In the present study Streptomyces longisporoflavus was screened for antimicrobial activity against fourteen MDR pathogenic bacteria ( Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella typhimurium, Klebsiella pneumonia Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes), and fungi (Tricosporon mucoides, Candida albicans, Candida glabrata, Candida krusie, Candida dublinesis and Candida tropicalis) by using well- agar diffusion method. S.longisporoflavus showed high antimicrobial activity only against seven of the fourteen tested MDR bacteria and fungi (Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes and Candida tropicalis).Cultural conditions of S.longisporoflavus were optimized for maximizing growth and antimicrobial activity. The results under the optimized conditions recorded the maximum mycelial dry weight and significant antimicrobial activity against all the seven MDR pathogenic bacteria, with incubation period 8 days, at pH 7, temperature 55°C, media supplemented with potassium nitrate as nitrogen and starch as carbon sources. The highest diameters of inhibition zones by the antimicrobial materials were recorded with MDR Staph aureus followed by E.coli and proteus mirabilis (37, 35, and 34mm respectively) , at all optimal cultural conditions of S.longisporoflavus.
Key words: Streptomyces longisporoflavus, optimization, antimicrobial activity, MDR pathogenic bacteria and fungi.