In vitro experimental evaluation of the antibacterial, antibiotic-synergistic, and anti-motility effects of eugenol against clinical Pseudomonas aeruginosa isolates from hospitalized animals
- 1Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
- 2Department of Animal Science, Faculty of Agriculture, University of Kurdistan, Kurdistan, Iran
- 3Department of Microbiology, Faculty of Veterinary Medicine, Islamic Azad University, Karaj Branch, Karaj, Iran
Abstract
Background and Objectives:: Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen responsible for severe infections and increasing therapeutic difficulties due to multidrug resistance and virulence traits such as motility and biofilm formation. This study aimed to evaluate the in vitro antibacterial, antibiotic-synergistic, and anti-motility effects of eugenol in combination with cefixime and gentamicin against nine clinical P. aeruginosa isolates obtained from hospitalized animals.
Materials and Methods:: This preliminary in vitro laboratory investigation was conducted on a convenience sample of nine independent non-duplicate clinical P. aeruginosa isolates obtained from wound swabs and urinary tract samples of hospitalized animals at the Small Animal Hospital, Faculty of Veterinary Medicine, University of Tehran. Minimum inhibitory concentrations (MICs) of eugenol alone were determined across all nine isolates using the broth microdilution method in accordance with CLSI guidelines (M07-A11). Synergistic interactions between eugenol and the antibiotics cefixime and gentamicin were evaluated using the checkerboard assay and calculation of the fractional inhibitory concentration index (FICI) on a subset of three selected representative isolates (P3, P6, and P9). Furthermore, the effects of sub-inhibitory concentrations of eugenol (“MIC/2” ) on bacterial motility were assessed using standardized media containing 0.3%, 0.7%, and 1.5% agar to evaluate swimming, swarming, and twitching motilities, respectively, across this same subset of isolates (P3, P6, and P9) in biological triplicate (n=3).
Results:: Antimicrobial analysis across all nine isolates demonstrated intrinsic antibacterial activity of eugenol, with MIC values ranging from 2.5 to 10 μg/mL. Checkerboard synergy testing on the selected representative subset (P3, P6, and P9) revealed synergistic interactions with cefixime (“FICI”=0.5 for isolate P6, P3 and P9) as well as interactions with gentamicin yielding FICI values of 0.256 (for isolates P6 and P9) and 0.384 (for isolate P3), classifying these combinations within synergistic interaction ranges (“FICI”≤0.5). Additionally, sub-inhibitory eugenol treatment of the tested subset significantly reduced bacterial motility compared to untreated controls, decreasing swimming by 44–57%, swarming by 43–46%, and twitching by 39–64% (P<0.05).
Conclusion:: Eugenol demonstrated notable in vitro antibacterial and anti-motility activities against tested clinical P. aeruginosa isolates from veterinary sources, alongside favorable FICI interactions with gentamicin and cefixime. Because these findings are strictly restricted to limited in vitro laboratory observations without dosage optimization, toxicity, or in vivo efficacy evaluations, further comprehensive investigations are required before establishing any potential clinical relevance.
Related
- Experimental and computational evaluation of antiproliferative, antioxidant, and antibacterial activities of Commiphora terebinthina aerial parts
- MRSA-dominant colonization and synergistic pathogenicity with Pseudomonas aeruginosa in a polymicrobial bone infection model
- NIR-responsive carbon monoxide nanoplatform for synergistic antibacterial and anti-inflammatory therapy of refractory keratitis and biofilm-infected wounds
- Visible-Light-Enhanced Lanthanide Heterostructure with Synergistic Antibacterial and Anti-inflammatory Activity to Accelerate Wound Healing.
