Potential of Essential Oils from Different Mint Species Against Multidrug-Resistant Escherichia coli Strains Isolated from Clinical Cases in Poultry

The study presents the potential application of three essential oils (EOs) obtained from various mint species: peppermint (<i>Mentha piperita</i> L.), spearmint (<i>Mentha spicata</i> L.), and pennyroyal (<i>Mentha pulegium</i> L.), as alternative agents against multidrug-resistant <i>Escherichia coli</i> strains isolated from poultry. The aim of research was to determine the effectiveness of EOs from these mint species and their main chemical components (menthol, menthone, carvone, pulegone) against 19 clinical <i>E. coli</i> strains with varying drug susceptibility and the reference strain <i>E. coli</i> ATCC 25922. GC-MS analysis revealed a unique chemical profile for each mint species. In <i>M. piperita</i>, menthol (35.14%), trans-menthone (23.11%), and menthyl acetate (6.96%) were the dominant compounds. In <i>M. spicata</i>, the main components were carvone (58.61%) and 1,8-cineole (18.74%), while in <i>M. pulegium</i>, pulegone was the dominant ingredient (76.54%). Antibacterial activity tests showed that all tested <i>E. coli</i> strains, both susceptible and multidrug-resistant, were sensitive to the EOs. The strongest antibacterial activity was observed for peppermint oil (Minimal Inhibitory Concentration-MIC 0.5-2.0% <i>v</i>/<i>v</i>), which was attributed to its high menthol content. Menthol was also the most effective single component (MIC 0.125-0.5% <i>v</i>/<i>v</i>). The essential oils containing carvone and pulegone showed lower activity (MIC ≥ 2% <i>v</i>/<i>v</i>). Research indicates that mint EOs, particularly those rich in menthol, represent a promising alternative or complement in the treatment of infections caused by multidrug-resistant <i>E. coli</i> strains.