<i>Streptomyces</i>-derived actinomycin D inhibits biofilm formation by <i>Staphylococcus aureus</i> and its hemolytic activity

<p><i>Staphylococcus aureus</i> is a versatile human pathogen that produces diverse virulence factors, and its biofilm cells are difficult to eradicate due to their inherent ability to tolerate antibiotics. The anti-biofilm activities of the spent media of 252 diverse endophytic microorganisms were investigated using three <i>S. aureus</i> strains. An attempt was made to identify anti-biofilm compounds in active spent media and to assess their anti-hemolytic activities and hydrophobicities in order to investigate action mechanisms. Unlike other antibiotics, actinomycin D (0.5 μg ml⁻¹) from <i>Streptomyces parvulus</i> significantly inhibited biofilm formation by all three <i>S. aureus</i> strains. Actinomycin D inhibited slime production in <i>S. aureus</i> and it inhibited hemolysis by <i>S. aureus</i> and caused <i>S. aureus</i> cells to become less hydrophobic, thus supporting its anti-biofilm effect. In addition, surface coatings containing actinomycin D prevented <i>S. aureus</i> biofilm formation on glass surfaces. Given these results, FDA-approved actinomycin D warrants further attention as a potential antivirulence agent against <i>S. aureus</i> infections.</p