Gut Microbiota Restructuring and Elizabethkingia Enrichment in Aedes albopictus Larvae Under Pyriproxyfen Exposure

Aedes albopictus transmits dengue, chikungunya, and Zika viruses, and its expanding range, together with widespread insecticide resistance, threatens the sustainability of chemical vector control. Pyriproxyfen (PPF) is an insect growth regulator used in mosquito control, but the relationship between gut bacteria and larval responses to PPF remains poorly characterized. We combined 16S rRNA gene amplicon sequencing with culture-dependent isolation to characterize gut bacterial communities in Ae. albopictus following acute PPF exposure and identify candidates for functional investigation. The 24 h median lethal concentration (LC50) for the Fuzhou population was 10.27 mg/L. Community profiles were compared among Fuzhou larvae dying at 2× LC50, surviving at 5× LC50, and receiving solvent alone; solvent-treated Foshan laboratory larvae served as an external population reference. Bacterial richness and Shannon diversity were lower in both exposed Fuzhou groups than in the Fuzhou solvent-treated control, and community structure differed among the four groups (PERMANOVA, R2 = 0.797, p = 0.001). Elizabethkingia accounted for 35.0% of bacterial reads in survivors, compared with 22.8% in non-survivors and 7.6% in Fuzhou solvent-treated controls, with significantly higher relative abundance in survivors than in either comparison group. Culture-dependent isolation from survivors yielded 29 isolates representing nine genera, including three isolates assigned to Elizabethkingia anophelis by 16S rRNA gene sequencing. Concordant sequencing and culture-based evidence, together with the recovery of viable isolates, positions Elizabethkingia as a tractable entry point into this question, opening a route to ask whether the larval microbiota can be managed to preserve the efficacy of pyriproxyfen-based control as resistance to other insecticide classes spreads.