LAUSR

Abstract Spread of Multi-Drug Resistant (MDR) bacteria prompted the surge in need for new antimicrobial agents, especially those found in nature. Ilex paraguariensis commonly known as Yerba Mate, a plant native to South America, is known for its many pharmacological properties. In this study, the aqueous extracts of Yerba Mate were tested for antibacterial activity against different bacterial species. A promising activity was shown against Staphylococcus aureus (standard and clinical strains), Klebsiella pneumoniae (standard strains) and Acinetobacter baumanii (standard and clinical strains) with Minimum Inhibitory Concentrations (MICs) of 1.88–3.75 mg/mL, 1.88 mg/mL and 2.5–10 mg/mL respectively. Metabolites produced after in-vitro digestion of Yerba Mate extracts gave similar antibacterial activity against S. aureus. Combination assays between Yerba Mate extracts and different classes of antibiotics suggest an additive effect with the antibiotic Clarithromycin and an antagonistic effect with Gentamicin when tested on S. aureus strains of different profiles of resistance. Furthermore, Yerba Mate was able to delay coagulase activity of S. aureus strains when incubated with the extract at ½ MIC concentration. Further work should be done in order to isolate the compound(s) responsible for Yerba Mate's antibacterial activity and to understand its mechanism of action.