IMI-exposed D. melanogaster are more susceptible to septic infection with Serratia marcescens. (A) Survival curves for newly eclosed Imd pathway mutant (Rel
−/−) and WT Canton-S flies subjected to septic infection (S. marcescens NCIMB 11782) with or without concurrent exposure to IMI. All statistical symbols are representative of comparison made to infected WT Canton-S controls using the log-rank (Mantel-Cox) test. (B) Pathogen load of S. marcescens NCIMB 11782 during septic infection of WT flies was determined by plating surface-sterilized whole fly homogenates on LB agar medium. Colony forming units (CFU) per fly obtained at each time point represents the mean ± standard deviation (unpaired, two-tailed t-tests) of 9 biological replicates (n = 36 for each group). (C) Pathogen load of S. marcescens Db11 during oral infection of WT larvae was determined by plating surface-sterilized whole larvae homogenates on LB with 100 μg/ml streptomycin medium. CFU per larvae obtained at each time point represents the mean ± standard deviation (unpaired, two-tailed t-tests) of 9 biological replicates for each time point (n = 36 total for each group). (D,E) TotA and Dpt gene expression of newly eclosed WT flies that were subjected to septic injury with or without S. marcescens NCIMB 11782 infection and with or without concurrent exposure to IMI. All samples were taken 6 h after experimental start time. Gene expression was quantified by RT-qPCR and is relative to vehicle flies that were subjected to septic injury with a sterile needle. Means ± standard deviations (two-way ANOVA) from 3 biological replicates (each consisting of 10 flies) with triplicate technical repeats are shown. *p < 0.05 **p < 0.01, ***p < 0.001, ****p < 0.0001.