Selective Chemical Inhibition of agr Quorum Sensing in Staphylococcus aureus Promotes Host Defense with Minimal Impact on Resistance
Figure 2
Savirin inhibits AgrA function in S. aureus both in vitro and within the organism.
(A) In silico docking of savirin to AgrAC from S. aureus. Space-filled representation of the C-terminal agrA DNA binding domain (gray) bound to target DNA. Surface residues that differ in S. epidermidis are blue, a naturally occurring dysfunctional mutation is shown in orange, and an essential Cys is shown in yellow. Savirin is shown in stick representation. An enlarged view of the boxed area shows the savirin docking site and surrounding residues. (B) Effect of increasing concentrations of savirin (5–160 µg ml−1 or 13.5–432 µM) vs vehicle on AgrAC-FAM labeled oligonucleotide complex formation by EMSA. The IC50 for savirin inhibition was quantified by densitometry of the bands. Data are representative of 3 independent experiments. (C) Effect of increasing concentrations of savirin (0.4–6.3 µM or 0.29–2.33 µg ml−1) vs vehicle on agrA reporter activation in an agr null strain expressing a plasmid for agrA where agr::P3 drives luminescence, AH3048, after 6 hr of growth. AIP2 as an inhibitor of non-agrII AgrC signaling was used as a specificity control. Viability is represented as OD600. Data are represented as the mean ± SEM of quadruplicates of a representative experiment of 3 independent experiments. ***p<0.001 **p<0.01, *p<0.05 by two-tailed Student's t-test.