The Midgut Microbiota of Colombian Aedes aegypti Populations with Different Levels of Resistance to the Insecticide Lambda-cyhalothrin

SIMPLE SUMMARY: Aedes aegypti is a mosquito capable of transmitting many viral diseases such as dengue, Zika, and chikungunya. Since no effective treatments are available for these viruses, eliminating the mosquito with insecticides is vital to combat these diseases. However, the mosquito can generate resistance to the insecticide by changing its genes or its physiology. It has been recognized that the type of bacteria that live inside the mosquito’s gut can contribute to this resistance. In this study, we evaluated Ae. aegypti mosquitoes from six locations in Colombia to determine if they are resistant to lambda-cyhalothrin insecticide, and we analyze their gut microbiota. We observed resistance in five of the six areas. We compared the gut microbiota from susceptible and resistant mosquitoes and found specific bacteria in resistant mosquitoes that may play a role in insecticide resistance. Overall, our findings contribute to the understanding of insecticide resistance in Ae. aegypti that will generate alternatives for interventions to control this mosquito in Colombia. ABSTRACT: Insecticide resistance in Aedes aegypti populations is a problem that hinders vector control and dengue prevention programs. In this study, we determined the susceptibility of Ae. aegypti populations from six Colombian regions to the pyrethroid lambda-cyhalothrin and evaluated the presence of the V1016I mutation in the sodium channel gene, which has been broadly involved in the resistance to this insecticide. The diversity of the gut microbiota of these mosquito populations was also analyzed. Only mosquitoes from Bello were susceptible to lambda-cyhalothrin and presented a lower allelic frequency of the V1016I mutation. Remarkably, there was not an important change in allelic frequencies among populations with different resistance ratios, indicating that other factors or mechanisms contributed to the resistant phenotype. Treatment of mosquitoes with antibiotics led us to hypothesize that the intestinal microbiota could contribute to the resistance to lambda-cyhalothrin. Beta diversity analysis showed significant differences in the species of bacteria present between susceptible and resistant populations. We identified 14 OTUs of bacteria that were unique in resistant mosquitoes. We propose that kdr mutations are important in the development of resistance to lambda-cyhalothrin at low insecticide concentrations but insect symbionts could play an essential role in the metabolization of pyrethroid insecticides at higher concentrations, contributing to the resistant phenotype in Ae. aegypti.