Purpose: The purpose of this research is to determine the synergistic antimicrobial effect of carvacrol and zinc oxide nanoparticles (ZnO NPs) against C. jejuni as an alternative of antibiotic treatments.
Methods: Antimicrobial susceptibility of carvacrol, ZnO NPs, and a combination of both agents were tested against C. jejuni cocktail (a mixture of three strains). Macrobroth dilution broth adopted from Clinical and Laboratory Standard Institute guideline was conducted as a method to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of each antimicrobial treatment.
Results: MIC range of carvacrol was 13.5 µg/ml to 27 µg/ml. MBC of carvacrol (27 µg/ml) was effective to achieve 4.83 ± 0.11 log reduction (P<0.05) after 4 hours of treatment at 37°C. MIC range of ZnO NPs was 12.5 µg/ml to 25 µg/ml. MBC of ZnO NPs (25 µg/ml) was effective to achieve 4.81 ± 0.71 log reduction (P<0.05) after 4 hours of treatment at 37°C. Individual treatment of carvacrol (13.5 µg/ml) or ZnO NPs (12.5 µg/ml) did not show a bactericidal effect. However, a combination of 13.5 µg/ml of carvacrol and 12.5 µg/ml of ZnO NPs was effective to show a synergistic antimicrobial effect with 4.88 ± 0.08 log CFU/ml reduction (P<0.05) after 8 hours of treatment at 37°C.
Significance: These results suggest that carvacrol and ZnO NPs may potentially work synergistically to inactivate C. jejuni. Further research should be conducted to study the antimicrobial mechanism of this treatment.