Antimicrobial activity of essential oils against foodborne multidrug-resistant enterococci and aeromonads in planktonic and biofilm state.

The selection and use of natural compounds with antimicrobial activity against foodborne pathogens is of major importance. The present study evaluated the antimicrobial activity of commercial essential oils against multidrug-resistant Enterococcus spp. and Aeromonas spp. Cymbopogon flexuosus and Thymus vulgaris essential oils presented the highest inhibitory zones against both bacterial groups ( p < 0.05). Subsequent determination of the minimum inhibitory concentrations showed values between 0.47 and 1.9 mg/ml for Aeromonas spp. and from 1.9 to 15 mg/ml for Enterococcus spp. The antimicrobial effect of C. flexuosus and T. vulgaris essential oils was also assessed against biofilms. Bacteria in biofilm state were subjected to 30 min or 1 h of exposure to each essential oil and eradication ability estimated by colony counting. Both essential oils exhibited antimicrobial activity against preformed Aeromonas biofilms, but were unable to successfully eradicate biofilms produced by enterococci, in the conditions under investigation. Nonetheless, the presumptive use of essential oils in the food industry should be considered in further investigations.