Western Kenyan Anopheles gambiae s.s. showing intense permethrin resistance harbor distinct microbiota

Abstract

BackgroundInsecticide 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, we comparatively characterized the microbiota of An. gambiae s.s. from Tulukuyi village, Bungoma, Kenya, with differing permethrin resistance profiles.MethodsUsing 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 (107.5μg/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.Results47% 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 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 (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.ConclusionThis 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. Our 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 malaria vectors, and potentially identifying novel microbial markers of insecticide resistance that could supplement existing vector surveillance tools.

Overabundance of Asaia and Serratia bacteria is associated with deltamethrin insecticide susceptibility in Anopheles coluzzii from Agboville, Côte d’Ivoire

“…arabiensis [42], and An. gambiae s.s [43]. This study is the rst to detect an increase in alpha diversity in resistant mosquitoes with other studies reporting no difference [39], [43] or a decrease [80].…”

“…gambiae s.s [43]. This study is the rst to detect an increase in alpha diversity in resistant mosquitoes with other studies reporting no difference [39], [43] or a decrease [80]. There are multiple potential reasons for the decreased microbial diversity previously identi ed, including processing of individuals rather than pooled mosquitoes, host species-speci c differences, and variability among geographical collection sites [80].…”

“…There is increasing evidence for an association between insecticide resistance phenotype [38], [43], [79] and Anopheles spp. microbiota.…”

“…gambiae complex, the main malaria vectors in sub-Saharan Africa, is limited to recent reports of signi cant 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 de cit, we comparatively characterised the bacterial microbiota of An.…”

Overabundance of Asaia and Serratia bacteria is associated with deltamethrin insecticide susceptibility in Anopheles coluzzii from Agboville, Côte d’Ivoire

“…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 characterised the bacterial microbiota of An.…”