New strains of <I>Bacillus thuringiensis subsp. israelensis</I> highly toxic for <I>Aedes aegypti</I> and <I>Culex pipiens pipiens</I>

Bacillus thuringiensis subsp. israelensis (Bti) is a known subspicies of crystal-forming entomopathogenic bacteria used to control blood-sucking mosquitoes. In this work, we isolated three different strains of Bti 4369, 4929 and 4999 from the wild larvae midgut of blood-sucking mosquitoes Aedes flavescens . The bacterial isolates were identified by the 16S rRNA gene and serotype determination revealed that the strains belonged to Bt subsp. israelensis H14. The strains had differences in bacterial colony morphology, a number of biochemical characteristics and protein endotoxin profiles. The isolated strains Bti 4369 and 4999 showed high insecticidal activity against Culex pipiens pipiens and Aedes aegypti larvae, with LC50 values of 1.47 ×108 ‒2.26 × 108 spores/ml 24 hours after treatment. The value for strain Bti 4929 LC50 was 32.7‒35.9 × 108 spores/ml. The new isolated strains of Bacillus thuringiensis subsp. israelensis have high potential for the development of ecological friendly bioinsecticides for the control of blood-sucking mosquitoes.