Microbicide Action of IAA and IAA/HRP on Staphylococcus Aureus

Abstract

Action of indole-3-acetic acid (IAA) in absence and presence of horseradish peroxidase (HRP) was evaluated on the virulence factors produced by Staphylococcus aureus: biofilm producer; enterotoxins producer (seb-gene, SEB); methicillin resistance (mecA) and control-stain by: i) dose-response on microorganism growth and minimum inhibitory concentration (MIC) by spectrophotometry at 625nm; ii) membrane damage by flow cytometry using fluorescence detector at 610nm and 530nm; iii) biofilm production by spectrophotometry at 570 nm; iii) antioxidant enzyme activity as catalase and superoxide dismutase by spectrophotometry at respective 240nm and 550nm. Dose-response on microorganism growth was seen and MIC by IAA alone was 40mM for biofilm, 50mM for SEB and control-stain, and 60mM for mecA; HRP potentiated the IAA action on biofilm, SEB and mecA. Subinhibitory IAA concentration increased membrane damage for only biofilm and control-strain; however in presence of HRP the injury was potentiate in all stains. Except for biofilm, all strains showed similar increase in catalase activity by IAA and IAA/HRP. Superoxide dismutase activity was similarly increased in presence of IAA and IAA/HRP for all stains. IAA alone or combined with HRP presents microbicide action on S. aureus with different pathological characteristics; probably involving reactive oxygen species since increased activity of antioxidant enzymes.