designs. The metabolite responsible for the bioactivities was purified, structurally characterized (by NMR, MS, UV and IR analyses) and identified as streptazolin, recently reported as a promising antibiotic adjuvant.