FIGURE 1.

Summary of the screening procedure. (A) Principles of the pathway-specific screen. The screen is predicted to identify inhibitors of specific steps in cell wall synthesis because such compounds inhibit the growth of the wild type strain (primary screen) while improving growth of the clpX strain (counter screen)–see text for details. (B) Screening workflow. A collection of 50,000 synthetic small molecules from the Maybridge screening collection was first screened for growth inhibition against the S. aureus wild type resulting in 828 active compounds. Next, a S. aureus clpX mutant was used in a growth-based counter-screen to identify 58 compounds capable of increasing the growth yield of the clpX mutant at 30°C (cut-off 1.5 fold increase in final yield as measured by optical density). Ten compounds were purchased for follow-up studies, and of these ten compounds, seven hit-compounds retained the ability to increase the final yield of S. aureus clpX cultures grown at 30°C in a microtiter plate growth assay and sensitized the highly resistant COL MRSA to at least one β-lactam antibiotic in a disc diffusion assay (summarized in Table 1).