In Vitro Antibacterial Potentials of Cinnamomum verum J. Presl (Cinnamon), Citrus x aurantium L. (Petitgrain) Pelargonium graveolens L'Hér (Rose Geranium), and Thymus vulgaris L. (Thyme) Essential Oil-Containing Ointments Against Canine Otitis Externa Pseudomonas aeruginosa Isolates.
8 affiliations
- 1Department of Medical Microbiology, Medical School, University of Pécs, H-7624 Pécs, Hungary.
- 2Department of Pharmacology and Toxicology, University of Veterinary Medicine, H-1078 Budapest, Hungary.
- 3National Laboratory of Infectious Animal Diseases, Antimicrobial Resistance, Veterinary Public Health and Food Chain Safety, University of Veterinary Medicine, H-1078 Budapest, Hungary.
- 4Department of Pharmacognosy, Faculty of Pharmacy, University of Pécs, H-7624 Pécs, Hungary.
- 5Department of Pharmacognosy, Faculty of Pharmacy, Semmelweiss University, H-1092 Budapest, Hungary.
- 6Center for Pharmacology and Drug Research & Development, Semmelweis University, Üllői u. 26, H-1085 Budapest, Hungary.
- 7Department of Clinical Centre, Institute of Clinical Pharmacy of Pécs, H-7624 Pécs, Hungary.
- 8Department of Medical Biology, Medical School, University of Pécs, H-7624 Pécs, Hungary.
Abstract
Background/Objectives: Otitis externa is a common infection in dogs. The most important aetiological agent is Pseudomonas aeruginosa, and an increasing number of cases are proving difficult to treat due to this pathogen's antibiotic resistance. Methods: We determined the composition of cinnamon (Cinnamomum verum J. Presl), petitgrain (Citrus x aurantium L.), rose geranium (Pelargonium graveolens L'Hér), and thyme (Thymus vulgaris L.) essential oils (EOs) using gas chromatography-mass spectrometry (GC-MS). We then used the bioautographic method to identify antibacterial components. Two-and-a-half- and five percent concentrations of the essential oils were added to four different ointment bases, such as hydrogelum methylcellulose, unguentum oleosum, unguentum stearini, and vaselinum cholesterinatum, and the in vitro antibacterial effects were tested on lawns of six P. aeruginosa isolates using the antibiotic-containing product Marbogen complex as a control. The keepability of the methylcellulose-based ointments was monitored at 4 °C and 27 °C for 12 months, with efficacy losses evaluated monthly. Results: Hydrogel methylcellulose (HM) was the most effective at supporting the therapeutic efficacy of each oil, reducing the bacterial count on the exposed area by 99.999%, 100%, 100%, and 100% in the case of 5% cinnamon, petitgrain, rose geranium, and thyme, respectively. EO-based HM ointments take effect within 15 min, with only slight improvement after 30, 45, and 60 min. Cinnamon was the most effective when applied in the HM matrix. In contrast to the HM and US gel matrices, the antibacterial supportive effects of Unguentum oleosum and Vazelinum cholestrinatum were drastically lower. The antimicrobial efficacy of essential oils in hydrogel formulation varied significantly depending on the type of oil (p < 0.001), its concentration (p < 0.001), the exposure time (p < 0.001), and the P. aeruginosa isolate used (p < 0.001). Cinnamon oil demonstrated the highest efficacy, achieving near-complete bacterial elimination across all isolates within 15 min. There was no significant difference between the 2.5% and 5% concentrations (EMM: 0.016 vs. 0.004; p = 0.904). Conclusions: Our results demonstrate that essential oil-based products can be effective alternatives to antibiotics when used in conjunction with an effective gel matrix.
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BibTeX
@article{seressteinbach2026vitro,
title = {{In Vitro Antibacterial Potentials of Cinnamomum verum J. Presl (Cinnamon), Citrus x aurantium L. (Petitgrain) Pelargonium graveolens L'Hér (Rose Geranium), and Thymus vulgaris L. (Thyme) Essential Oil-Containing Ointments Against Canine Otitis Externa Pseudomonas aeruginosa Isolates.}},
author = {Anita Seres-Steinbach and Ákos Jerzsele and Adrienn Mercedesz Veres and Viktória Balázs Lilla and Eszter Riethmüller and Boglárka Kiss and Krisztián Bányai and György Schneider},
journal = {Pharmaceuticals (Basel, Switzerland)},
year = {2026},
month = sep,
doi = {10.3390/ph19101500},
url = {https://europepmc.org/article/MED/42943197},
note = {CC BY},
}
RIS
TY - JOUR
TI - In Vitro Antibacterial Potentials of Cinnamomum verum J. Presl (Cinnamon), Citrus x aurantium L. (Petitgrain) Pelargonium graveolens L'Hér (Rose Geranium), and Thymus vulgaris L. (Thyme) Essential Oil-Containing Ointments Against Canine Otitis Externa Pseudomonas aeruginosa Isolates.
AU - Anita Seres-Steinbach
AU - Ákos Jerzsele
AU - Adrienn Mercedesz Veres
AU - Viktória Balázs Lilla
AU - Eszter Riethmüller
AU - Boglárka Kiss
AU - Krisztián Bányai
AU - György Schneider
PY - 2026
DA - 2026/09/22
JO - Pharmaceuticals (Basel, Switzerland)
DO - 10.3390/ph19101500
UR - https://europepmc.org/article/MED/42943197
AB - Background/Objectives: Otitis externa is a common infection in dogs. The most important aetiological agent is Pseudomonas aeruginosa, and an increasing number of cases are proving difficult to treat due to this pathogen's antibiotic resistance. Methods: We determined the composition of cinnamon (Cinnamomum verum J. Presl), petitgrain (Citrus x aurantium L.), rose geranium (Pelargonium graveolens L'Hér), and thyme (Thymus vulgaris L.) essential oils (EOs) using gas chromatography-mass spectrometry (GC-MS). We then used the bioautographic method to identify antibacterial components. Two-and-a-half- and five percent concentrations of the essential oils were added to four different ointment bases, such as hydrogelum methylcellulose, unguentum oleosum, unguentum stearini, and vaselinum cholesterinatum, and the in vitro antibacterial effects were tested on lawns of six P. aeruginosa isolates using the antibiotic-containing product Marbogen complex as a control. The keepability of the methylcellulose-based ointments was monitored at 4 °C and 27 °C for 12 months, with efficacy losses evaluated monthly. Results: Hydrogel methylcellulose (HM) was the most effective at supporting the therapeutic efficacy of each oil, reducing the bacterial count on the exposed area by 99.999%, 100%, 100%, and 100% in the case of 5% cinnamon, petitgrain, rose geranium, and thyme, respectively. EO-based HM ointments take effect within 15 min, with only slight improvement after 30, 45, and 60 min. Cinnamon was the most effective when applied in the HM matrix. In contrast to the HM and US gel matrices, the antibacterial supportive effects of Unguentum oleosum and Vazelinum cholestrinatum were drastically lower. The antimicrobial efficacy of essential oils in hydrogel formulation varied significantly depending on the type of oil (p < 0.001), its concentration (p < 0.001), the exposure time (p < 0.001), and the P. aeruginosa isolate used (p < 0.001). Cinnamon oil demonstrated the highest efficacy, achieving near-complete bacterial elimination across all isolates within 15 min. There was no significant difference between the 2.5% and 5% concentrations (EMM: 0.016 vs. 0.004; p = 0.904). Conclusions: Our results demonstrate that essential oil-based products can be effective alternatives to antibiotics when used in conjunction with an effective gel matrix.
SN - 1424-8247
ER -