Antibacterial Activity of Clove, Oregano, Thyme, Eucalyptus, and Tea Tree Essential Oils against Escherichia coli and Klebsiella pneumoniae strains

Abstract Background: In view of the high recurrence rate of urinary tract infections and the increasing number of germs resistant to multiple antibiotics, the aim of the present study was to evaluate the antibacterial properties of clove, oregano, thyme, eucalyptus, tea tree essential oils (EOs) against 32 isolates of Escherichia coli and 28 isolates of Klebsiella pneumoniae from patients with urinary tract infections (UTI). Methods: The agar disk diffusion method was used to assess the susceptibility of these isolates to essential oils and the minimal inhibitory concentration (MIC), and the minimal bactericidal concentration (MBC) were determined. Results: Our results suggest that volatile phenols (such as carvacrol in oregano EO, thymol in thyme EO, and eugenol in clove EO) are more efficacious as antibacterial than non-aromatic compounds (such as eucalyptol in eucalyptus EO and terpinene derivatives in tea tree EO). Conclusion : The oregano EO, followed by thyme appear to have the highest efficacy against Escherichia coli and Klebsiella pneumoniae isolates investigated.