Isolation and Characterization of Streptomyces platensis from Soil and Evaluation of its Activity against Human Pathogenic Microorganisms

The search for novel antibiotics has long been a primary focus of biomedical research, with actinobacteria recognized as one of the most prolific sources of bioactive secondary metabolites. The genus Streptomyces is particularly well known for producing antimicrobial compounds that can serve as alternatives to synthetic antibiotics. In the present study, Streptomyces strains were isolated from soil samples collected in the Wadi Qandil region, Latakia, using Starch Casein Agar, ISP2 medium, and Actinomyces Isolation Agar. The isolates exhibited gray aerial and substrate mycelia with spiral spore chains and no production of diffusible pigments. Antimicrobial activity of the isolated Streptomyces sp. was evaluated against clinically relevant human pathogens. The results revealed inhibitory effects against both Gram-negative bacteria (Escherichia coli, Enterococcus faecalis) and Gram-positive bacteria (Staphylococcus aureus), with larger inhibition zones observed against Gram-positive strains. Using the disk diffusion method, inhibition zones of the ethyl acetate extract ranged from 19.5 mm against E. coli to 25 mm against S. aureus. These findings highlight the potential of soil-derived Streptomyces as a promising source of natural antimicrobial agents against multidrug-resistant pathogens