Atomic force microscopy evidences of bacterial cell damage caused by propolis extracts on E. coli and S. aureus

Abstract The interaction of the aqueous extract of green propolis with the bacterial envelope was investigated using atomic force microscopy on E. coli and S. aureus, as Gram-negative and Gram-positive model microorganisms. The bacteria were incubated in the extracts with variable proportions of water/ethanol, i.e., in different concentrations of total phenolic and flavonoids, for 4 and 12 hours. All extracts exhibited antibacterial action with higher activity (lower MIC) for full ethanolic extract (100% alcohol) against both strains, what was attributed to a synergistic interaction of ethanol...