High-throughput screening for small-molecule inhibitors of Staphylococcus epidermidis RP62a biofilms

Abstract

High-throughput screening (HTS) of 42 865 compounds was performed to identify compounds that inhibit formation of or kill Staphylococcus epidermidis RP62a biofilms. Three biological processes were assayed, including (1) growth of planktonic/biofilm bacteria, (2) assessment of metabolically active biofilm bacteria using a resazurin assay, and (3) assessment of biofilm biomass by crystal violet staining. After completing the three tiers (primary screening, hit confirmation, and dose-response curves), 352 compounds (representing ~0.8%) were selected as confirmed hit compounds from the HTS assay. The compounds were divided into groups based on their effectiveness on S. epidermidis biofilm properties. The majority of these affected both inhibition and killing of bacterial biofilm cultures. Only 16 of the confirmed hit compounds that have either an AC50 lower than 10 µM and/or Sconst ≥70 from those processed were selected for further study by confocal laser scanning microscopy (CLSM). The CLSM was used to evaluate the confirmed hit compounds on (1) inhibition of biofilm formation and (2) killing of preexisting S. epidermidis biofilms. Taken together, with further testing (e.g., disease-related conditions), such compounds may have applications as broad antimicrobial/antibiofilm use for prophylactic or therapeutic intervention to combat infections in surgical and intensive care clinics and battlefield settings.

Keywords: S. epidermidis RP62a; biofilms; high-throughput screening; inhibition; killing.