• In Vitro Synergy Between Thymol and Ampicillin Against Escherichia coli Clinical Strains
  • Tarannom Mohammadi,1 Mina Shirmohammadpour,2 Sajjad jafari,3 Bahman Mirzaei,4,* Mahdieh Hassani,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 aimed to investigate the synergistic effect of thymol/ampicillin on Escherichia coli (E. coli).
  • Methods: Antimicrobial effects of thymol and ampicillin individually and in combination with different concentrations on E. coli ATCC 25922 were performed by MIC-MBC method. The antimicrobial effect of a compound that had a synergistic effect on twenty clinical strains of E. coli bacteria was conducted by the MIC-MBC method, and the identification of chemical bonds, functional groups, and molecular interactions of this compound was investigated with an FT-IR device. Checkered method, time-killing curve and biofilm inhibition on E. coli ATCC 25922 bacteria, and investigation of cytotoxicity on human red blood cells (RBCs) by hemolysis method and human skin fibroblast cells (Ffk) with MTT method were performed. A1 compound had a synergistic effect
  • Results: The results of this study showed that the antimicrobial effects of thymol, ampicillin, and thymol/ampicillin (A1 compound) on E. coli ATCC 25922 were 256, 8, 8/2 µg/ml (FICI: 1), respectively. The antimicrobial effects of the A1 compound on clinical strains of E. coli were 128-512/32-64 µg/ml, respectively. The time curve for killing E. coli was higher in the combined mode than in the individual modes. These compounds had chemical bonds OH carbohydrates proteins, polyphenols, C=O amide I band, C-O-C polysaccharide, and C-N amide III band, but C=C conjugated, C≡C compound shows the connection between thymol/ampicillin. The biofilm inhibition rate of thymol, ampicillin, and thymol/ampicillin against E. coli bacteria was 29.69%, 60%, and 62%, respectively. The toxicity of thymol, ampicillin, and A1 compound against human RBCs were 36.12, 8.38, and 9.54, and against human Ffk cells were 9.92, 6.83, and 9.33 respectively.
  • Conclusion: Considering the resistance of ampicillin in the treatment of diseases caused by E. coli, the results of this study proved that thymol/ampicillin has high anti-bacterial and anti-biofilm properties. Toxicity on several cells was the same, and this compound can be tested later.
  • Keywords: Escherichia coli, Thymol, Ampicillin, Synergistic