Fold-change in fluorescence of H33342 at steady state levels of accumulation in efflux pump gene deletion mutants compared with the parental isolate. Three separate experiments showed consistent results and the average fold change is shown. The standard deviation represents variation between three replicates of the assay. Asterisks indicate significant differences (P ≤ 0.05) in accumulation compared with the parental strain. Panel A, R2 and mutants. Panel B, DB and mutants.