Evaluation of the Antibacterial Effect of Carvacrol Alone and in Combination with the Antibiotic Cefixime Against Escherichia coli O157:H7

The use of plant compounds and their derivatives, such as extracts and essential oils, for combating infectious agents has attracted a great deal of scientific attention. One of the active antimicrobial compounds with plant origin is carvacrol.

The present study aimed to evaluate the antibacterial activity of carvacrol alone and in combination with the antibiotic cefixime against Escherichia coli O157:H7.

The antibacterial properties of carvacrol and cefexime were evaluated by determining the Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), and disk diffusion method. The checkerboard assay was used to evaluate the interaction between the carvacrol and cefexime and to determine the fractional inhibitory concentration.

The results showed that the MIC and MBC of carvacrol and cefexime against E.coli O157:H7 were 250, 250 μg/ml (MIC, MBC) and 128, 128 μg/ml (MIC, MBC), respectively. In the checkerboard test, carvacrol was found to have a synergistic interaction with antibiotic cefixime against E. coli O157:H7 (FIC index=0.5).

Due to the significant antibacterial activity of carvacrol, the present study introduced this agent as a new antibacterial drug with a natural origin. In addition, since carvacrol significantly increased the antibacterial potential of cefixime (synergistic properties), it could be considered as an effective compound for increasing the antibacterial power of cefixime antibiotic.