- Evaluation of Clinical SYNTAX Score in Predicting New-Onset Atrial Fibrillation and Long-Term Prognosis in Patients Hospitalized with Non-ST Segment Elevation Myocardial Infarction
BibTeX
@article{mostaan2026vitro,
title = {{In vitro experimental evaluation of the antibacterial, antibiotic-synergistic, and anti-motility effects of eugenol against clinical Pseudomonas aeruginosa isolates from hospitalized animals}},
author = {Seyedeh Samaneh Mostaan and Bahar Nayeri Fasaei and Aram Sharifi and Aghil Sharifzadeh and Iradj Ashrafi Tamai and Alireza Salmani Ghahyazi},
journal = {Iranian Journal of Microbiology},
year = {2026},
month = nov,
doi = {10.18502/ijm.v18i5.22874},
url = {https://doi.org/10.18502/ijm.v18i5.22874},
note = {CC BY-NC 4.0},
}
RIS
TY - JOUR
TI - In vitro experimental evaluation of the antibacterial, antibiotic-synergistic, and anti-motility effects of eugenol against clinical Pseudomonas aeruginosa isolates from hospitalized animals
AU - Seyedeh Samaneh Mostaan
AU - Bahar Nayeri Fasaei
AU - Aram Sharifi
AU - Aghil Sharifzadeh
AU - Iradj Ashrafi Tamai
AU - Alireza Salmani Ghahyazi
PY - 2026
DA - 2026/11/06
JO - Iranian Journal of Microbiology
DO - 10.18502/ijm.v18i5.22874
UR - https://doi.org/10.18502/ijm.v18i5.22874
AB - Background and Objectives:: Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen responsible for severe infections and increasing therapeutic difficulties due to multidrug resistance and virulence traits such as motility and biofilm formation. This study aimed to evaluate the in vitro antibacterial, antibiotic-synergistic, and anti-motility effects of eugenol in combination with cefixime and gentamicin against nine clinical P. aeruginosa isolates obtained from hospitalized animals. Materials and Methods:: This preliminary in vitro laboratory investigation was conducted on a convenience sample of nine independent non-duplicate clinical P. aeruginosa isolates obtained from wound swabs and urinary tract samples of hospitalized animals at the Small Animal Hospital, Faculty of Veterinary Medicine, University of Tehran. Minimum inhibitory concentrations (MICs) of eugenol alone were determined across all nine isolates using the broth microdilution method in accordance with CLSI guidelines (M07-A11). Synergistic interactions between eugenol and the antibiotics cefixime and gentamicin were evaluated using the checkerboard assay and calculation of the fractional inhibitory concentration index (FICI) on a subset of three selected representative isolates (P3, P6, and P9). Furthermore, the effects of sub-inhibitory concentrations of eugenol (“MIC/2” ) on bacterial motility were assessed using standardized media containing 0.3%, 0.7%, and 1.5% agar to evaluate swimming, swarming, and twitching motilities, respectively, across this same subset of isolates (P3, P6, and P9) in biological triplicate (n=3). Results:: Antimicrobial analysis across all nine isolates demonstrated intrinsic antibacterial activity of eugenol, with MIC values ranging from 2.5 to 10 μg/mL. Checkerboard synergy testing on the selected representative subset (P3, P6, and P9) revealed synergistic interactions with cefixime (“FICI”=0.5 for isolate P6, P3 and P9) as well as interactions with gentamicin yielding FICI values of 0.256 (for isolates P6 and P9) and 0.384 (for isolate P3), classifying these combinations within synergistic interaction ranges (“FICI”≤0.5). Additionally, sub-inhibitory eugenol treatment of the tested subset significantly reduced bacterial motility compared to untreated controls, decreasing swimming by 44–57%, swarming by 43–46%, and twitching by 39–64% (P<0.05). Conclusion:: Eugenol demonstrated notable in vitro antibacterial and anti-motility activities against tested clinical P. aeruginosa isolates from veterinary sources, alongside favorable FICI interactions with gentamicin and cefixime. Because these findings are strictly restricted to limited in vitro laboratory observations without dosage optimization, toxicity, or in vivo efficacy evaluations, further comprehensive investigations are required before establishing any potential clinical relevance.
SN - 2008-3289
SN - 2008-4447
ER -