(A) Survival of mutants for groups of AMPs reveals that loss of Imd-responsive Group B peptides (Drosocin, Attacins, and Diptericins) results in a strong susceptibility to infection (p<0.001), while loss of Group A or C peptides alone resists as wild-type (p>0.1 each). Group AB flies were as susceptible as ΔAMPs flies, and we observed a synergistic interaction between Group A and B mutations (A*B: HR =+2.55, p=0.003). (B) Further dissection of the mutations in Group B revealed that loss of Drosocin alone (DroSK4), or a deficiency lacking both Drosocin and Attacins AttA and AttB (Dro-AttABSK2) recapitulates the susceptibility of Group B flies. (C) By 18hpi, bacterial loads in individual Drosocin mutants or RelE20 flies are significantly higher than wild-type. (D) Heterozygote flies for DroSK4 and Df(2R)BSC858 (a deficiency removing Drosocin, Attacins AttA and AttB, and other genes) are strongly susceptible to E. cloacae infection. (E) Drosocin mutants in an alternate genetic background (yw) are susceptible to E. cloacae. One-way ANOVA: not significant = ns, and p<0.001 = *** relative to iso w1118.