Evaluation of Larvicidal Potential of Streptomyces extracts against Aedes Aegypti (Diptera: Culicidae)

Chemical pesticides are the main way to control mosquito population, but they are toxic to non-target organisms and have limited effectiveness against resistant mosquitoes. Actinobacterial metabolites are highly toxic, and their potential can be explored for alternative environment friendly insecticides. The current study evaluated methanolic crude extracts of 49 actinobacteria strains isolated from the Cholistan desert, Pakistan, for their larvicidal potential against fourth instar Aedes aegypti larvae. The extracts of five Streptomyces strains, including CD4-2, CD13-1, CD-1-1, CD13-6, and CD13-22, exhibited prominent larvicidal activity with LC50 values of 187.4, 188.8, 190.2, 190.4, and 282.8ppm, respectively, after 24 hours of exposure. This larvicidal potency was further increased to 97.8, 104.5, 113.5, 107.4, and 108.1ppm, respectively, after 48 hours of exposure.Additionally, 25 isolates exhibited antibacterial activity against drug resistance bacterial pathogens including Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Enterobacter species. The thin-layer chromatography analysis indicated the presence of compounds from different structural classes such as quinones, indole, flavonoids, terpenes, N-hetrocycles and actinomycins etc in the extracts. The findings in this study indicate that Streptomyces isolated from extreme environments such as deserts harbor significant larvicidal potential against dengue vectors. Additionally, these strains exhibit antibacterial activity against common human pathogens.The large-scale cultivation, solvent extraction and purification of the compounds from these Streptomyces strains may help to develop eco-friendly larvicidal compounds for controlling dengue vector.