Effect of Lebanese Plant Extracts on Stress-Resistant Escherichia Coli and Application of the Hurdle Technologies

Abstract

The abundance of stress-resistant bacterial pathogens has been burdening food industries. In addition, customers’ demand for clean-label products has directed research toward finding suitable natural preservatives. Thus, this study investigated the antimicrobial activity of four Lebanese wild plant extracts (Lavandula angustifolia, Origanum marjoram, Ocimum basilicum, and Salvia fruticose) against eight Escherichia coli isolates of different resistant profiles (non-resistant (NR), heat-resistant (HR), antimicrobial-resistant (AMR), and isolates resistant to both heat and antimicrobial drugs). This activity was evaluated using the broth dilution method to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Moreover, the effect of the plant extracts was evaluated against HR isolates in combination with mild heat treatment at 65oC for 30 minutes and against AMR isolates to assess the hindrance of antimicrobial resistance. The results showed that the essential oils worked at an average concentration of 0.5% despite the resistance profile of the isolates. However, the water extracts were ineffective against any of the isolates. Also, the combination of 0.2% lavender EO and mild pasteurization significantly decreased the bacterial counts of the HR isolates. Lastly, the resistance to antibiotics was not affected by the EO treatment of E. coli.