Effect of metabolite extract of Streptomyces hygroscopicus subsp. hygroscopicus on Plasmodium falciparum 3D7 in vitro

Background: Malaria eradication has been complicated by the repeated emer-gence of antimalarial drug resistances. We aimed to determine whether a metabo-lite extract of Streptomyces hygrocopicus subsp. hygroscopicus could decrease the viability of Plasmodium falciparum 3D7 in vitro. Methods: S. hygroscopicus subsp. hygroscopicus isolates were inoculated and ferment-ed on the ISP4 medium. The fermented S. hygroscopicus was mixed with ethylacetate 1:5 (v/v), and the solvent phase was evaporated. Several concentra-tions of isolated extract was added to the P. falciparum 3D7 culture containing trophozoite and schizont stages in 24 wells plates when the degree of parasite-infected erythrocytes reached 5%, then incubated for 8 hours. DNA parasite den-sity was measured using flow cytometry, parasite degree and morphology were observed under microscopic by Giemsa-stained smears. Results: The metabolite extract affected the morphology of almost all of parasite asexual stages. Schizonts and trophozoites failed to grow and appeared damaged with pycnotic cores and loss of cytoplasmic content. At 8 hours there was a sig-nificant decrease in DNA parasite density in culture exposed to 2.6 mg/ml and 13 mg/ml (P = 0.002; P = 0.024) of the extract. The degree of parasite-infected erythrocytes was decreased from the beginning of exposure (0.02 mg/ml of the extract). There was a significant inverse correlation between the concentration of extract and the degree of parasite-infected erythrocytes as well as the density of DNA parasite (r = -0.772, P = 0.000; r =-0.753; P =0.000). Conclusion: Metabolite extract of S. hygroscopicus subsp. hygroscopicus causes mor-phological damage, decreases the degree of parasite-infected erythrocytes and the DNA density of P. falciparum 3D7 in vitro.