Mosquitoes of many species are key vectors in disease transmission, causing millions of fatalities worldwide each year. Insecticidal formulations based on Bacillus thuringiensis have been considered one of the most effective, ecologically safe, and long-lasting methods of managing insect pests. We established the isolation, identification, genetic characterization, and biological function of novel B. thuringiensis strains with strong control efficacy on mosquitoes. A collection of eight B. thuringiensis strains was isolated and identified as containing genes encoding typical endotoxins. Under light and scanning electron microscope, typical crystal forms of various shapes were observed in the B. thuringiensis strains. A total of fourteen cry and cyt genes were identified in the strains analyzed. While the B. thuringiensis A4 strain had twelve cry and cyt genes in the genome, not all the genes were expressed, and only a few protein profiles were detected. The eight B. thuringiensis strains showed larvicidal activity (LC50 range: 1.4–28.5 µg/ml and LC95 range: 15.3-130.3 µg/ml). Interestingly, the B. thuringiensis A4 strain showed a high level of toxicity to mosquito larvae and adults, as detected by bioassays under controlled conditions. These new findings show that the novel B. thuringiensis A4 strain could be used as a favorable candidate source to control larvae and adult mosquitoes in a sustainable manner that is friendly to the environment.

Mosquitoes of many species are key disease vectors, killing millions of people each year. Bacillus thuringiensis-based insecticide formulations are largely recognized as among the most effective, ecologically safe, and long-lasting methods of managing insect pests. New B. thuringiensis strains with high mosquito control effectiveness were isolated, identified, genetically defined, and physiologically characterized. Eight B. thuringiensis strains were identified and shown to carry endotoxin-producing genes. Using a scanning electron microscope, results revealed typical crystal forms of various shapes in B. thuringiensis strains. Fourteen cry and cyt genes were found in the strains examined. Although the genome of the B. thuringiensis A4 strain had twelve cry and cyt genes, not all of them were expressed, and only a few protein profiles were observed. The larvicidal activity of the eight B. thuringiensis strains was found to be positive (LC50: 1.4–28.5 g/ml and LC95: 15.3-130.3 g/ml). Bioassays in a laboratory environment demonstrated that preparations containing B. thuringiensis spores and crystals were particularly active to mosquito larvae and adults. These new findings show that the novel preparation containing B. thuringiensis A4 spores and crystals mixture might be used to control larval and adult mosquitoes in a sustainable and ecologically friendly manner.