FIG 3.

Efflux pump gene expression before or after antiseptic exposure. (A and B) The expression of norA, qacA, and the two qacC variants after exposure to 1 μg/ml of CHX or subinhibitory concentrations of BKC {2.5 μg/ml for RN4220 and RN4220 (pCN38-qacC [pSK89]) or 5 μg/ml for RN4220 (pCN38-qacA qacR) and RN4220 (pCN38-qacC [pSK41])} was examined. Fold differences in gene expression compared to expression prior to the addition of antiseptic were calculated at 15, 30, and 60 min. The geometric means from ≥3 biologically independent replicates are plotted (except for panel B; two replicates were completed for RN4220 (pCN38-qacC [pSK89]), as no change was observed). The dotted lines indicate a 2-fold increase or decrease in expression. (C and D) The expression of qacA in S. aureus USA300 strains was examined after exposure to 1 μg/ml of CHX or 5 μg/ml of BKC. For comparison, expression results from RN4220 (pCN38-qacA qacR) were included. Fold differences in gene expression compared to expression prior to the addition of antiseptic were calculated at 15, 30, and 60 min. The geometric means from ≥3 biologically independent replicates are plotted. (E) The basal level relative expression of qacA compared to the 16S gene was examined in the indicated strains. The geometric mean is plotted, and the error bars indicate the geometric SD. ****, P < 0.0001 compared to the values for all other strains. Significant differences were determined by one-way ANOVA with Tukey’s correction for multiple comparisons.