• Enhanced Efficacy of Ceftazidime Against Escherichia coli Through Synergism with Thymol
  • Mehrsa Karim,1,* Mina Shirmohammadpour,2 Sajjad jafari,3 Bahman Mirzaei,4 Faeze Khanizade,5
    1. Department of Microbiology and Virology, Faculty of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran
    2. Department of Microbiology and Virology, Faculty of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran
    3. Department of Microbiology, Faculty of Medicine, Urmia University of Medical Sciences, Urmia, West Azerbaijan, Iran
    4. Department of Microbiology and Virology, Faculty of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran
    5. Department of Microbiology and Virology, Faculty of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran


  • Introduction: This study looked into the antibacterial synergism of thymol/ceftazidime on Escherichia coli (E. coli) bacteria.
  • Methods: The MIC-MBC method was used to assess the antimicrobial effect of thymol and ceftazidime, separately and in combination, at varying doses on E. coli ATCC25922. The MIC-MBC approach was used to assess the antimicrobial properties of a drug that showed synergistic effects on twenty clinical strains of E. coli bacteria. Using an FTIR device, the compound's molecular interactions, functional groups, and chemical bond identification were examined. In this study, the checkered method, time killing curve, biofilm inhibition on E. coli ATCC25922 bacteria, and hemolysis method and MTT method were used to investigate the cytotoxicity on human skin fibroblast cells (Ffk) and red blood cells (RBCs) in human subjects. The effects of the A1 compound were synergistic.
  • Results: The study's findings demonstrated that when applied to E. coli ATCC25922, the antimicrobial activities of thymol, ceftazidime, and thymol/ceftazidime (A1 compound) were, respectively, 256, 16, and 16/8µg/ml (FICI: 1). The A1 compound exhibited antibacterial properties on clinical strains of E. coli that were 8-1024/4-128 µg/ml, respectively. The combined mode demonstrated a longer time curve for killing the aforementioned bacteria than the individual modes. These compounds included OH bonds, proteins, polyphenols, C=O Amide I band, C-O-C polysaccharide, and C-Namide III band; however, one compound, C=C conjugated, C≡C, demonstrates the relationship between thymol/ceftazidime. Thymol, ceftazidime, and A1 compound all showed biofilm inhibition rates of 29.51%, 22.14%, and 75.51% against E. coli, respectively. The corresponding toxicity values for thymol, ceftazidime, and A1 compound were 36.12, 9.54, and 6.83 for human RBCs and 19.66, 8.36, and 6.68 for human Ffk cells.
  • Conclusion: The results of this study demonstrated that thymol with ceftazidime has strong antibacterial and antibiofilm effects, even in light of ceftazidime's resistance in treating E. coli-related disorders. This compound's toxicity on multiple cells was the same, and further testing can be done on it.
  • Keywords: Escherichia coli, Thymol, Ceftazidime, Synergistic