Pyrogallol impairs staphylococcal biofilm formation via induction of bacterial oxidative stress

Aims: To examine the effect of the phenolic compound pyrogallol on staphylococcal biofilm formation. Methods and results: In crystal violet biofilm assays, pyrogallol-reduced biofilm formation in Staphylococcus epidermidis ATCC 35984, Staph. epidermidis NRRL-B41021, Staphylococcus aureus USA300, and Staph. aureus Newman, without significantly impairing bacterial viability. Pyrogallol-mediated impairment of biofilm formation was likely due to induction of bacterial oxidative stress, as its effect was greater in catalase-deficient versus WT Staph. aureus, and biofilm production was rescued by exogenous catalase. The effect of pyrogallol on staphylococcal biofilm formation mirrored that of the known oxidant hydrogen peroxide, which also reduced biofilm formation in a dose-dependent manner. Conclusions: Pyrogallol reduces biofilm formation in S. aureus and Staph. epidermidis in a mechanism involving induction of bacterial oxidative stress. Impact Statement Staphylococcus aureus and Staph. epidermidis are hospital- and community-acquired pathogens that exhibit increasing levels of antibiotic resistance. New strategies for treating bacterial infections include antivirulence compounds that target pathogenic traits such as biofilm formation. We demonstrate that pyrogallol impairs staphylococcal biofilm production, potentially via induction of bacterial oxidative stress. These findings demonstrate antibiofilm properties of pyrogallol and highlight a role for oxidative stress in modulating Staphylococcus biofilm formation.