A Novel Bacterial-Mediated Method for the Differentiation of Aedes spp. Larvae in Mixed-Nursery Assays and Its Application in the Determination of Vegetative Lysinibacillus sphaericus Biocontrol Efficiency in Invasive Vector Eradication

The establishment of Aedes aegypti and the recent invasion of Aedes albopictus has put Colombia at risk, as it now harbours two arboviral vector species. Studies have shown the susceptibility of Aedes aegypti to the vegetative toxins produced by Lysinibacillus sphaericus. This study aims to determine the potential of two L. sphaericus strains in the control of both Aedes species present in Colombia, in both single and mixed species nurseries. Given the similarities between both species, there exists a need to differentiate them for the development of precise control strategies. Accordingly, mixed nurseries employed a red fluorescent protein (mRFP)-expressing Escherichia coli strain as a differentiator. Coloration-aided differentiation facilitated the analysis of mixed nursery treatments and provided deeper scrutiny into the variables at play. This showed an increase in the biocontrol efficiency, pointing to probable ecological variables. Bioassays involving Ae. albopictus showed a lower resistance to the one reported for Ae. aegypti in single-species nurseries. The study concludes that the use of E. coli strains expressing fluorescent proteins are useful tools to be employed in areas like public health entomology. Moreover, it was found that the use of L. sphaericus strains for biocontrol of vector mosquitoes is a viable alternative to chemical insecticides.