Contrasting Patterns of Asaia Association with Pyrethroid Resistance Escalation between the Malaria Vectors Anopheles funestus and Anopheles gambiae .

Microbiome composition has been associated with insecticide resistance in malaria vectors. However, the contribution of major symbionts to the increasingly reported resistance escalation remains unclear. This study explores the possible association of a specific endosymbiont, spp., with elevated levels of pyrethroid resistance driven by cytochrome P450s enzymes and voltage-gated sodium channel mutations in and Molecular assays were used to detect the symbiont and resistance markers (, , , and ). Overall, genotyping of key mutations revealed an association with the resistance phenotype. The prevalence of spp. in the FUMOZ_X_FANG strain was associated with the resistance phenotype at a 5X dose of deltamethrin (OR = 25.7; = 0.002). Mosquitoes with the resistant allele for the markers tested were significantly more infected with compared to those possessing the susceptible allele. Furthermore, the abundance correlated with the resistance phenotype at 1X concentration of deltamethrin ( = 0.02, Mann-Whitney test). However, for the MANGOUM_X_KISUMU strain, findings rather revealed an association between load and the susceptible phenotype ( = 0.04, Mann-Whitney test), demonstrating a negative link between the symbiont and permethrin resistance. These bacteria should be further investigated to establish its interactions with other resistance mechanisms and cross-resistance with other insecticide classes.