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SYSTEMATIC REVIEW article

Front. Pharmacol.
Sec. Ethnopharmacology
Volume 15 - 2024 | doi: 10.3389/fphar.2024.1487083
This article is part of the Research Topic Unveiling the Future of Antibiotics: Exploring the WHO Priority List of Antibiotic-Resistant Bacteria for Discovery, Research, and Development of Novel Therapeutics View all articles

Thymol and Carvacrol Against Klebsiella, Anti-bacterial, Antibiofilm, and Synergistic activities: A Systematic Review

Provisionally accepted
Kousha Farhadi Kousha Farhadi 1Erta Rajabi Erta Rajabi 1Hesam Aldin Varpaei Hesam Aldin Varpaei 2Maryam Iranzadasl Maryam Iranzadasl 3Sepideh Khodaparast Sepideh Khodaparast 4Mohammadreza Salehi Mohammadreza Salehi 5,6*
  • 1 Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Alborz, Iran
  • 2 College of Nursing, Michigan State University, East Lansing, Michigan, United States
  • 3 Department of Traditional Medicine, School of Persian Medicine, Shahed University, Tehran, Alborz, Iran
  • 4 Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Alborz, Iran
  • 5 Department of Infectious Diseases, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
  • 6 Research Center for Antibiotic Stewardship & Antimicrobial Resistance, Department of Infectious Diseases, Imam Khomeini Hospital Complex, Tehran University of Medical sciences (TUMS), Tehran, Iran, Tehran, Alborz, Iran

The final, formatted version of the article will be published soon.

    Introduction: Klebsiella poses a significant global threat due to its high antibiotic resistance rate. In recent years, researchers have been seeking alternative antimicrobial agents, leading to the introduction of natural compounds such as monoterpenes, specifically thymol and carvacrol. This review aims to illustrate the potential antimicrobial, anti-biofilm, and synergistic traits of thymol and carvacrol in combat against Klebsiella. Methods: Searching PubMed, Scopus, and Web of Science, we reviewed available evidence on the antibacterial effects of thymol, carvacrol, or combined with other compounds against Klebsiella until May 2024. Reference checking was performed after the inclusion of studies. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), fractional inhibitory concentration (FIC), and anti-biofilm activity were gathered, and MBC/MIC ratio was calculated to assess the bactericidal efficacy. Results: We retrieved 38 articles out of 2,652 studies screened. The gathered data assessed anti-microbial activity of thymol, carvacrol, and both compounds in a total of 17, 10, and 11 studies, respectively. The mean (± standard deviation) non-weighted MIC was 475.46 µg/ml (±509.95) out of 60 MIC for thymol and 279.26 µg/ml (±434.38) out of 68 MIC for carvacrol. Thymol and carvacrol showed anti-biofilm activities in the forms of disruption, inhibition, and mass reduction of biofilms. The MBC/MIC ratio was lower than 4 in 45 out of 47 cases, showing high bactericidal efficacy. FIC values were gathered for 68 combinations of thymol and carvacrol with other compounds, and they were mostly synergistic or additive. Conclusion: Thymol and carvacrol alone or in combination with other compounds, specifically known antibiotics, show great antimicrobial activity.

    Keywords: Klebsiella1, K. pneumoniae2, antimicrobial resistance3, Thymol4, Carvacrol5, Synergistic6, Biofilm7 Font: (Default) Times New Roman, 12 pt

    Received: 27 Aug 2024; Accepted: 04 Oct 2024.

    Copyright: © 2024 Farhadi, Rajabi, Varpaei, Iranzadasl, Khodaparast and Salehi. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Mohammadreza Salehi, Department of Infectious Diseases, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran

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