Western Kenyan Anopheles gambiae showing intense permethrin resistance harbour distinct microbiota

Abstract

Background Insecticide resistance poses a growing challenge to malaria vector control in Kenya and around the world. Following evidence of associations between the mosquito microbiota and insecticide resistance, the microbiota of Anopheles gambiae sensu stricto (s.s.) from Tulukuyi village, Bungoma, Kenya, with differing permethrin resistance profiles were comparatively characterized. Methods Using the CDC bottle bioassay, 133 2–3 day-old, virgin, non-blood fed female F1 progeny of field-caught An. gambiae s.s. were exposed to five times (107.5 µg/ml) the discriminating dose of permethrin. Post bioassay, 50 resistant and 50 susceptible mosquitoes were subsequently screened for kdr East and West mutations, and individually processed for microbial analysis using high throughput sequencing targeting the universal bacterial and archaeal 16S rRNA gene. Results 47 % of the samples tested (n = 133) were resistant, and of the 100 selected for further processing, 99 % were positive for kdr East and 1 % for kdr West. Overall, 84 bacterial taxa were detected across all mosquito samples, with 36 of these shared between resistant and susceptible mosquitoes. A total of 20 bacterial taxa were unique to the resistant mosquitoes and 28 were unique to the susceptible mosquitoes. There were significant differences in bacterial composition between resistant and susceptible individuals (PERMANOVA, pseudo-F = 2.33, P = 0.001), with presence of Sphingobacterium, Lysinibacillus and Streptococcus (all known pyrethroid-degrading taxa), and the radiotolerant Rubrobacter, being significantly associated with resistant mosquitoes. On the other hand, the presence of Myxococcus, was significantly associated with susceptible mosquitoes. Conclusions This is the first report of distinct microbiota in An. gambiae s.s. associated with intense pyrethroid resistance. The findings highlight differentially abundant bacterial taxa between resistant and susceptible mosquitoes, and further suggest a microbe-mediated mechanism of insecticide resistance in mosquitoes. These results also indicate fixation of the kdr East mutation in this mosquito population, precluding further analysis of its associations with the mosquito microbiota, but presenting the hypothesis that any microbe-mediated mechanism of insecticide resistance would be likely of a metabolic nature. Overall, this study lays initial groundwork for understanding microbe-mediated mechanisms of insecticide resistance in African mosquito vectors of malaria, and potentially identifying novel microbial markers of insecticide resistance that could supplement existing vector surveillance tools.

Integration of whole genome sequencing and transcriptomics reveals a complex picture of insecticide resistance in the major malaria vector Anopheles coluzzii

“…An association between the microbial composition and resistance was seen in these samples, something previously noted in resistant populations 26,28,45 . However, even though the colonies were maintained in the same insectary by the same technician, we cannot rule out stochastic changes due to bottlenecking of the colony, which requires further exploration.…”

Overabundance of Asaia and Serratia Bacteria Is Associated with Deltamethrin Insecticide Susceptibility in Anopheles coluzzii from Agboville, Côte d’Ivoire

“…There is increasing evidence for an association between insecticide resistance phenotype ( 38 , 41 , 43 ) and Anopheles spp. microbiota.…”

“…gambiae complex, the main malaria vectors in sub-Saharan Africa, is limited to recent reports of significant enrichment of known pyrethroid degrading taxa ( Sphingobacterium , Lysinibacillus , and Streptococcus ) in permethrin-resistant An. gambiae sensu stricto (s.s.) from Kenya ( 43 ). To address this deficit, we comparatively characterized the bacterial microbiota of An.…”

The microbiome and mosquito vectorial capacity: rich potential for discovery and translation

“…Gut-associated microbiota may also indirectly affect mosquito lifespan by mediating resistance to insecticides. Evidence is emerging that mosquitoes with differing resistance status have distinct microbiomes [ 143 , 144 ], but further work is required to investigate the causality and the mechanisms underpinning these associations. Streptococcus , Pseudomonas , Klebsiella, and Pantoea correlated with insecticide resistance in An.…”