Evaluation of the Antibacterial, Antileishmanial, and Cytotoxic Potential of Secondary Metabolites of Streptomyces Kronopolitis

Abstract

This study aimed to evaluate the antibacterial, leishmanicidal, and cytotoxic potential of metabolites produced by bacteria isolated from rhizosphere soil samples. The bacterium was identified by molecular techniques as Streptomyces kronopolitis. A preliminary screening was carried for the antimicrobial activity of S. kronopolitis, demonstrating activity against Staphylococcus aureus ATCC 6538, Corynebacterium diphtheriae ATCC 27010, C. diphtheriae ATCC 27012, and Mycobacterium abscessus, with inhibition halos of sizes 25, 36, 29, and 33 mm, respectively. To obtain secondary metabolites, the bacteria was subjected to submerged fermentation, and the metabolites were extracted using the liquid-liquid method with ethyl acetate. There was a similar MIC for M. abscessus and the two strains of C. diphtherium, reaching a concentration of 0.125 mg/mL, while that of S. aureus was 0.048 mg/mL. Assays for leishmanicidal activity and cytotoxicity against HEp-2 cells and red blood cells were performed. The metabolite showed IC50 of 9.0 ± 0.9 µg/mL and CC50 of 226.2 µg/ ml. This metabolite does not have hemolytic activity and is more selective for parasites than for mammalian cells, with a selectivity index of 24.85. Thus, the studied metabolite may be a strong candidate for the development of less-toxic drugs to treat diseases caused by pathogens.