Mitracarpus frigidus is active against Salmonella enterica species including the biofilm form

Abstract Salmonella spp. are a group of bacteria important to salmonellosis, a common infection frequently related to human contamination. In this context, new strategies to prevent or control these microorganisms are considered to be of global importance. The Mitracarpus frigidus aerial parts extracted by methanol (MFM) have several biological activities including an antimicrobial effect. Here, the MFM action against S. Typhimurium and S. Enteritidis planktonic cells and biofilms was investigated. The studies of planktonic bacteria [minimal inhibitory concentration, bacterial abundance, bacteria viability, nucleotide leakage, crystal violet permeability and Outer Membrane (OM) permeability] showed that MFM affects the bacterial wall by interfering with the OM permeability, which leads to growth inhibition. The biofilm studies (adhesion, effect on established biofilms, matrix composition, and structure) demonstrated that MFM reduces the biofilm adhesion prior to its formation, decreasing the total pre-formed biofilm and interfering with the matrix composition. Moreover, scanning electron microscopy analyses from both strains revealed clear ultrastructural changes on bacterial cell surface induced by MFM treatment. Altogether, our results demonstrated that MFM is active against the Salmonella strains evaluated, including the quinolone resistant one, being relevant in situations where this bacterium is involved, especially in salmonellosis conditions.