Background: Antibiotic resistance transmission through the food chain is considered as a major health challenge. The combination of essential oils (EOs) with synergistic or additive effects regarding enhancing the antimicrobial activity is an applied approach for controlling foodborne pathogens and improving food safety. The aim of this study was to evaluate the combined effect of Cinnamomum camphora (cinnamon) and Syzygium aromaticum (clove) EOs against TEMbla produced by Escherichia coli isolated from poultry colibacillosis.
Methods: To this end, 100 E. coli isolated from the viscera of broilers suspected of colibacillosis, were examined to detect the ESBL produced by the combined disk method according to The Clinical and Laboratory Standards Institute (CLSI). In addition, TEMbla presence was detected by the polymerase chain reaction method. Finally, the antibacterial activity of cinnamon and clove EOs was studied against TEMbla harboring isolates alone and in combination with the broth microdilution method and fractional inhibitory concentration (FIC) index.
Results: Based on the results, 32/88 (36.3%) of the tested samples produced ESBL and 20/32 (62.5%) were found to harbor TEM. All the TEMbla produced by E. coli investigated by the broth microdilution assay were sensitive to cinnamon and clove EOs in the range of 400 to 1600 and 800 to 3200 ppm, respectively. FIC indices (ranging from 0.56 to 1) suggested their synergistic inhibitory effect on nine isolates and additive inhibitory effect against 11 isolates.
Conclusions: The results of this study indicated that the combination of cinnamon and clove can inhibit the growth of E. coli harboring the TEMbla gene and thus it can be suggested as a safe bio-preservative. However, further studies should be conducted to investigate the potential interaction between the EOs and food matrix components.