Septic Infection Experiment
Given the impact of infection route on immune gene expression , we wanted to clarify whether the interaction between pesticides and infection outcomes might be infection route-dependent. We selected two populations, Coffee and Dorris, as representative populations that may demonstrate interactions between pesticide resistance and exposure on infection outcomes. Therefore, we exposed 14-day old larvae from control- and OP-regimes to control and OP oral diets (as described above) for three days, and then septically infected individuals withBtt and recorded their survival.
We produced a mixture of Btt cultures of vegetative cells from both the logistic growth and early stationary phase for septic infections as previously described , which caused around 50% mortality in preliminary experiments. We pricked larvae laterally between the head and second segment with an ultra-fine borosilicate needle dipped in the bacterial suspension and recorded survival after 24 hours. We repeated the experiment three times with 20 individuals per population (Coffee or Dorris), selection regime (OP selected and control) and pesticide treatment (OP exposure and control) each (n = 480).
Differences in survival between the control group (control selection regime, no pesticide) and the other groups were analyzed in a GLMM with experiment (block) and population as random factors and a binomial error distribution .